1 /*
   2  * Copyright (c) 1994, 2017, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 package java.lang;
  26 
  27 import java.io.BufferedInputStream;
  28 import java.io.BufferedOutputStream;
  29 import java.io.Console;
  30 import java.io.FileDescriptor;
  31 import java.io.FileInputStream;
  32 import java.io.FileOutputStream;
  33 import java.io.IOException;
  34 import java.io.InputStream;
  35 import java.io.PrintStream;
  36 import java.io.UnsupportedEncodingException;
  37 import java.lang.annotation.Annotation;
  38 import java.lang.module.ModuleDescriptor;
  39 import java.lang.reflect.Constructor;
  40 import java.lang.reflect.Executable;
  41 import java.lang.reflect.Method;
  42 import java.lang.reflect.Modifier;
  43 import java.net.URI;
  44 import java.security.AccessControlContext;
  45 import java.security.ProtectionDomain;
  46 import java.security.AccessController;
  47 import java.security.PrivilegedAction;
  48 import java.nio.channels.Channel;
  49 import java.nio.channels.spi.SelectorProvider;
  50 import java.util.Iterator;
  51 import java.util.List;
  52 import java.util.Map;
  53 import java.util.Objects;
  54 import java.util.Properties;
  55 import java.util.PropertyPermission;
  56 import java.util.ResourceBundle;
  57 import java.util.function.Supplier;
  58 import java.util.concurrent.ConcurrentHashMap;
  59 import java.util.stream.Stream;
  60 
  61 import jdk.internal.module.ModuleBootstrap;
  62 import jdk.internal.module.ServicesCatalog;
  63 import jdk.internal.reflect.CallerSensitive;
  64 import jdk.internal.reflect.Reflection;
  65 import jdk.internal.HotSpotIntrinsicCandidate;
  66 import jdk.internal.misc.JavaLangAccess;
  67 import jdk.internal.misc.SharedSecrets;
  68 import jdk.internal.misc.VM;
  69 import jdk.internal.logger.LoggerFinderLoader;
  70 import jdk.internal.logger.LazyLoggers;
  71 import jdk.internal.logger.LocalizedLoggerWrapper;
  72 import sun.reflect.annotation.AnnotationType;
  73 import sun.nio.ch.Interruptible;
  74 import sun.security.util.SecurityConstants;
  75 
  76 /**
  77  * The <code>System</code> class contains several useful class fields
  78  * and methods. It cannot be instantiated.
  79  *
  80  * <p>Among the facilities provided by the <code>System</code> class
  81  * are standard input, standard output, and error output streams;
  82  * access to externally defined properties and environment
  83  * variables; a means of loading files and libraries; and a utility
  84  * method for quickly copying a portion of an array.
  85  *
  86  * @author  unascribed
  87  * @since   1.0
  88  */
  89 public final class System {
  90     /* register the natives via the static initializer.
  91      *
  92      * VM will invoke the initializeSystemClass method to complete
  93      * the initialization for this class separated from clinit.
  94      * Note that to use properties set by the VM, see the constraints
  95      * described in the initializeSystemClass method.
  96      */
  97     private static native void registerNatives();
  98     static {
  99         registerNatives();
 100     }
 101 
 102     /** Don't let anyone instantiate this class */
 103     private System() {
 104     }
 105 
 106     /**
 107      * The "standard" input stream. This stream is already
 108      * open and ready to supply input data. Typically this stream
 109      * corresponds to keyboard input or another input source specified by
 110      * the host environment or user.
 111      */
 112     public static final InputStream in = null;
 113 
 114     /**
 115      * The "standard" output stream. This stream is already
 116      * open and ready to accept output data. Typically this stream
 117      * corresponds to display output or another output destination
 118      * specified by the host environment or user.
 119      * <p>
 120      * For simple stand-alone Java applications, a typical way to write
 121      * a line of output data is:
 122      * <blockquote><pre>
 123      *     System.out.println(data)
 124      * </pre></blockquote>
 125      * <p>
 126      * See the <code>println</code> methods in class <code>PrintStream</code>.
 127      *
 128      * @see     java.io.PrintStream#println()
 129      * @see     java.io.PrintStream#println(boolean)
 130      * @see     java.io.PrintStream#println(char)
 131      * @see     java.io.PrintStream#println(char[])
 132      * @see     java.io.PrintStream#println(double)
 133      * @see     java.io.PrintStream#println(float)
 134      * @see     java.io.PrintStream#println(int)
 135      * @see     java.io.PrintStream#println(long)
 136      * @see     java.io.PrintStream#println(java.lang.Object)
 137      * @see     java.io.PrintStream#println(java.lang.String)
 138      */
 139     public static final PrintStream out = null;
 140 
 141     /**
 142      * The "standard" error output stream. This stream is already
 143      * open and ready to accept output data.
 144      * <p>
 145      * Typically this stream corresponds to display output or another
 146      * output destination specified by the host environment or user. By
 147      * convention, this output stream is used to display error messages
 148      * or other information that should come to the immediate attention
 149      * of a user even if the principal output stream, the value of the
 150      * variable <code>out</code>, has been redirected to a file or other
 151      * destination that is typically not continuously monitored.
 152      */
 153     public static final PrintStream err = null;
 154 
 155     /* The security manager for the system.
 156      */
 157     private static volatile SecurityManager security;
 158 
 159     /**
 160      * Reassigns the "standard" input stream.
 161      *
 162      * <p>First, if there is a security manager, its <code>checkPermission</code>
 163      * method is called with a <code>RuntimePermission("setIO")</code> permission
 164      *  to see if it's ok to reassign the "standard" input stream.
 165      *
 166      * @param in the new standard input stream.
 167      *
 168      * @throws SecurityException
 169      *        if a security manager exists and its
 170      *        <code>checkPermission</code> method doesn't allow
 171      *        reassigning of the standard input stream.
 172      *
 173      * @see SecurityManager#checkPermission
 174      * @see java.lang.RuntimePermission
 175      *
 176      * @since   1.1
 177      */
 178     public static void setIn(InputStream in) {
 179         checkIO();
 180         setIn0(in);
 181     }
 182 
 183     /**
 184      * Reassigns the "standard" output stream.
 185      *
 186      * <p>First, if there is a security manager, its <code>checkPermission</code>
 187      * method is called with a <code>RuntimePermission("setIO")</code> permission
 188      *  to see if it's ok to reassign the "standard" output stream.
 189      *
 190      * @param out the new standard output stream
 191      *
 192      * @throws SecurityException
 193      *        if a security manager exists and its
 194      *        <code>checkPermission</code> method doesn't allow
 195      *        reassigning of the standard output stream.
 196      *
 197      * @see SecurityManager#checkPermission
 198      * @see java.lang.RuntimePermission
 199      *
 200      * @since   1.1
 201      */
 202     public static void setOut(PrintStream out) {
 203         checkIO();
 204         setOut0(out);
 205     }
 206 
 207     /**
 208      * Reassigns the "standard" error output stream.
 209      *
 210      * <p>First, if there is a security manager, its <code>checkPermission</code>
 211      * method is called with a <code>RuntimePermission("setIO")</code> permission
 212      *  to see if it's ok to reassign the "standard" error output stream.
 213      *
 214      * @param err the new standard error output stream.
 215      *
 216      * @throws SecurityException
 217      *        if a security manager exists and its
 218      *        <code>checkPermission</code> method doesn't allow
 219      *        reassigning of the standard error output stream.
 220      *
 221      * @see SecurityManager#checkPermission
 222      * @see java.lang.RuntimePermission
 223      *
 224      * @since   1.1
 225      */
 226     public static void setErr(PrintStream err) {
 227         checkIO();
 228         setErr0(err);
 229     }
 230 
 231     private static volatile Console cons;
 232     /**
 233      * Returns the unique {@link java.io.Console Console} object associated
 234      * with the current Java virtual machine, if any.
 235      *
 236      * @return  The system console, if any, otherwise {@code null}.
 237      *
 238      * @since   1.6
 239      */
 240      public static Console console() {
 241          Console c;
 242          if ((c = cons) == null) {
 243              synchronized (System.class) {
 244                  if ((c = cons) == null) {
 245                      cons = c = SharedSecrets.getJavaIOAccess().console();
 246                  }
 247              }
 248          }
 249          return c;
 250      }
 251 
 252     /**
 253      * Returns the channel inherited from the entity that created this
 254      * Java virtual machine.
 255      *
 256      * <p> This method returns the channel obtained by invoking the
 257      * {@link java.nio.channels.spi.SelectorProvider#inheritedChannel
 258      * inheritedChannel} method of the system-wide default
 259      * {@link java.nio.channels.spi.SelectorProvider} object. </p>
 260      *
 261      * <p> In addition to the network-oriented channels described in
 262      * {@link java.nio.channels.spi.SelectorProvider#inheritedChannel
 263      * inheritedChannel}, this method may return other kinds of
 264      * channels in the future.
 265      *
 266      * @return  The inherited channel, if any, otherwise {@code null}.
 267      *
 268      * @throws  IOException
 269      *          If an I/O error occurs
 270      *
 271      * @throws  SecurityException
 272      *          If a security manager is present and it does not
 273      *          permit access to the channel.
 274      *
 275      * @since 1.5
 276      */
 277     public static Channel inheritedChannel() throws IOException {
 278         return SelectorProvider.provider().inheritedChannel();
 279     }
 280 
 281     private static void checkIO() {
 282         SecurityManager sm = getSecurityManager();
 283         if (sm != null) {
 284             sm.checkPermission(new RuntimePermission("setIO"));
 285         }
 286     }
 287 
 288     private static native void setIn0(InputStream in);
 289     private static native void setOut0(PrintStream out);
 290     private static native void setErr0(PrintStream err);
 291 
 292     /**
 293      * Sets the System security.
 294      *
 295      * <p> If there is a security manager already installed, this method first
 296      * calls the security manager's <code>checkPermission</code> method
 297      * with a <code>RuntimePermission("setSecurityManager")</code>
 298      * permission to ensure it's ok to replace the existing
 299      * security manager.
 300      * This may result in throwing a <code>SecurityException</code>.
 301      *
 302      * <p> Otherwise, the argument is established as the current
 303      * security manager. If the argument is <code>null</code> and no
 304      * security manager has been established, then no action is taken and
 305      * the method simply returns.
 306      *
 307      * @param      s   the security manager.
 308      * @exception  SecurityException  if the security manager has already
 309      *             been set and its <code>checkPermission</code> method
 310      *             doesn't allow it to be replaced.
 311      * @see #getSecurityManager
 312      * @see SecurityManager#checkPermission
 313      * @see java.lang.RuntimePermission
 314      */
 315     public static void setSecurityManager(final SecurityManager s) {
 316         if (security == null) {
 317             // ensure image reader is initialized
 318             Object.class.getResource("java/lang/ANY");
 319         }
 320         if (s != null) {
 321             try {
 322                 s.checkPackageAccess("java.lang");
 323             } catch (Exception e) {
 324                 // no-op
 325             }
 326         }
 327         setSecurityManager0(s);
 328     }
 329 
 330     private static synchronized
 331     void setSecurityManager0(final SecurityManager s) {
 332         SecurityManager sm = getSecurityManager();
 333         if (sm != null) {
 334             // ask the currently installed security manager if we
 335             // can replace it.
 336             sm.checkPermission(new RuntimePermission
 337                                      ("setSecurityManager"));
 338         }
 339 
 340         if ((s != null) && (s.getClass().getClassLoader() != null)) {
 341             // New security manager class is not on bootstrap classpath.
 342             // Cause policy to get initialized before we install the new
 343             // security manager, in order to prevent infinite loops when
 344             // trying to initialize the policy (which usually involves
 345             // accessing some security and/or system properties, which in turn
 346             // calls the installed security manager's checkPermission method
 347             // which will loop infinitely if there is a non-system class
 348             // (in this case: the new security manager class) on the stack).
 349             AccessController.doPrivileged(new PrivilegedAction<>() {
 350                 public Object run() {
 351                     s.getClass().getProtectionDomain().implies
 352                         (SecurityConstants.ALL_PERMISSION);
 353                     return null;
 354                 }
 355             });
 356         }
 357 
 358         security = s;
 359     }
 360 
 361     /**
 362      * Gets the system security interface.
 363      *
 364      * @return  if a security manager has already been established for the
 365      *          current application, then that security manager is returned;
 366      *          otherwise, <code>null</code> is returned.
 367      * @see     #setSecurityManager
 368      */
 369     public static SecurityManager getSecurityManager() {
 370         return security;
 371     }
 372 
 373     /**
 374      * Returns the current time in milliseconds.  Note that
 375      * while the unit of time of the return value is a millisecond,
 376      * the granularity of the value depends on the underlying
 377      * operating system and may be larger.  For example, many
 378      * operating systems measure time in units of tens of
 379      * milliseconds.
 380      *
 381      * <p> See the description of the class <code>Date</code> for
 382      * a discussion of slight discrepancies that may arise between
 383      * "computer time" and coordinated universal time (UTC).
 384      *
 385      * @return  the difference, measured in milliseconds, between
 386      *          the current time and midnight, January 1, 1970 UTC.
 387      * @see     java.util.Date
 388      */
 389     @HotSpotIntrinsicCandidate
 390     public static native long currentTimeMillis();
 391 
 392     /**
 393      * Returns the current value of the running Java Virtual Machine's
 394      * high-resolution time source, in nanoseconds.
 395      *
 396      * <p>This method can only be used to measure elapsed time and is
 397      * not related to any other notion of system or wall-clock time.
 398      * The value returned represents nanoseconds since some fixed but
 399      * arbitrary <i>origin</i> time (perhaps in the future, so values
 400      * may be negative).  The same origin is used by all invocations of
 401      * this method in an instance of a Java virtual machine; other
 402      * virtual machine instances are likely to use a different origin.
 403      *
 404      * <p>This method provides nanosecond precision, but not necessarily
 405      * nanosecond resolution (that is, how frequently the value changes)
 406      * - no guarantees are made except that the resolution is at least as
 407      * good as that of {@link #currentTimeMillis()}.
 408      *
 409      * <p>Differences in successive calls that span greater than
 410      * approximately 292 years (2<sup>63</sup> nanoseconds) will not
 411      * correctly compute elapsed time due to numerical overflow.
 412      *
 413      * <p>The values returned by this method become meaningful only when
 414      * the difference between two such values, obtained within the same
 415      * instance of a Java virtual machine, is computed.
 416      *
 417      * <p>For example, to measure how long some code takes to execute:
 418      * <pre> {@code
 419      * long startTime = System.nanoTime();
 420      * // ... the code being measured ...
 421      * long elapsedNanos = System.nanoTime() - startTime;}</pre>
 422      *
 423      * <p>To compare elapsed time against a timeout, use <pre> {@code
 424      * if (System.nanoTime() - startTime >= timeoutNanos) ...}</pre>
 425      * instead of <pre> {@code
 426      * if (System.nanoTime() >= startTime + timeoutNanos) ...}</pre>
 427      * because of the possibility of numerical overflow.
 428      *
 429      * @return the current value of the running Java Virtual Machine's
 430      *         high-resolution time source, in nanoseconds
 431      * @since 1.5
 432      */
 433     @HotSpotIntrinsicCandidate
 434     public static native long nanoTime();
 435 
 436     /**
 437      * Copies an array from the specified source array, beginning at the
 438      * specified position, to the specified position of the destination array.
 439      * A subsequence of array components are copied from the source
 440      * array referenced by <code>src</code> to the destination array
 441      * referenced by <code>dest</code>. The number of components copied is
 442      * equal to the <code>length</code> argument. The components at
 443      * positions <code>srcPos</code> through
 444      * <code>srcPos+length-1</code> in the source array are copied into
 445      * positions <code>destPos</code> through
 446      * <code>destPos+length-1</code>, respectively, of the destination
 447      * array.
 448      * <p>
 449      * If the <code>src</code> and <code>dest</code> arguments refer to the
 450      * same array object, then the copying is performed as if the
 451      * components at positions <code>srcPos</code> through
 452      * <code>srcPos+length-1</code> were first copied to a temporary
 453      * array with <code>length</code> components and then the contents of
 454      * the temporary array were copied into positions
 455      * <code>destPos</code> through <code>destPos+length-1</code> of the
 456      * destination array.
 457      * <p>
 458      * If <code>dest</code> is <code>null</code>, then a
 459      * <code>NullPointerException</code> is thrown.
 460      * <p>
 461      * If <code>src</code> is <code>null</code>, then a
 462      * <code>NullPointerException</code> is thrown and the destination
 463      * array is not modified.
 464      * <p>
 465      * Otherwise, if any of the following is true, an
 466      * <code>ArrayStoreException</code> is thrown and the destination is
 467      * not modified:
 468      * <ul>
 469      * <li>The <code>src</code> argument refers to an object that is not an
 470      *     array.
 471      * <li>The <code>dest</code> argument refers to an object that is not an
 472      *     array.
 473      * <li>The <code>src</code> argument and <code>dest</code> argument refer
 474      *     to arrays whose component types are different primitive types.
 475      * <li>The <code>src</code> argument refers to an array with a primitive
 476      *    component type and the <code>dest</code> argument refers to an array
 477      *     with a reference component type.
 478      * <li>The <code>src</code> argument refers to an array with a reference
 479      *    component type and the <code>dest</code> argument refers to an array
 480      *     with a primitive component type.
 481      * </ul>
 482      * <p>
 483      * Otherwise, if any of the following is true, an
 484      * <code>IndexOutOfBoundsException</code> is
 485      * thrown and the destination is not modified:
 486      * <ul>
 487      * <li>The <code>srcPos</code> argument is negative.
 488      * <li>The <code>destPos</code> argument is negative.
 489      * <li>The <code>length</code> argument is negative.
 490      * <li><code>srcPos+length</code> is greater than
 491      *     <code>src.length</code>, the length of the source array.
 492      * <li><code>destPos+length</code> is greater than
 493      *     <code>dest.length</code>, the length of the destination array.
 494      * </ul>
 495      * <p>
 496      * Otherwise, if any actual component of the source array from
 497      * position <code>srcPos</code> through
 498      * <code>srcPos+length-1</code> cannot be converted to the component
 499      * type of the destination array by assignment conversion, an
 500      * <code>ArrayStoreException</code> is thrown. In this case, let
 501      * <b><i>k</i></b> be the smallest nonnegative integer less than
 502      * length such that <code>src[srcPos+</code><i>k</i><code>]</code>
 503      * cannot be converted to the component type of the destination
 504      * array; when the exception is thrown, source array components from
 505      * positions <code>srcPos</code> through
 506      * <code>srcPos+</code><i>k</i><code>-1</code>
 507      * will already have been copied to destination array positions
 508      * <code>destPos</code> through
 509      * <code>destPos+</code><i>k</I><code>-1</code> and no other
 510      * positions of the destination array will have been modified.
 511      * (Because of the restrictions already itemized, this
 512      * paragraph effectively applies only to the situation where both
 513      * arrays have component types that are reference types.)
 514      *
 515      * @param      src      the source array.
 516      * @param      srcPos   starting position in the source array.
 517      * @param      dest     the destination array.
 518      * @param      destPos  starting position in the destination data.
 519      * @param      length   the number of array elements to be copied.
 520      * @exception  IndexOutOfBoundsException  if copying would cause
 521      *               access of data outside array bounds.
 522      * @exception  ArrayStoreException  if an element in the <code>src</code>
 523      *               array could not be stored into the <code>dest</code> array
 524      *               because of a type mismatch.
 525      * @exception  NullPointerException if either <code>src</code> or
 526      *               <code>dest</code> is <code>null</code>.
 527      */
 528     @HotSpotIntrinsicCandidate
 529     public static native void arraycopy(Object src,  int  srcPos,
 530                                         Object dest, int destPos,
 531                                         int length);
 532 
 533     /**
 534      * Returns the same hash code for the given object as
 535      * would be returned by the default method hashCode(),
 536      * whether or not the given object's class overrides
 537      * hashCode().
 538      * The hash code for the null reference is zero.
 539      *
 540      * @param x object for which the hashCode is to be calculated
 541      * @return  the hashCode
 542      * @since   1.1
 543      * @see Object#hashCode
 544      * @see java.util.Objects#hashCode(Object)
 545      */
 546     @HotSpotIntrinsicCandidate
 547     public static native int identityHashCode(Object x);
 548 
 549     /**
 550      * System properties. The following properties are guaranteed to be defined:
 551      * <dl>
 552      * <dt>java.version         <dd>Java version number
 553      * <dt>java.version.date    <dd>Java version date
 554      * <dt>java.vendor          <dd>Java vendor specific string
 555      * <dt>java.vendor.url      <dd>Java vendor URL
 556      * <dt>java.vendor.version  <dd>Java vendor version
 557      * <dt>java.home            <dd>Java installation directory
 558      * <dt>java.class.version   <dd>Java class version number
 559      * <dt>java.class.path      <dd>Java classpath
 560      * <dt>os.name              <dd>Operating System Name
 561      * <dt>os.arch              <dd>Operating System Architecture
 562      * <dt>os.version           <dd>Operating System Version
 563      * <dt>file.separator       <dd>File separator ("/" on Unix)
 564      * <dt>path.separator       <dd>Path separator (":" on Unix)
 565      * <dt>line.separator       <dd>Line separator ("\n" on Unix)
 566      * <dt>user.name            <dd>User account name
 567      * <dt>user.home            <dd>User home directory
 568      * <dt>user.dir             <dd>User's current working directory
 569      * </dl>
 570      */
 571 
 572     private static Properties props;
 573     private static native Properties initProperties(Properties props);
 574 
 575     /**
 576      * Determines the current system properties.
 577      * <p>
 578      * First, if there is a security manager, its
 579      * <code>checkPropertiesAccess</code> method is called with no
 580      * arguments. This may result in a security exception.
 581      * <p>
 582      * The current set of system properties for use by the
 583      * {@link #getProperty(String)} method is returned as a
 584      * <code>Properties</code> object. If there is no current set of
 585      * system properties, a set of system properties is first created and
 586      * initialized. This set of system properties always includes values
 587      * for the following keys:
 588      * <table class="striped" style="text-align:left">
 589      * <caption style="display:none">Shows property keys and associated values</caption>
 590      * <thead>
 591      * <tr><th scope="col">Key</th>
 592      *     <th scope="col">Description of Associated Value</th></tr>
 593      * </thead>
 594      * <tbody>
 595      * <tr><th scope="row"><code>java.version</code></th>
 596      *     <td>Java Runtime Environment version, which may be interpreted
 597      *     as a {@link Runtime.Version}</td></tr>
 598      * <tr><th scope="row"><code>java.version.date</code></th>
 599      *     <td>Java Runtime Environment version date, in ISO-8601 YYYY-MM-DD
 600      *     format, which may be interpreted as a {@link
 601      *     java.time.LocalDate}</td></tr>
 602      * <tr><th scope="row"><code>java.vendor</code></th>
 603      *     <td>Java Runtime Environment vendor</td></tr>
 604      * <tr><th scope="row"><code>java.vendor.url</code></th>
 605      *     <td>Java vendor URL</td></tr>
 606      * <tr><th scope="row"><code>java.vendor.version</code></th>
 607      *     <td>Java vendor version</td></tr>
 608      * <tr><th scope="row"><code>java.home</code></th>
 609      *     <td>Java installation directory</td></tr>
 610      * <tr><th scope="row"><code>java.vm.specification.version</code></th>
 611      *     <td>Java Virtual Machine specification version which may be
 612      *     interpreted as a {@link Runtime.Version}</td></tr>
 613      * <tr><th scope="row"><code>java.vm.specification.vendor</code></th>
 614      *     <td>Java Virtual Machine specification vendor</td></tr>
 615      * <tr><th scope="row"><code>java.vm.specification.name</code></th>
 616      *     <td>Java Virtual Machine specification name</td></tr>
 617      * <tr><th scope="row"><code>java.vm.version</code></th>
 618      *     <td>Java Virtual Machine implementation version which may be
 619      *     interpreted as a {@link Runtime.Version}</td></tr>
 620      * <tr><th scope="row"><code>java.vm.vendor</code></th>
 621      *     <td>Java Virtual Machine implementation vendor</td></tr>
 622      * <tr><th scope="row"><code>java.vm.name</code></th>
 623      *     <td>Java Virtual Machine implementation name</td></tr>
 624      * <tr><th scope="row"><code>java.specification.version</code></th>
 625      *     <td>Java Runtime Environment specification version which may be
 626      *     interpreted as a {@link Runtime.Version}</td></tr>
 627      * <tr><th scope="row"><code>java.specification.vendor</code></th>
 628      *     <td>Java Runtime Environment specification  vendor</td></tr>
 629      * <tr><th scope="row"><code>java.specification.name</code></th>
 630      *     <td>Java Runtime Environment specification  name</td></tr>
 631      * <tr><th scope="row"><code>java.class.version</code></th>
 632      *     <td>Java class format version number</td></tr>
 633      * <tr><th scope="row"><code>java.class.path</code></th>
 634      *     <td>Java class path  (refer to
 635      *        {@link ClassLoader#getSystemClassLoader()} for details)</td></tr>
 636      * <tr><th scope="row"><code>java.library.path</code></th>
 637      *     <td>List of paths to search when loading libraries</td></tr>
 638      * <tr><th scope="row"><code>java.io.tmpdir</code></th>
 639      *     <td>Default temp file path</td></tr>
 640      * <tr><th scope="row"><code>java.compiler</code></th>
 641      *     <td>Name of JIT compiler to use</td></tr>
 642      * <tr><th scope="row"><code>os.name</code></th>
 643      *     <td>Operating system name</td></tr>
 644      * <tr><th scope="row"><code>os.arch</code></th>
 645      *     <td>Operating system architecture</td></tr>
 646      * <tr><th scope="row"><code>os.version</code></th>
 647      *     <td>Operating system version</td></tr>
 648      * <tr><th scope="row"><code>file.separator</code></th>
 649      *     <td>File separator ("/" on UNIX)</td></tr>
 650      * <tr><th scope="row"><code>path.separator</code></th>
 651      *     <td>Path separator (":" on UNIX)</td></tr>
 652      * <tr><th scope="row"><code>line.separator</code></th>
 653      *     <td>Line separator ("\n" on UNIX)</td></tr>
 654      * <tr><th scope="row"><code>user.name</code></th>
 655      *     <td>User's account name</td></tr>
 656      * <tr><th scope="row"><code>user.home</code></th>
 657      *     <td>User's home directory</td></tr>
 658      * <tr><th scope="row"><code>user.dir</code></th>
 659      *     <td>User's current working directory</td></tr>
 660      * </tbody>
 661      * </table>
 662      * <p>
 663      * Multiple paths in a system property value are separated by the path
 664      * separator character of the platform.
 665      * <p>
 666      * Note that even if the security manager does not permit the
 667      * <code>getProperties</code> operation, it may choose to permit the
 668      * {@link #getProperty(String)} operation.
 669      *
 670      * @implNote In addition to the standard system properties, the system
 671      * properties may include the following keys:
 672      * <table class="striped">
 673      * <caption style="display:none">Shows property keys and associated values</caption>
 674      * <thead>
 675      * <tr><th scope="col">Key</th>
 676      *     <th scope="col">Description of Associated Value</th></tr>
 677      * </thead>
 678      * <tbody>
 679      * <tr><th scope="row">{@code jdk.module.path}</th>
 680      *     <td>The application module path</td></tr>
 681      * <tr><th scope="row">{@code jdk.module.upgrade.path}</th>
 682      *     <td>The upgrade module path</td></tr>
 683      * <tr><th scope="row">{@code jdk.module.main}</th>
 684      *     <td>The module name of the initial/main module</td></tr>
 685      * <tr><th scope="row">{@code jdk.module.main.class}</th>
 686      *     <td>The main class name of the initial module</td></tr>
 687      * </tbody>
 688      * </table>
 689      *
 690      * @return     the system properties
 691      * @exception  SecurityException  if a security manager exists and its
 692      *             <code>checkPropertiesAccess</code> method doesn't allow access
 693      *              to the system properties.
 694      * @see        #setProperties
 695      * @see        java.lang.SecurityException
 696      * @see        java.lang.SecurityManager#checkPropertiesAccess()
 697      * @see        java.util.Properties
 698      */
 699     public static Properties getProperties() {
 700         SecurityManager sm = getSecurityManager();
 701         if (sm != null) {
 702             sm.checkPropertiesAccess();
 703         }
 704 
 705         return props;
 706     }
 707 
 708     /**
 709      * Returns the system-dependent line separator string.  It always
 710      * returns the same value - the initial value of the {@linkplain
 711      * #getProperty(String) system property} {@code line.separator}.
 712      *
 713      * <p>On UNIX systems, it returns {@code "\n"}; on Microsoft
 714      * Windows systems it returns {@code "\r\n"}.
 715      *
 716      * @return the system-dependent line separator string
 717      * @since 1.7
 718      */
 719     public static String lineSeparator() {
 720         return lineSeparator;
 721     }
 722 
 723     private static String lineSeparator;
 724 
 725     /**
 726      * Sets the system properties to the <code>Properties</code>
 727      * argument.
 728      * <p>
 729      * First, if there is a security manager, its
 730      * <code>checkPropertiesAccess</code> method is called with no
 731      * arguments. This may result in a security exception.
 732      * <p>
 733      * The argument becomes the current set of system properties for use
 734      * by the {@link #getProperty(String)} method. If the argument is
 735      * <code>null</code>, then the current set of system properties is
 736      * forgotten.
 737      *
 738      * @param      props   the new system properties.
 739      * @exception  SecurityException  if a security manager exists and its
 740      *             <code>checkPropertiesAccess</code> method doesn't allow access
 741      *              to the system properties.
 742      * @see        #getProperties
 743      * @see        java.util.Properties
 744      * @see        java.lang.SecurityException
 745      * @see        java.lang.SecurityManager#checkPropertiesAccess()
 746      */
 747     public static void setProperties(Properties props) {
 748         SecurityManager sm = getSecurityManager();
 749         if (sm != null) {
 750             sm.checkPropertiesAccess();
 751         }
 752         if (props == null) {
 753             props = new Properties();
 754             initProperties(props);
 755         }
 756         System.props = props;
 757     }
 758 
 759     /**
 760      * Gets the system property indicated by the specified key.
 761      * <p>
 762      * First, if there is a security manager, its
 763      * <code>checkPropertyAccess</code> method is called with the key as
 764      * its argument. This may result in a SecurityException.
 765      * <p>
 766      * If there is no current set of system properties, a set of system
 767      * properties is first created and initialized in the same manner as
 768      * for the <code>getProperties</code> method.
 769      *
 770      * @param      key   the name of the system property.
 771      * @return     the string value of the system property,
 772      *             or <code>null</code> if there is no property with that key.
 773      *
 774      * @exception  SecurityException  if a security manager exists and its
 775      *             <code>checkPropertyAccess</code> method doesn't allow
 776      *              access to the specified system property.
 777      * @exception  NullPointerException if <code>key</code> is
 778      *             <code>null</code>.
 779      * @exception  IllegalArgumentException if <code>key</code> is empty.
 780      * @see        #setProperty
 781      * @see        java.lang.SecurityException
 782      * @see        java.lang.SecurityManager#checkPropertyAccess(java.lang.String)
 783      * @see        java.lang.System#getProperties()
 784      */
 785     public static String getProperty(String key) {
 786         checkKey(key);
 787         SecurityManager sm = getSecurityManager();
 788         if (sm != null) {
 789             sm.checkPropertyAccess(key);
 790         }
 791 
 792         return props.getProperty(key);
 793     }
 794 
 795     /**
 796      * Gets the system property indicated by the specified key.
 797      * <p>
 798      * First, if there is a security manager, its
 799      * <code>checkPropertyAccess</code> method is called with the
 800      * <code>key</code> as its argument.
 801      * <p>
 802      * If there is no current set of system properties, a set of system
 803      * properties is first created and initialized in the same manner as
 804      * for the <code>getProperties</code> method.
 805      *
 806      * @param      key   the name of the system property.
 807      * @param      def   a default value.
 808      * @return     the string value of the system property,
 809      *             or the default value if there is no property with that key.
 810      *
 811      * @exception  SecurityException  if a security manager exists and its
 812      *             <code>checkPropertyAccess</code> method doesn't allow
 813      *             access to the specified system property.
 814      * @exception  NullPointerException if <code>key</code> is
 815      *             <code>null</code>.
 816      * @exception  IllegalArgumentException if <code>key</code> is empty.
 817      * @see        #setProperty
 818      * @see        java.lang.SecurityManager#checkPropertyAccess(java.lang.String)
 819      * @see        java.lang.System#getProperties()
 820      */
 821     public static String getProperty(String key, String def) {
 822         checkKey(key);
 823         SecurityManager sm = getSecurityManager();
 824         if (sm != null) {
 825             sm.checkPropertyAccess(key);
 826         }
 827 
 828         return props.getProperty(key, def);
 829     }
 830 
 831     /**
 832      * Sets the system property indicated by the specified key.
 833      * <p>
 834      * First, if a security manager exists, its
 835      * <code>SecurityManager.checkPermission</code> method
 836      * is called with a <code>PropertyPermission(key, "write")</code>
 837      * permission. This may result in a SecurityException being thrown.
 838      * If no exception is thrown, the specified property is set to the given
 839      * value.
 840      *
 841      * @param      key   the name of the system property.
 842      * @param      value the value of the system property.
 843      * @return     the previous value of the system property,
 844      *             or <code>null</code> if it did not have one.
 845      *
 846      * @exception  SecurityException  if a security manager exists and its
 847      *             <code>checkPermission</code> method doesn't allow
 848      *             setting of the specified property.
 849      * @exception  NullPointerException if <code>key</code> or
 850      *             <code>value</code> is <code>null</code>.
 851      * @exception  IllegalArgumentException if <code>key</code> is empty.
 852      * @see        #getProperty
 853      * @see        java.lang.System#getProperty(java.lang.String)
 854      * @see        java.lang.System#getProperty(java.lang.String, java.lang.String)
 855      * @see        java.util.PropertyPermission
 856      * @see        SecurityManager#checkPermission
 857      * @since      1.2
 858      */
 859     public static String setProperty(String key, String value) {
 860         checkKey(key);
 861         SecurityManager sm = getSecurityManager();
 862         if (sm != null) {
 863             sm.checkPermission(new PropertyPermission(key,
 864                 SecurityConstants.PROPERTY_WRITE_ACTION));
 865         }
 866 
 867         return (String) props.setProperty(key, value);
 868     }
 869 
 870     /**
 871      * Removes the system property indicated by the specified key.
 872      * <p>
 873      * First, if a security manager exists, its
 874      * <code>SecurityManager.checkPermission</code> method
 875      * is called with a <code>PropertyPermission(key, "write")</code>
 876      * permission. This may result in a SecurityException being thrown.
 877      * If no exception is thrown, the specified property is removed.
 878      *
 879      * @param      key   the name of the system property to be removed.
 880      * @return     the previous string value of the system property,
 881      *             or <code>null</code> if there was no property with that key.
 882      *
 883      * @exception  SecurityException  if a security manager exists and its
 884      *             <code>checkPropertyAccess</code> method doesn't allow
 885      *              access to the specified system property.
 886      * @exception  NullPointerException if <code>key</code> is
 887      *             <code>null</code>.
 888      * @exception  IllegalArgumentException if <code>key</code> is empty.
 889      * @see        #getProperty
 890      * @see        #setProperty
 891      * @see        java.util.Properties
 892      * @see        java.lang.SecurityException
 893      * @see        java.lang.SecurityManager#checkPropertiesAccess()
 894      * @since 1.5
 895      */
 896     public static String clearProperty(String key) {
 897         checkKey(key);
 898         SecurityManager sm = getSecurityManager();
 899         if (sm != null) {
 900             sm.checkPermission(new PropertyPermission(key, "write"));
 901         }
 902 
 903         return (String) props.remove(key);
 904     }
 905 
 906     private static void checkKey(String key) {
 907         if (key == null) {
 908             throw new NullPointerException("key can't be null");
 909         }
 910         if (key.equals("")) {
 911             throw new IllegalArgumentException("key can't be empty");
 912         }
 913     }
 914 
 915     /**
 916      * Gets the value of the specified environment variable. An
 917      * environment variable is a system-dependent external named
 918      * value.
 919      *
 920      * <p>If a security manager exists, its
 921      * {@link SecurityManager#checkPermission checkPermission}
 922      * method is called with a
 923      * <code>{@link RuntimePermission}("getenv."+name)</code>
 924      * permission.  This may result in a {@link SecurityException}
 925      * being thrown.  If no exception is thrown the value of the
 926      * variable <code>name</code> is returned.
 927      *
 928      * <p><a id="EnvironmentVSSystemProperties"><i>System
 929      * properties</i> and <i>environment variables</i></a> are both
 930      * conceptually mappings between names and values.  Both
 931      * mechanisms can be used to pass user-defined information to a
 932      * Java process.  Environment variables have a more global effect,
 933      * because they are visible to all descendants of the process
 934      * which defines them, not just the immediate Java subprocess.
 935      * They can have subtly different semantics, such as case
 936      * insensitivity, on different operating systems.  For these
 937      * reasons, environment variables are more likely to have
 938      * unintended side effects.  It is best to use system properties
 939      * where possible.  Environment variables should be used when a
 940      * global effect is desired, or when an external system interface
 941      * requires an environment variable (such as <code>PATH</code>).
 942      *
 943      * <p>On UNIX systems the alphabetic case of <code>name</code> is
 944      * typically significant, while on Microsoft Windows systems it is
 945      * typically not.  For example, the expression
 946      * <code>System.getenv("FOO").equals(System.getenv("foo"))</code>
 947      * is likely to be true on Microsoft Windows.
 948      *
 949      * @param  name the name of the environment variable
 950      * @return the string value of the variable, or <code>null</code>
 951      *         if the variable is not defined in the system environment
 952      * @throws NullPointerException if <code>name</code> is <code>null</code>
 953      * @throws SecurityException
 954      *         if a security manager exists and its
 955      *         {@link SecurityManager#checkPermission checkPermission}
 956      *         method doesn't allow access to the environment variable
 957      *         <code>name</code>
 958      * @see    #getenv()
 959      * @see    ProcessBuilder#environment()
 960      */
 961     public static String getenv(String name) {
 962         SecurityManager sm = getSecurityManager();
 963         if (sm != null) {
 964             sm.checkPermission(new RuntimePermission("getenv."+name));
 965         }
 966 
 967         return ProcessEnvironment.getenv(name);
 968     }
 969 
 970 
 971     /**
 972      * Returns an unmodifiable string map view of the current system environment.
 973      * The environment is a system-dependent mapping from names to
 974      * values which is passed from parent to child processes.
 975      *
 976      * <p>If the system does not support environment variables, an
 977      * empty map is returned.
 978      *
 979      * <p>The returned map will never contain null keys or values.
 980      * Attempting to query the presence of a null key or value will
 981      * throw a {@link NullPointerException}.  Attempting to query
 982      * the presence of a key or value which is not of type
 983      * {@link String} will throw a {@link ClassCastException}.
 984      *
 985      * <p>The returned map and its collection views may not obey the
 986      * general contract of the {@link Object#equals} and
 987      * {@link Object#hashCode} methods.
 988      *
 989      * <p>The returned map is typically case-sensitive on all platforms.
 990      *
 991      * <p>If a security manager exists, its
 992      * {@link SecurityManager#checkPermission checkPermission}
 993      * method is called with a
 994      * <code>{@link RuntimePermission}("getenv.*")</code>
 995      * permission.  This may result in a {@link SecurityException} being
 996      * thrown.
 997      *
 998      * <p>When passing information to a Java subprocess,
 999      * <a href=#EnvironmentVSSystemProperties>system properties</a>
1000      * are generally preferred over environment variables.
1001      *
1002      * @return the environment as a map of variable names to values
1003      * @throws SecurityException
1004      *         if a security manager exists and its
1005      *         {@link SecurityManager#checkPermission checkPermission}
1006      *         method doesn't allow access to the process environment
1007      * @see    #getenv(String)
1008      * @see    ProcessBuilder#environment()
1009      * @since  1.5
1010      */
1011     public static java.util.Map<String,String> getenv() {
1012         SecurityManager sm = getSecurityManager();
1013         if (sm != null) {
1014             sm.checkPermission(new RuntimePermission("getenv.*"));
1015         }
1016 
1017         return ProcessEnvironment.getenv();
1018     }
1019 
1020     /**
1021      * {@code System.Logger} instances log messages that will be
1022      * routed to the underlying logging framework the {@link System.LoggerFinder
1023      * LoggerFinder} uses.
1024      * <p>
1025      * {@code System.Logger} instances are typically obtained from
1026      * the {@link java.lang.System System} class, by calling
1027      * {@link java.lang.System#getLogger(java.lang.String) System.getLogger(loggerName)}
1028      * or {@link java.lang.System#getLogger(java.lang.String, java.util.ResourceBundle)
1029      * System.getLogger(loggerName, bundle)}.
1030      *
1031      * @see java.lang.System#getLogger(java.lang.String)
1032      * @see java.lang.System#getLogger(java.lang.String, java.util.ResourceBundle)
1033      * @see java.lang.System.LoggerFinder
1034      *
1035      * @since 9
1036      *
1037      */
1038     public interface Logger {
1039 
1040         /**
1041          * System {@linkplain Logger loggers} levels.
1042          * <p>
1043          * A level has a {@linkplain #getName() name} and {@linkplain
1044          * #getSeverity() severity}.
1045          * Level values are {@link #ALL}, {@link #TRACE}, {@link #DEBUG},
1046          * {@link #INFO}, {@link #WARNING}, {@link #ERROR}, {@link #OFF},
1047          * by order of increasing severity.
1048          * <br>
1049          * {@link #ALL} and {@link #OFF}
1050          * are simple markers with severities mapped respectively to
1051          * {@link java.lang.Integer#MIN_VALUE Integer.MIN_VALUE} and
1052          * {@link java.lang.Integer#MAX_VALUE Integer.MAX_VALUE}.
1053          * <p>
1054          * <b>Severity values and Mapping to {@code java.util.logging.Level}.</b>
1055          * <p>
1056          * {@linkplain System.Logger.Level System logger levels} are mapped to
1057          * {@linkplain java.util.logging.Level  java.util.logging levels}
1058          * of corresponding severity.
1059          * <br>The mapping is as follows:
1060          * <br><br>
1061          * <table class="striped">
1062          * <caption>System.Logger Severity Level Mapping</caption>
1063          * <thead>
1064          * <tr><th scope="col">System.Logger Levels</th>
1065          *     <th scope="col">java.util.logging Levels</th>
1066          * </thead>
1067          * <tbody>
1068          * <tr><th scope="row">{@link Logger.Level#ALL ALL}</th>
1069          *     <td>{@link java.util.logging.Level#ALL ALL}</td>
1070          * <tr><th scope="row">{@link Logger.Level#TRACE TRACE}</th>
1071          *     <td>{@link java.util.logging.Level#FINER FINER}</td>
1072          * <tr><th scope="row">{@link Logger.Level#DEBUG DEBUG}</th>
1073          *     <td>{@link java.util.logging.Level#FINE FINE}</td>
1074          * <tr><th scope="row">{@link Logger.Level#INFO INFO}</th>
1075          *     <td>{@link java.util.logging.Level#INFO INFO}</td>
1076          * <tr><th scope="row">{@link Logger.Level#WARNING WARNING}</th>
1077          *     <td>{@link java.util.logging.Level#WARNING WARNING}</td>
1078          * <tr><th scope="row">{@link Logger.Level#ERROR ERROR}</th>
1079          *     <td>{@link java.util.logging.Level#SEVERE SEVERE}</td>
1080          * <tr><th scope="row">{@link Logger.Level#OFF OFF}</th>
1081          *     <td>{@link java.util.logging.Level#OFF OFF}</td>
1082          * </tbody>
1083          * </table>
1084          *
1085          * @since 9
1086          *
1087          * @see java.lang.System.LoggerFinder
1088          * @see java.lang.System.Logger
1089          */
1090         public enum Level {
1091 
1092             // for convenience, we're reusing java.util.logging.Level int values
1093             // the mapping logic in sun.util.logging.PlatformLogger depends
1094             // on this.
1095             /**
1096              * A marker to indicate that all levels are enabled.
1097              * This level {@linkplain #getSeverity() severity} is
1098              * {@link Integer#MIN_VALUE}.
1099              */
1100             ALL(Integer.MIN_VALUE),  // typically mapped to/from j.u.l.Level.ALL
1101             /**
1102              * {@code TRACE} level: usually used to log diagnostic information.
1103              * This level {@linkplain #getSeverity() severity} is
1104              * {@code 400}.
1105              */
1106             TRACE(400),   // typically mapped to/from j.u.l.Level.FINER
1107             /**
1108              * {@code DEBUG} level: usually used to log debug information traces.
1109              * This level {@linkplain #getSeverity() severity} is
1110              * {@code 500}.
1111              */
1112             DEBUG(500),   // typically mapped to/from j.u.l.Level.FINEST/FINE/CONFIG
1113             /**
1114              * {@code INFO} level: usually used to log information messages.
1115              * This level {@linkplain #getSeverity() severity} is
1116              * {@code 800}.
1117              */
1118             INFO(800),    // typically mapped to/from j.u.l.Level.INFO
1119             /**
1120              * {@code WARNING} level: usually used to log warning messages.
1121              * This level {@linkplain #getSeverity() severity} is
1122              * {@code 900}.
1123              */
1124             WARNING(900), // typically mapped to/from j.u.l.Level.WARNING
1125             /**
1126              * {@code ERROR} level: usually used to log error messages.
1127              * This level {@linkplain #getSeverity() severity} is
1128              * {@code 1000}.
1129              */
1130             ERROR(1000),  // typically mapped to/from j.u.l.Level.SEVERE
1131             /**
1132              * A marker to indicate that all levels are disabled.
1133              * This level {@linkplain #getSeverity() severity} is
1134              * {@link Integer#MAX_VALUE}.
1135              */
1136             OFF(Integer.MAX_VALUE);  // typically mapped to/from j.u.l.Level.OFF
1137 
1138             private final int severity;
1139 
1140             private Level(int severity) {
1141                 this.severity = severity;
1142             }
1143 
1144             /**
1145              * Returns the name of this level.
1146              * @return this level {@linkplain #name()}.
1147              */
1148             public final String getName() {
1149                 return name();
1150             }
1151 
1152             /**
1153              * Returns the severity of this level.
1154              * A higher severity means a more severe condition.
1155              * @return this level severity.
1156              */
1157             public final int getSeverity() {
1158                 return severity;
1159             }
1160         }
1161 
1162         /**
1163          * Returns the name of this logger.
1164          *
1165          * @return the logger name.
1166          */
1167         public String getName();
1168 
1169         /**
1170          * Checks if a message of the given level would be logged by
1171          * this logger.
1172          *
1173          * @param level the log message level.
1174          * @return {@code true} if the given log message level is currently
1175          *         being logged.
1176          *
1177          * @throws NullPointerException if {@code level} is {@code null}.
1178          */
1179         public boolean isLoggable(Level level);
1180 
1181         /**
1182          * Logs a message.
1183          *
1184          * @implSpec The default implementation for this method calls
1185          * {@code this.log(level, (ResourceBundle)null, msg, (Object[])null);}
1186          *
1187          * @param level the log message level.
1188          * @param msg the string message (or a key in the message catalog, if
1189          * this logger is a {@link
1190          * LoggerFinder#getLocalizedLogger(java.lang.String,
1191          * java.util.ResourceBundle, java.lang.Module) localized logger});
1192          * can be {@code null}.
1193          *
1194          * @throws NullPointerException if {@code level} is {@code null}.
1195          */
1196         public default void log(Level level, String msg) {
1197             log(level, (ResourceBundle) null, msg, (Object[]) null);
1198         }
1199 
1200         /**
1201          * Logs a lazily supplied message.
1202          * <p>
1203          * If the logger is currently enabled for the given log message level
1204          * then a message is logged that is the result produced by the
1205          * given supplier function.  Otherwise, the supplier is not operated on.
1206          *
1207          * @implSpec When logging is enabled for the given level, the default
1208          * implementation for this method calls
1209          * {@code this.log(level, (ResourceBundle)null, msgSupplier.get(), (Object[])null);}
1210          *
1211          * @param level the log message level.
1212          * @param msgSupplier a supplier function that produces a message.
1213          *
1214          * @throws NullPointerException if {@code level} is {@code null},
1215          *         or {@code msgSupplier} is {@code null}.
1216          */
1217         public default void log(Level level, Supplier<String> msgSupplier) {
1218             Objects.requireNonNull(msgSupplier);
1219             if (isLoggable(Objects.requireNonNull(level))) {
1220                 log(level, (ResourceBundle) null, msgSupplier.get(), (Object[]) null);
1221             }
1222         }
1223 
1224         /**
1225          * Logs a message produced from the given object.
1226          * <p>
1227          * If the logger is currently enabled for the given log message level then
1228          * a message is logged that, by default, is the result produced from
1229          * calling  toString on the given object.
1230          * Otherwise, the object is not operated on.
1231          *
1232          * @implSpec When logging is enabled for the given level, the default
1233          * implementation for this method calls
1234          * {@code this.log(level, (ResourceBundle)null, obj.toString(), (Object[])null);}
1235          *
1236          * @param level the log message level.
1237          * @param obj the object to log.
1238          *
1239          * @throws NullPointerException if {@code level} is {@code null}, or
1240          *         {@code obj} is {@code null}.
1241          */
1242         public default void log(Level level, Object obj) {
1243             Objects.requireNonNull(obj);
1244             if (isLoggable(Objects.requireNonNull(level))) {
1245                 this.log(level, (ResourceBundle) null, obj.toString(), (Object[]) null);
1246             }
1247         }
1248 
1249         /**
1250          * Logs a message associated with a given throwable.
1251          *
1252          * @implSpec The default implementation for this method calls
1253          * {@code this.log(level, (ResourceBundle)null, msg, thrown);}
1254          *
1255          * @param level the log message level.
1256          * @param msg the string message (or a key in the message catalog, if
1257          * this logger is a {@link
1258          * LoggerFinder#getLocalizedLogger(java.lang.String,
1259          * java.util.ResourceBundle, java.lang.Module) localized logger});
1260          * can be {@code null}.
1261          * @param thrown a {@code Throwable} associated with the log message;
1262          *        can be {@code null}.
1263          *
1264          * @throws NullPointerException if {@code level} is {@code null}.
1265          */
1266         public default void log(Level level, String msg, Throwable thrown) {
1267             this.log(level, null, msg, thrown);
1268         }
1269 
1270         /**
1271          * Logs a lazily supplied message associated with a given throwable.
1272          * <p>
1273          * If the logger is currently enabled for the given log message level
1274          * then a message is logged that is the result produced by the
1275          * given supplier function.  Otherwise, the supplier is not operated on.
1276          *
1277          * @implSpec When logging is enabled for the given level, the default
1278          * implementation for this method calls
1279          * {@code this.log(level, (ResourceBundle)null, msgSupplier.get(), thrown);}
1280          *
1281          * @param level one of the log message level identifiers.
1282          * @param msgSupplier a supplier function that produces a message.
1283          * @param thrown a {@code Throwable} associated with log message;
1284          *               can be {@code null}.
1285          *
1286          * @throws NullPointerException if {@code level} is {@code null}, or
1287          *                               {@code msgSupplier} is {@code null}.
1288          */
1289         public default void log(Level level, Supplier<String> msgSupplier,
1290                 Throwable thrown) {
1291             Objects.requireNonNull(msgSupplier);
1292             if (isLoggable(Objects.requireNonNull(level))) {
1293                 this.log(level, null, msgSupplier.get(), thrown);
1294             }
1295         }
1296 
1297         /**
1298          * Logs a message with an optional list of parameters.
1299          *
1300          * @implSpec The default implementation for this method calls
1301          * {@code this.log(level, (ResourceBundle)null, format, params);}
1302          *
1303          * @param level one of the log message level identifiers.
1304          * @param format the string message format in {@link
1305          * java.text.MessageFormat} format, (or a key in the message
1306          * catalog, if this logger is a {@link
1307          * LoggerFinder#getLocalizedLogger(java.lang.String,
1308          * java.util.ResourceBundle, java.lang.Module) localized logger});
1309          * can be {@code null}.
1310          * @param params an optional list of parameters to the message (may be
1311          * none).
1312          *
1313          * @throws NullPointerException if {@code level} is {@code null}.
1314          */
1315         public default void log(Level level, String format, Object... params) {
1316             this.log(level, null, format, params);
1317         }
1318 
1319         /**
1320          * Logs a localized message associated with a given throwable.
1321          * <p>
1322          * If the given resource bundle is non-{@code null},  the {@code msg}
1323          * string is localized using the given resource bundle.
1324          * Otherwise the {@code msg} string is not localized.
1325          *
1326          * @param level the log message level.
1327          * @param bundle a resource bundle to localize {@code msg}; can be
1328          * {@code null}.
1329          * @param msg the string message (or a key in the message catalog,
1330          *            if {@code bundle} is not {@code null}); can be {@code null}.
1331          * @param thrown a {@code Throwable} associated with the log message;
1332          *        can be {@code null}.
1333          *
1334          * @throws NullPointerException if {@code level} is {@code null}.
1335          */
1336         public void log(Level level, ResourceBundle bundle, String msg,
1337                 Throwable thrown);
1338 
1339         /**
1340          * Logs a message with resource bundle and an optional list of
1341          * parameters.
1342          * <p>
1343          * If the given resource bundle is non-{@code null},  the {@code format}
1344          * string is localized using the given resource bundle.
1345          * Otherwise the {@code format} string is not localized.
1346          *
1347          * @param level the log message level.
1348          * @param bundle a resource bundle to localize {@code format}; can be
1349          * {@code null}.
1350          * @param format the string message format in {@link
1351          * java.text.MessageFormat} format, (or a key in the message
1352          * catalog if {@code bundle} is not {@code null}); can be {@code null}.
1353          * @param params an optional list of parameters to the message (may be
1354          * none).
1355          *
1356          * @throws NullPointerException if {@code level} is {@code null}.
1357          */
1358         public void log(Level level, ResourceBundle bundle, String format,
1359                 Object... params);
1360 
1361 
1362     }
1363 
1364     /**
1365      * The {@code LoggerFinder} service is responsible for creating, managing,
1366      * and configuring loggers to the underlying framework it uses.
1367      * <p>
1368      * A logger finder is a concrete implementation of this class that has a
1369      * zero-argument constructor and implements the abstract methods defined
1370      * by this class.
1371      * The loggers returned from a logger finder are capable of routing log
1372      * messages to the logging backend this provider supports.
1373      * A given invocation of the Java Runtime maintains a single
1374      * system-wide LoggerFinder instance that is loaded as follows:
1375      * <ul>
1376      *    <li>First it finds any custom {@code LoggerFinder} provider
1377      *        using the {@link java.util.ServiceLoader} facility with the
1378      *        {@linkplain ClassLoader#getSystemClassLoader() system class
1379      *        loader}.</li>
1380      *    <li>If no {@code LoggerFinder} provider is found, the system default
1381      *        {@code LoggerFinder} implementation will be used.</li>
1382      * </ul>
1383      * <p>
1384      * An application can replace the logging backend
1385      * <i>even when the java.logging module is present</i>, by simply providing
1386      * and declaring an implementation of the {@link LoggerFinder} service.
1387      * <p>
1388      * <b>Default Implementation</b>
1389      * <p>
1390      * The system default {@code LoggerFinder} implementation uses
1391      * {@code java.util.logging} as the backend framework when the
1392      * {@code java.logging} module is present.
1393      * It returns a {@linkplain System.Logger logger} instance
1394      * that will route log messages to a {@link java.util.logging.Logger
1395      * java.util.logging.Logger}. Otherwise, if {@code java.logging} is not
1396      * present, the default implementation will return a simple logger
1397      * instance that will route log messages of {@code INFO} level and above to
1398      * the console ({@code System.err}).
1399      * <p>
1400      * <b>Logging Configuration</b>
1401      * <p>
1402      * {@linkplain Logger Logger} instances obtained from the
1403      * {@code LoggerFinder} factory methods are not directly configurable by
1404      * the application. Configuration is the responsibility of the underlying
1405      * logging backend, and usually requires using APIs specific to that backend.
1406      * <p>For the default {@code LoggerFinder} implementation
1407      * using {@code java.util.logging} as its backend, refer to
1408      * {@link java.util.logging java.util.logging} for logging configuration.
1409      * For the default {@code LoggerFinder} implementation returning simple loggers
1410      * when the {@code java.logging} module is absent, the configuration
1411      * is implementation dependent.
1412      * <p>
1413      * Usually an application that uses a logging framework will log messages
1414      * through a logger facade defined (or supported) by that framework.
1415      * Applications that wish to use an external framework should log
1416      * through the facade associated with that framework.
1417      * <p>
1418      * A system class that needs to log messages will typically obtain
1419      * a {@link System.Logger} instance to route messages to the logging
1420      * framework selected by the application.
1421      * <p>
1422      * Libraries and classes that only need loggers to produce log messages
1423      * should not attempt to configure loggers by themselves, as that
1424      * would make them dependent from a specific implementation of the
1425      * {@code LoggerFinder} service.
1426      * <p>
1427      * In addition, when a security manager is present, loggers provided to
1428      * system classes should not be directly configurable through the logging
1429      * backend without requiring permissions.
1430      * <br>
1431      * It is the responsibility of the provider of
1432      * the concrete {@code LoggerFinder} implementation to ensure that
1433      * these loggers are not configured by untrusted code without proper
1434      * permission checks, as configuration performed on such loggers usually
1435      * affects all applications in the same Java Runtime.
1436      * <p>
1437      * <b>Message Levels and Mapping to backend levels</b>
1438      * <p>
1439      * A logger finder is responsible for mapping from a {@code
1440      * System.Logger.Level} to a level supported by the logging backend it uses.
1441      * <br>The default LoggerFinder using {@code java.util.logging} as the backend
1442      * maps {@code System.Logger} levels to
1443      * {@linkplain java.util.logging.Level java.util.logging} levels
1444      * of corresponding severity - as described in {@link Logger.Level
1445      * Logger.Level}.
1446      *
1447      * @see java.lang.System
1448      * @see java.lang.System.Logger
1449      *
1450      * @since 9
1451      */
1452     public static abstract class LoggerFinder {
1453         /**
1454          * The {@code RuntimePermission("loggerFinder")} is
1455          * necessary to subclass and instantiate the {@code LoggerFinder} class,
1456          * as well as to obtain loggers from an instance of that class.
1457          */
1458         static final RuntimePermission LOGGERFINDER_PERMISSION =
1459                 new RuntimePermission("loggerFinder");
1460 
1461         /**
1462          * Creates a new instance of {@code LoggerFinder}.
1463          *
1464          * @implNote It is recommended that a {@code LoggerFinder} service
1465          *   implementation does not perform any heavy initialization in its
1466          *   constructor, in order to avoid possible risks of deadlock or class
1467          *   loading cycles during the instantiation of the service provider.
1468          *
1469          * @throws SecurityException if a security manager is present and its
1470          *         {@code checkPermission} method doesn't allow the
1471          *         {@code RuntimePermission("loggerFinder")}.
1472          */
1473         protected LoggerFinder() {
1474             this(checkPermission());
1475         }
1476 
1477         private LoggerFinder(Void unused) {
1478             // nothing to do.
1479         }
1480 
1481         private static Void checkPermission() {
1482             final SecurityManager sm = System.getSecurityManager();
1483             if (sm != null) {
1484                 sm.checkPermission(LOGGERFINDER_PERMISSION);
1485             }
1486             return null;
1487         }
1488 
1489         /**
1490          * Returns an instance of {@link Logger Logger}
1491          * for the given {@code module}.
1492          *
1493          * @param name the name of the logger.
1494          * @param module the module for which the logger is being requested.
1495          *
1496          * @return a {@link Logger logger} suitable for use within the given
1497          *         module.
1498          * @throws NullPointerException if {@code name} is {@code null} or
1499          *        {@code module} is {@code null}.
1500          * @throws SecurityException if a security manager is present and its
1501          *         {@code checkPermission} method doesn't allow the
1502          *         {@code RuntimePermission("loggerFinder")}.
1503          */
1504         public abstract Logger getLogger(String name, Module module);
1505 
1506         /**
1507          * Returns a localizable instance of {@link Logger Logger}
1508          * for the given {@code module}.
1509          * The returned logger will use the provided resource bundle for
1510          * message localization.
1511          *
1512          * @implSpec By default, this method calls {@link
1513          * #getLogger(java.lang.String, java.lang.Module)
1514          * this.getLogger(name, module)} to obtain a logger, then wraps that
1515          * logger in a {@link Logger} instance where all methods that do not
1516          * take a {@link ResourceBundle} as parameter are redirected to one
1517          * which does - passing the given {@code bundle} for
1518          * localization. So for instance, a call to {@link
1519          * Logger#log(Level, String) Logger.log(Level.INFO, msg)}
1520          * will end up as a call to {@link
1521          * Logger#log(Level, ResourceBundle, String, Object...)
1522          * Logger.log(Level.INFO, bundle, msg, (Object[])null)} on the wrapped
1523          * logger instance.
1524          * Note however that by default, string messages returned by {@link
1525          * java.util.function.Supplier Supplier&lt;String&gt;} will not be
1526          * localized, as it is assumed that such strings are messages which are
1527          * already constructed, rather than keys in a resource bundle.
1528          * <p>
1529          * An implementation of {@code LoggerFinder} may override this method,
1530          * for example, when the underlying logging backend provides its own
1531          * mechanism for localizing log messages, then such a
1532          * {@code LoggerFinder} would be free to return a logger
1533          * that makes direct use of the mechanism provided by the backend.
1534          *
1535          * @param name    the name of the logger.
1536          * @param bundle  a resource bundle; can be {@code null}.
1537          * @param module  the module for which the logger is being requested.
1538          * @return an instance of {@link Logger Logger}  which will use the
1539          * provided resource bundle for message localization.
1540          *
1541          * @throws NullPointerException if {@code name} is {@code null} or
1542          *         {@code module} is {@code null}.
1543          * @throws SecurityException if a security manager is present and its
1544          *         {@code checkPermission} method doesn't allow the
1545          *         {@code RuntimePermission("loggerFinder")}.
1546          */
1547         public Logger getLocalizedLogger(String name, ResourceBundle bundle,
1548                                          Module module) {
1549             return new LocalizedLoggerWrapper<>(getLogger(name, module), bundle);
1550         }
1551 
1552         /**
1553          * Returns the {@code LoggerFinder} instance. There is one
1554          * single system-wide {@code LoggerFinder} instance in
1555          * the Java Runtime.  See the class specification of how the
1556          * {@link LoggerFinder LoggerFinder} implementation is located and
1557          * loaded.
1558 
1559          * @return the {@link LoggerFinder LoggerFinder} instance.
1560          * @throws SecurityException if a security manager is present and its
1561          *         {@code checkPermission} method doesn't allow the
1562          *         {@code RuntimePermission("loggerFinder")}.
1563          */
1564         public static LoggerFinder getLoggerFinder() {
1565             final SecurityManager sm = System.getSecurityManager();
1566             if (sm != null) {
1567                 sm.checkPermission(LOGGERFINDER_PERMISSION);
1568             }
1569             return accessProvider();
1570         }
1571 
1572 
1573         private static volatile LoggerFinder service;
1574         static LoggerFinder accessProvider() {
1575             // We do not need to synchronize: LoggerFinderLoader will
1576             // always return the same instance, so if we don't have it,
1577             // just fetch it again.
1578             if (service == null) {
1579                 PrivilegedAction<LoggerFinder> pa =
1580                         () -> LoggerFinderLoader.getLoggerFinder();
1581                 service = AccessController.doPrivileged(pa, null,
1582                         LOGGERFINDER_PERMISSION);
1583             }
1584             return service;
1585         }
1586 
1587     }
1588 
1589 
1590     /**
1591      * Returns an instance of {@link Logger Logger} for the caller's
1592      * use.
1593      *
1594      * @implSpec
1595      * Instances returned by this method route messages to loggers
1596      * obtained by calling {@link LoggerFinder#getLogger(java.lang.String,
1597      * java.lang.Module) LoggerFinder.getLogger(name, module)}, where
1598      * {@code module} is the caller's module.
1599      * In cases where {@code System.getLogger} is called from a context where
1600      * there is no caller frame on the stack (e.g when called directly
1601      * from a JNI attached thread), {@code IllegalCallerException} is thrown.
1602      * To obtain a logger in such a context, use an auxiliary class that will
1603      * implicitly be identified as the caller, or use the system {@link
1604      * LoggerFinder#getLoggerFinder() LoggerFinder} to obtain a logger instead.
1605      * Note that doing the latter may eagerly initialize the underlying
1606      * logging system.
1607      *
1608      * @apiNote
1609      * This method may defer calling the {@link
1610      * LoggerFinder#getLogger(java.lang.String, java.lang.Module)
1611      * LoggerFinder.getLogger} method to create an actual logger supplied by
1612      * the logging backend, for instance, to allow loggers to be obtained during
1613      * the system initialization time.
1614      *
1615      * @param name the name of the logger.
1616      * @return an instance of {@link Logger} that can be used by the calling
1617      *         class.
1618      * @throws NullPointerException if {@code name} is {@code null}.
1619      * @throws IllegalCallerException if there is no Java caller frame on the
1620      *         stack.
1621      *
1622      * @since 9
1623      */
1624     @CallerSensitive
1625     public static Logger getLogger(String name) {
1626         Objects.requireNonNull(name);
1627         final Class<?> caller = Reflection.getCallerClass();
1628         if (caller == null) {
1629             throw new IllegalCallerException("no caller frame");
1630         }
1631         return LazyLoggers.getLogger(name, caller.getModule());
1632     }
1633 
1634     /**
1635      * Returns a localizable instance of {@link Logger
1636      * Logger} for the caller's use.
1637      * The returned logger will use the provided resource bundle for message
1638      * localization.
1639      *
1640      * @implSpec
1641      * The returned logger will perform message localization as specified
1642      * by {@link LoggerFinder#getLocalizedLogger(java.lang.String,
1643      * java.util.ResourceBundle, java.lang.Module)
1644      * LoggerFinder.getLocalizedLogger(name, bundle, module)}, where
1645      * {@code module} is the caller's module.
1646      * In cases where {@code System.getLogger} is called from a context where
1647      * there is no caller frame on the stack (e.g when called directly
1648      * from a JNI attached thread), {@code IllegalCallerException} is thrown.
1649      * To obtain a logger in such a context, use an auxiliary class that
1650      * will implicitly be identified as the caller, or use the system {@link
1651      * LoggerFinder#getLoggerFinder() LoggerFinder} to obtain a logger instead.
1652      * Note that doing the latter may eagerly initialize the underlying
1653      * logging system.
1654      *
1655      * @apiNote
1656      * This method is intended to be used after the system is fully initialized.
1657      * This method may trigger the immediate loading and initialization
1658      * of the {@link LoggerFinder} service, which may cause issues if the
1659      * Java Runtime is not ready to initialize the concrete service
1660      * implementation yet.
1661      * System classes which may be loaded early in the boot sequence and
1662      * need to log localized messages should create a logger using
1663      * {@link #getLogger(java.lang.String)} and then use the log methods that
1664      * take a resource bundle as parameter.
1665      *
1666      * @param name    the name of the logger.
1667      * @param bundle  a resource bundle.
1668      * @return an instance of {@link Logger} which will use the provided
1669      * resource bundle for message localization.
1670      * @throws NullPointerException if {@code name} is {@code null} or
1671      *         {@code bundle} is {@code null}.
1672      * @throws IllegalCallerException if there is no Java caller frame on the
1673      *         stack.
1674      *
1675      * @since 9
1676      */
1677     @CallerSensitive
1678     public static Logger getLogger(String name, ResourceBundle bundle) {
1679         final ResourceBundle rb = Objects.requireNonNull(bundle);
1680         Objects.requireNonNull(name);
1681         final Class<?> caller = Reflection.getCallerClass();
1682         if (caller == null) {
1683             throw new IllegalCallerException("no caller frame");
1684         }
1685         final SecurityManager sm = System.getSecurityManager();
1686         // We don't use LazyLoggers if a resource bundle is specified.
1687         // Bootstrap sensitive classes in the JDK do not use resource bundles
1688         // when logging. This could be revisited later, if it needs to.
1689         if (sm != null) {
1690             final PrivilegedAction<Logger> pa =
1691                     () -> LoggerFinder.accessProvider()
1692                             .getLocalizedLogger(name, rb, caller.getModule());
1693             return AccessController.doPrivileged(pa, null,
1694                                          LoggerFinder.LOGGERFINDER_PERMISSION);
1695         }
1696         return LoggerFinder.accessProvider()
1697                 .getLocalizedLogger(name, rb, caller.getModule());
1698     }
1699 
1700     /**
1701      * Terminates the currently running Java Virtual Machine. The
1702      * argument serves as a status code; by convention, a nonzero status
1703      * code indicates abnormal termination.
1704      * <p>
1705      * This method calls the <code>exit</code> method in class
1706      * <code>Runtime</code>. This method never returns normally.
1707      * <p>
1708      * The call <code>System.exit(n)</code> is effectively equivalent to
1709      * the call:
1710      * <blockquote><pre>
1711      * Runtime.getRuntime().exit(n)
1712      * </pre></blockquote>
1713      *
1714      * @param      status   exit status.
1715      * @throws  SecurityException
1716      *        if a security manager exists and its <code>checkExit</code>
1717      *        method doesn't allow exit with the specified status.
1718      * @see        java.lang.Runtime#exit(int)
1719      */
1720     public static void exit(int status) {
1721         Runtime.getRuntime().exit(status);
1722     }
1723 
1724     /**
1725      * Runs the garbage collector.
1726      * <p>
1727      * Calling the <code>gc</code> method suggests that the Java Virtual
1728      * Machine expend effort toward recycling unused objects in order to
1729      * make the memory they currently occupy available for quick reuse.
1730      * When control returns from the method call, the Java Virtual
1731      * Machine has made a best effort to reclaim space from all discarded
1732      * objects.
1733      * <p>
1734      * The call <code>System.gc()</code> is effectively equivalent to the
1735      * call:
1736      * <blockquote><pre>
1737      * Runtime.getRuntime().gc()
1738      * </pre></blockquote>
1739      *
1740      * @see     java.lang.Runtime#gc()
1741      */
1742     public static void gc() {
1743         Runtime.getRuntime().gc();
1744     }
1745 
1746     /**
1747      * Runs the finalization methods of any objects pending finalization.
1748      * <p>
1749      * Calling this method suggests that the Java Virtual Machine expend
1750      * effort toward running the <code>finalize</code> methods of objects
1751      * that have been found to be discarded but whose <code>finalize</code>
1752      * methods have not yet been run. When control returns from the
1753      * method call, the Java Virtual Machine has made a best effort to
1754      * complete all outstanding finalizations.
1755      * <p>
1756      * The call <code>System.runFinalization()</code> is effectively
1757      * equivalent to the call:
1758      * <blockquote><pre>
1759      * Runtime.getRuntime().runFinalization()
1760      * </pre></blockquote>
1761      *
1762      * @see     java.lang.Runtime#runFinalization()
1763      */
1764     public static void runFinalization() {
1765         Runtime.getRuntime().runFinalization();
1766     }
1767 
1768     /**
1769      * Enable or disable finalization on exit; doing so specifies that the
1770      * finalizers of all objects that have finalizers that have not yet been
1771      * automatically invoked are to be run before the Java runtime exits.
1772      * By default, finalization on exit is disabled.
1773      *
1774      * <p>If there is a security manager,
1775      * its <code>checkExit</code> method is first called
1776      * with 0 as its argument to ensure the exit is allowed.
1777      * This could result in a SecurityException.
1778      *
1779      * @deprecated  This method is inherently unsafe.  It may result in
1780      *      finalizers being called on live objects while other threads are
1781      *      concurrently manipulating those objects, resulting in erratic
1782      *      behavior or deadlock.
1783      *      This method is subject to removal in a future version of Java SE.
1784      * @param value indicating enabling or disabling of finalization
1785      * @throws  SecurityException
1786      *        if a security manager exists and its <code>checkExit</code>
1787      *        method doesn't allow the exit.
1788      *
1789      * @see     java.lang.Runtime#exit(int)
1790      * @see     java.lang.Runtime#gc()
1791      * @see     java.lang.SecurityManager#checkExit(int)
1792      * @since   1.1
1793      */
1794     @Deprecated(since="1.2", forRemoval=true)
1795     @SuppressWarnings("removal")
1796     public static void runFinalizersOnExit(boolean value) {
1797         Runtime.runFinalizersOnExit(value);
1798     }
1799 
1800     /**
1801      * Loads the native library specified by the filename argument.  The filename
1802      * argument must be an absolute path name.
1803      *
1804      * If the filename argument, when stripped of any platform-specific library
1805      * prefix, path, and file extension, indicates a library whose name is,
1806      * for example, L, and a native library called L is statically linked
1807      * with the VM, then the JNI_OnLoad_L function exported by the library
1808      * is invoked rather than attempting to load a dynamic library.
1809      * A filename matching the argument does not have to exist in the
1810      * file system.
1811      * See the <a href="{@docRoot}/../specs/jni/index.html"> JNI Specification</a>
1812      * for more details.
1813      *
1814      * Otherwise, the filename argument is mapped to a native library image in
1815      * an implementation-dependent manner.
1816      *
1817      * <p>
1818      * The call <code>System.load(name)</code> is effectively equivalent
1819      * to the call:
1820      * <blockquote><pre>
1821      * Runtime.getRuntime().load(name)
1822      * </pre></blockquote>
1823      *
1824      * @param      filename   the file to load.
1825      * @exception  SecurityException  if a security manager exists and its
1826      *             <code>checkLink</code> method doesn't allow
1827      *             loading of the specified dynamic library
1828      * @exception  UnsatisfiedLinkError  if either the filename is not an
1829      *             absolute path name, the native library is not statically
1830      *             linked with the VM, or the library cannot be mapped to
1831      *             a native library image by the host system.
1832      * @exception  NullPointerException if <code>filename</code> is
1833      *             <code>null</code>
1834      * @see        java.lang.Runtime#load(java.lang.String)
1835      * @see        java.lang.SecurityManager#checkLink(java.lang.String)
1836      */
1837     @CallerSensitive
1838     public static void load(String filename) {
1839         Runtime.getRuntime().load0(Reflection.getCallerClass(), filename);
1840     }
1841 
1842     /**
1843      * Loads the native library specified by the <code>libname</code>
1844      * argument.  The <code>libname</code> argument must not contain any platform
1845      * specific prefix, file extension or path. If a native library
1846      * called <code>libname</code> is statically linked with the VM, then the
1847      * JNI_OnLoad_<code>libname</code> function exported by the library is invoked.
1848      * See the <a href="{@docRoot}/../specs/jni/index.html"> JNI Specification</a>
1849      * for more details.
1850      *
1851      * Otherwise, the libname argument is loaded from a system library
1852      * location and mapped to a native library image in an implementation-
1853      * dependent manner.
1854      * <p>
1855      * The call <code>System.loadLibrary(name)</code> is effectively
1856      * equivalent to the call
1857      * <blockquote><pre>
1858      * Runtime.getRuntime().loadLibrary(name)
1859      * </pre></blockquote>
1860      *
1861      * @param      libname   the name of the library.
1862      * @exception  SecurityException  if a security manager exists and its
1863      *             <code>checkLink</code> method doesn't allow
1864      *             loading of the specified dynamic library
1865      * @exception  UnsatisfiedLinkError if either the libname argument
1866      *             contains a file path, the native library is not statically
1867      *             linked with the VM,  or the library cannot be mapped to a
1868      *             native library image by the host system.
1869      * @exception  NullPointerException if <code>libname</code> is
1870      *             <code>null</code>
1871      * @see        java.lang.Runtime#loadLibrary(java.lang.String)
1872      * @see        java.lang.SecurityManager#checkLink(java.lang.String)
1873      */
1874     @CallerSensitive
1875     public static void loadLibrary(String libname) {
1876         Runtime.getRuntime().loadLibrary0(Reflection.getCallerClass(), libname);
1877     }
1878 
1879     /**
1880      * Maps a library name into a platform-specific string representing
1881      * a native library.
1882      *
1883      * @param      libname the name of the library.
1884      * @return     a platform-dependent native library name.
1885      * @exception  NullPointerException if <code>libname</code> is
1886      *             <code>null</code>
1887      * @see        java.lang.System#loadLibrary(java.lang.String)
1888      * @see        java.lang.ClassLoader#findLibrary(java.lang.String)
1889      * @since      1.2
1890      */
1891     public static native String mapLibraryName(String libname);
1892 
1893     /**
1894      * Create PrintStream for stdout/err based on encoding.
1895      */
1896     private static PrintStream newPrintStream(FileOutputStream fos, String enc) {
1897        if (enc != null) {
1898             try {
1899                 return new PrintStream(new BufferedOutputStream(fos, 128), true, enc);
1900             } catch (UnsupportedEncodingException uee) {}
1901         }
1902         return new PrintStream(new BufferedOutputStream(fos, 128), true);
1903     }
1904 
1905     /**
1906      * Logs an exception/error at initialization time to stdout or stderr.
1907      *
1908      * @param printToStderr to print to stderr rather than stdout
1909      * @param printStackTrace to print the stack trace
1910      * @param msg the message to print before the exception, can be {@code null}
1911      * @param e the exception or error
1912      */
1913     private static void logInitException(boolean printToStderr,
1914                                          boolean printStackTrace,
1915                                          String msg,
1916                                          Throwable e) {
1917         if (VM.initLevel() < 1) {
1918             throw new InternalError("system classes not initialized");
1919         }
1920         PrintStream log = (printToStderr) ? err : out;
1921         if (msg != null) {
1922             log.println(msg);
1923         }
1924         if (printStackTrace) {
1925             e.printStackTrace(log);
1926         } else {
1927             log.println(e);
1928             for (Throwable suppressed : e.getSuppressed()) {
1929                 log.println("Suppressed: " + suppressed);
1930             }
1931             Throwable cause = e.getCause();
1932             if (cause != null) {
1933                 log.println("Caused by: " + cause);
1934             }
1935         }
1936     }
1937 
1938     /**
1939      * Initialize the system class.  Called after thread initialization.
1940      */
1941     private static void initPhase1() {
1942 
1943         // VM might invoke JNU_NewStringPlatform() to set those encoding
1944         // sensitive properties (user.home, user.name, boot.class.path, etc.)
1945         // during "props" initialization, in which it may need access, via
1946         // System.getProperty(), to the related system encoding property that
1947         // have been initialized (put into "props") at early stage of the
1948         // initialization. So make sure the "props" is available at the
1949         // very beginning of the initialization and all system properties to
1950         // be put into it directly.
1951         props = new Properties(84);
1952         initProperties(props);  // initialized by the VM
1953 
1954         // There are certain system configurations that may be controlled by
1955         // VM options such as the maximum amount of direct memory and
1956         // Integer cache size used to support the object identity semantics
1957         // of autoboxing.  Typically, the library will obtain these values
1958         // from the properties set by the VM.  If the properties are for
1959         // internal implementation use only, these properties should be
1960         // removed from the system properties.
1961         //
1962         // See java.lang.Integer.IntegerCache and the
1963         // VM.saveAndRemoveProperties method for example.
1964         //
1965         // Save a private copy of the system properties object that
1966         // can only be accessed by the internal implementation.  Remove
1967         // certain system properties that are not intended for public access.
1968         VM.saveAndRemoveProperties(props);
1969 
1970         lineSeparator = props.getProperty("line.separator");
1971         VersionProps.init();
1972 
1973         FileInputStream fdIn = new FileInputStream(FileDescriptor.in);
1974         FileOutputStream fdOut = new FileOutputStream(FileDescriptor.out);
1975         FileOutputStream fdErr = new FileOutputStream(FileDescriptor.err);
1976         setIn0(new BufferedInputStream(fdIn));
1977         setOut0(newPrintStream(fdOut, props.getProperty("sun.stdout.encoding")));
1978         setErr0(newPrintStream(fdErr, props.getProperty("sun.stderr.encoding")));
1979 
1980         // Setup Java signal handlers for HUP, TERM, and INT (where available).
1981         Terminator.setup();
1982 
1983         // Initialize any miscellaneous operating system settings that need to be
1984         // set for the class libraries. Currently this is no-op everywhere except
1985         // for Windows where the process-wide error mode is set before the java.io
1986         // classes are used.
1987         VM.initializeOSEnvironment();
1988 
1989         // The main thread is not added to its thread group in the same
1990         // way as other threads; we must do it ourselves here.
1991         Thread current = Thread.currentThread();
1992         current.getThreadGroup().add(current);
1993 
1994         // register shared secrets
1995         setJavaLangAccess();
1996 
1997         // Subsystems that are invoked during initialization can invoke
1998         // VM.isBooted() in order to avoid doing things that should
1999         // wait until the VM is fully initialized. The initialization level
2000         // is incremented from 0 to 1 here to indicate the first phase of
2001         // initialization has completed.
2002         // IMPORTANT: Ensure that this remains the last initialization action!
2003         VM.initLevel(1);
2004     }
2005 
2006     // @see #initPhase2()
2007     static ModuleLayer bootLayer;
2008 
2009     /*
2010      * Invoked by VM.  Phase 2 module system initialization.
2011      * Only classes in java.base can be loaded in this phase.
2012      *
2013      * @param printToStderr print exceptions to stderr rather than stdout
2014      * @param printStackTrace print stack trace when exception occurs
2015      *
2016      * @return JNI_OK for success, JNI_ERR for failure
2017      */
2018     private static int initPhase2(boolean printToStderr, boolean printStackTrace) {
2019         try {
2020             bootLayer = ModuleBootstrap.boot();
2021         } catch (Exception | Error e) {
2022             logInitException(printToStderr, printStackTrace,
2023                              "Error occurred during initialization of boot layer", e);
2024             return -1; // JNI_ERR
2025         }
2026 
2027         // module system initialized
2028         VM.initLevel(2);
2029 
2030         return 0; // JNI_OK
2031     }
2032 
2033     /*
2034      * Invoked by VM.  Phase 3 is the final system initialization:
2035      * 1. set security manager
2036      * 2. set system class loader
2037      * 3. set TCCL
2038      *
2039      * This method must be called after the module system initialization.
2040      * The security manager and system class loader may be custom class from
2041      * the application classpath or modulepath.
2042      */
2043     private static void initPhase3() {
2044         // set security manager
2045         String cn = System.getProperty("java.security.manager");
2046         if (cn != null) {
2047             if (cn.isEmpty() || "default".equals(cn)) {
2048                 System.setSecurityManager(new SecurityManager());
2049             } else {
2050                 try {
2051                     Class<?> c = Class.forName(cn, false, ClassLoader.getBuiltinAppClassLoader());
2052                     Constructor<?> ctor = c.getConstructor();
2053                     // Must be a public subclass of SecurityManager with
2054                     // a public no-arg constructor
2055                     if (!SecurityManager.class.isAssignableFrom(c) ||
2056                             !Modifier.isPublic(c.getModifiers()) ||
2057                             !Modifier.isPublic(ctor.getModifiers())) {
2058                         throw new Error("Could not create SecurityManager: " + ctor.toString());
2059                     }
2060                     // custom security manager implementation may be in unnamed module
2061                     // or a named module but non-exported package
2062                     ctor.setAccessible(true);
2063                     SecurityManager sm = (SecurityManager) ctor.newInstance();
2064                     System.setSecurityManager(sm);
2065                 } catch (Exception e) {
2066                     throw new Error("Could not create SecurityManager", e);
2067                 }
2068             }
2069         }
2070 
2071         // initializing the system class loader
2072         VM.initLevel(3);
2073 
2074         // system class loader initialized
2075         ClassLoader scl = ClassLoader.initSystemClassLoader();
2076 
2077         // set TCCL
2078         Thread.currentThread().setContextClassLoader(scl);
2079 
2080         // system is fully initialized
2081         VM.initLevel(4);
2082     }
2083 
2084     private static void setJavaLangAccess() {
2085         // Allow privileged classes outside of java.lang
2086         SharedSecrets.setJavaLangAccess(new JavaLangAccess() {
2087             public List<Method> getDeclaredPublicMethods(Class<?> klass, String name, Class<?>... parameterTypes) {
2088                 return klass.getDeclaredPublicMethods(name, parameterTypes);
2089             }
2090             public jdk.internal.reflect.ConstantPool getConstantPool(Class<?> klass) {
2091                 return klass.getConstantPool();
2092             }
2093             public boolean casAnnotationType(Class<?> klass, AnnotationType oldType, AnnotationType newType) {
2094                 return klass.casAnnotationType(oldType, newType);
2095             }
2096             public AnnotationType getAnnotationType(Class<?> klass) {
2097                 return klass.getAnnotationType();
2098             }
2099             public Map<Class<? extends Annotation>, Annotation> getDeclaredAnnotationMap(Class<?> klass) {
2100                 return klass.getDeclaredAnnotationMap();
2101             }
2102             public byte[] getRawClassAnnotations(Class<?> klass) {
2103                 return klass.getRawAnnotations();
2104             }
2105             public byte[] getRawClassTypeAnnotations(Class<?> klass) {
2106                 return klass.getRawTypeAnnotations();
2107             }
2108             public byte[] getRawExecutableTypeAnnotations(Executable executable) {
2109                 return Class.getExecutableTypeAnnotationBytes(executable);
2110             }
2111             public <E extends Enum<E>>
2112             E[] getEnumConstantsShared(Class<E> klass) {
2113                 return klass.getEnumConstantsShared();
2114             }
2115             public void blockedOn(Thread t, Interruptible b) {
2116                 t.blockedOn(b);
2117             }
2118             public void registerShutdownHook(int slot, boolean registerShutdownInProgress, Runnable hook) {
2119                 Shutdown.add(slot, registerShutdownInProgress, hook);
2120             }
2121             public Thread newThreadWithAcc(Runnable target, AccessControlContext acc) {
2122                 return new Thread(target, acc);
2123             }
2124             @SuppressWarnings("deprecation")
2125             public void invokeFinalize(Object o) throws Throwable {
2126                 o.finalize();
2127             }
2128             public ConcurrentHashMap<?, ?> createOrGetClassLoaderValueMap(ClassLoader cl) {
2129                 return cl.createOrGetClassLoaderValueMap();
2130             }
2131             public Class<?> defineClass(ClassLoader loader, String name, byte[] b, ProtectionDomain pd, String source) {
2132                 return ClassLoader.defineClass1(loader, name, b, 0, b.length, pd, source);
2133             }
2134             public Class<?> findBootstrapClassOrNull(ClassLoader cl, String name) {
2135                 return cl.findBootstrapClassOrNull(name);
2136             }
2137             public Package definePackage(ClassLoader cl, String name, Module module) {
2138                 return cl.definePackage(name, module);
2139             }
2140             public String fastUUID(long lsb, long msb) {
2141                 return Long.fastUUID(lsb, msb);
2142             }
2143             public void addNonExportedPackages(ModuleLayer layer) {
2144                 SecurityManager.addNonExportedPackages(layer);
2145             }
2146             public void invalidatePackageAccessCache() {
2147                 SecurityManager.invalidatePackageAccessCache();
2148             }
2149             public Module defineModule(ClassLoader loader,
2150                                        ModuleDescriptor descriptor,
2151                                        URI uri) {
2152                 return new Module(null, loader, descriptor, uri);
2153             }
2154             public Module defineUnnamedModule(ClassLoader loader) {
2155                 return new Module(loader);
2156             }
2157             public void addReads(Module m1, Module m2) {
2158                 m1.implAddReads(m2);
2159             }
2160             public void addReadsAllUnnamed(Module m) {
2161                 m.implAddReadsAllUnnamed();
2162             }
2163             public void addExports(Module m, String pn, Module other) {
2164                 m.implAddExports(pn, other);
2165             }
2166             public void addExportsToAllUnnamed(Module m, String pn) {
2167                 m.implAddExportsToAllUnnamed(pn);
2168             }
2169             public void addOpens(Module m, String pn, Module other) {
2170                 m.implAddOpens(pn, other);
2171             }
2172             public void addOpensToAllUnnamed(Module m, String pn) {
2173                 m.implAddOpensToAllUnnamed(pn);
2174             }
2175             public void addOpensToAllUnnamed(Module m, Iterator<String> packages) {
2176                 m.implAddOpensToAllUnnamed(packages);
2177             }
2178             public void addUses(Module m, Class<?> service) {
2179                 m.implAddUses(service);
2180             }
2181             public boolean isReflectivelyExported(Module m, String pn, Module other) {
2182                 return m.isReflectivelyExported(pn, other);
2183             }
2184             public boolean isReflectivelyOpened(Module m, String pn, Module other) {
2185                 return m.isReflectivelyOpened(pn, other);
2186             }
2187             public ServicesCatalog getServicesCatalog(ModuleLayer layer) {
2188                 return layer.getServicesCatalog();
2189             }
2190             public Stream<ModuleLayer> layers(ModuleLayer layer) {
2191                 return layer.layers();
2192             }
2193             public Stream<ModuleLayer> layers(ClassLoader loader) {
2194                 return ModuleLayer.layers(loader);
2195             }
2196 
2197             public String newStringUTF8NoRepl(byte[] bytes, int off, int len) {
2198                 return StringCoding.newStringUTF8NoRepl(bytes, off, len);
2199             }
2200 
2201             public byte[] getBytesUTF8NoRepl(String s) {
2202                 return StringCoding.getBytesUTF8NoRepl(s);
2203             }
2204 
2205         });
2206     }
2207 }
--- EOF ---