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.Map;
  51 import java.util.Objects;
  52 import java.util.Properties;
  53 import java.util.PropertyPermission;
  54 import java.util.ResourceBundle;
  55 import java.util.function.Supplier;
  56 import java.util.concurrent.ConcurrentHashMap;
  57 import java.util.stream.Stream;
  58 
  59 import jdk.internal.loader.BootLoader;
  60 import jdk.internal.module.ModuleBootstrap;
  61 import jdk.internal.module.ServicesCatalog;
  62 import jdk.internal.reflect.CallerSensitive;
  63 import jdk.internal.reflect.Reflection;
  64 import jdk.internal.HotSpotIntrinsicCandidate;
  65 import jdk.internal.misc.JavaLangAccess;;
  66 import jdk.internal.misc.SharedSecrets;;
  67 import jdk.internal.misc.VM;
  68 import jdk.internal.logger.LoggerFinderLoader;
  69 import jdk.internal.logger.LazyLoggers;
  70 import jdk.internal.logger.LocalizedLoggerWrapper;
  71 import sun.reflect.annotation.AnnotationType;
  72 import sun.nio.ch.Interruptible;
  73 import sun.security.util.SecurityConstants;
  74 
  75 /**
  76  * The <code>System</code> class contains several useful class fields
  77  * and methods. It cannot be instantiated.
  78  *
  79  * <p>Among the facilities provided by the <code>System</code> class
  80  * are standard input, standard output, and error output streams;
  81  * access to externally defined properties and environment
  82  * variables; a means of loading files and libraries; and a utility
  83  * method for quickly copying a portion of an array.
  84  *
  85  * @author  unascribed
  86  * @since   1.0
  87  */
  88 public final class System {
  89     /* register the natives via the static initializer.
  90      *
  91      * VM will invoke the initializeSystemClass method to complete
  92      * the initialization for this class separated from clinit.
  93      * Note that to use properties set by the VM, see the constraints
  94      * described in the initializeSystemClass method.
  95      */
  96     private static native void registerNatives();
  97     static {
  98         registerNatives();
  99     }
 100 
 101     /** Don't let anyone instantiate this class */
 102     private System() {
 103     }
 104 
 105     /**
 106      * The "standard" input stream. This stream is already
 107      * open and ready to supply input data. Typically this stream
 108      * corresponds to keyboard input or another input source specified by
 109      * the host environment or user.
 110      */
 111     public static final InputStream in = null;
 112 
 113     /**
 114      * The "standard" output stream. This stream is already
 115      * open and ready to accept output data. Typically this stream
 116      * corresponds to display output or another output destination
 117      * specified by the host environment or user.
 118      * <p>
 119      * For simple stand-alone Java applications, a typical way to write
 120      * a line of output data is:
 121      * <blockquote><pre>
 122      *     System.out.println(data)
 123      * </pre></blockquote>
 124      * <p>
 125      * See the <code>println</code> methods in class <code>PrintStream</code>.
 126      *
 127      * @see     java.io.PrintStream#println()
 128      * @see     java.io.PrintStream#println(boolean)
 129      * @see     java.io.PrintStream#println(char)
 130      * @see     java.io.PrintStream#println(char[])
 131      * @see     java.io.PrintStream#println(double)
 132      * @see     java.io.PrintStream#println(float)
 133      * @see     java.io.PrintStream#println(int)
 134      * @see     java.io.PrintStream#println(long)
 135      * @see     java.io.PrintStream#println(java.lang.Object)
 136      * @see     java.io.PrintStream#println(java.lang.String)
 137      */
 138     public static final PrintStream out = null;
 139 
 140     /**
 141      * The "standard" error output stream. This stream is already
 142      * open and ready to accept output data.
 143      * <p>
 144      * Typically this stream corresponds to display output or another
 145      * output destination specified by the host environment or user. By
 146      * convention, this output stream is used to display error messages
 147      * or other information that should come to the immediate attention
 148      * of a user even if the principal output stream, the value of the
 149      * variable <code>out</code>, has been redirected to a file or other
 150      * destination that is typically not continuously monitored.
 151      */
 152     public static final PrintStream err = null;
 153 
 154     /* The security manager for the system.
 155      */
 156     private static volatile SecurityManager security;
 157 
 158     /**
 159      * Reassigns the "standard" input stream.
 160      *
 161      * <p>First, if there is a security manager, its <code>checkPermission</code>
 162      * method is called with a <code>RuntimePermission("setIO")</code> permission
 163      *  to see if it's ok to reassign the "standard" input stream.
 164      *
 165      * @param in the new standard input stream.
 166      *
 167      * @throws SecurityException
 168      *        if a security manager exists and its
 169      *        <code>checkPermission</code> method doesn't allow
 170      *        reassigning of the standard input stream.
 171      *
 172      * @see SecurityManager#checkPermission
 173      * @see java.lang.RuntimePermission
 174      *
 175      * @since   1.1
 176      */
 177     public static void setIn(InputStream in) {
 178         checkIO();
 179         setIn0(in);
 180     }
 181 
 182     /**
 183      * Reassigns the "standard" output stream.
 184      *
 185      * <p>First, if there is a security manager, its <code>checkPermission</code>
 186      * method is called with a <code>RuntimePermission("setIO")</code> permission
 187      *  to see if it's ok to reassign the "standard" output stream.
 188      *
 189      * @param out the new standard output stream
 190      *
 191      * @throws SecurityException
 192      *        if a security manager exists and its
 193      *        <code>checkPermission</code> method doesn't allow
 194      *        reassigning of the standard output stream.
 195      *
 196      * @see SecurityManager#checkPermission
 197      * @see java.lang.RuntimePermission
 198      *
 199      * @since   1.1
 200      */
 201     public static void setOut(PrintStream out) {
 202         checkIO();
 203         setOut0(out);
 204     }
 205 
 206     /**
 207      * Reassigns the "standard" error output stream.
 208      *
 209      * <p>First, if there is a security manager, its <code>checkPermission</code>
 210      * method is called with a <code>RuntimePermission("setIO")</code> permission
 211      *  to see if it's ok to reassign the "standard" error output stream.
 212      *
 213      * @param err the new standard error output stream.
 214      *
 215      * @throws SecurityException
 216      *        if a security manager exists and its
 217      *        <code>checkPermission</code> method doesn't allow
 218      *        reassigning of the standard error output stream.
 219      *
 220      * @see SecurityManager#checkPermission
 221      * @see java.lang.RuntimePermission
 222      *
 223      * @since   1.1
 224      */
 225     public static void setErr(PrintStream err) {
 226         checkIO();
 227         setErr0(err);
 228     }
 229 
 230     private static volatile Console cons;
 231     /**
 232      * Returns the unique {@link java.io.Console Console} object associated
 233      * with the current Java virtual machine, if any.
 234      *
 235      * @return  The system console, if any, otherwise {@code null}.
 236      *
 237      * @since   1.6
 238      */
 239      public static Console console() {
 240          Console c;
 241          if ((c = cons) == null) {
 242              synchronized (System.class) {
 243                  if ((c = cons) == null) {
 244                      cons = c = SharedSecrets.getJavaIOAccess().console();
 245                  }
 246              }
 247          }
 248          return c;
 249      }
 250 
 251     /**
 252      * Returns the channel inherited from the entity that created this
 253      * Java virtual machine.
 254      *
 255      * <p> This method returns the channel obtained by invoking the
 256      * {@link java.nio.channels.spi.SelectorProvider#inheritedChannel
 257      * inheritedChannel} method of the system-wide default
 258      * {@link java.nio.channels.spi.SelectorProvider} object. </p>
 259      *
 260      * <p> In addition to the network-oriented channels described in
 261      * {@link java.nio.channels.spi.SelectorProvider#inheritedChannel
 262      * inheritedChannel}, this method may return other kinds of
 263      * channels in the future.
 264      *
 265      * @return  The inherited channel, if any, otherwise {@code null}.
 266      *
 267      * @throws  IOException
 268      *          If an I/O error occurs
 269      *
 270      * @throws  SecurityException
 271      *          If a security manager is present and it does not
 272      *          permit access to the channel.
 273      *
 274      * @since 1.5
 275      */
 276     public static Channel inheritedChannel() throws IOException {
 277         return SelectorProvider.provider().inheritedChannel();
 278     }
 279 
 280     private static void checkIO() {
 281         SecurityManager sm = getSecurityManager();
 282         if (sm != null) {
 283             sm.checkPermission(new RuntimePermission("setIO"));
 284         }
 285     }
 286 
 287     private static native void setIn0(InputStream in);
 288     private static native void setOut0(PrintStream out);
 289     private static native void setErr0(PrintStream err);
 290 
 291     /**
 292      * Sets the System security.
 293      *
 294      * <p> If there is a security manager already installed, this method first
 295      * calls the security manager's <code>checkPermission</code> method
 296      * with a <code>RuntimePermission("setSecurityManager")</code>
 297      * permission to ensure it's ok to replace the existing
 298      * security manager.
 299      * This may result in throwing a <code>SecurityException</code>.
 300      *
 301      * <p> Otherwise, the argument is established as the current
 302      * security manager. If the argument is <code>null</code> and no
 303      * security manager has been established, then no action is taken and
 304      * the method simply returns.
 305      *
 306      * @param      s   the security manager.
 307      * @exception  SecurityException  if the security manager has already
 308      *             been set and its <code>checkPermission</code> method
 309      *             doesn't allow it to be replaced.
 310      * @see #getSecurityManager
 311      * @see SecurityManager#checkPermission
 312      * @see java.lang.RuntimePermission
 313      */
 314     public static void setSecurityManager(final SecurityManager s) {
 315         if (s != null) {
 316             try {
 317                 s.checkPackageAccess("java.lang");
 318             } catch (Exception e) {
 319                 // no-op
 320             }
 321         }
 322         setSecurityManager0(s);
 323     }
 324 
 325     private static synchronized
 326     void setSecurityManager0(final SecurityManager s) {
 327         SecurityManager sm = getSecurityManager();
 328         if (sm != null) {
 329             // ask the currently installed security manager if we
 330             // can replace it.
 331             sm.checkPermission(new RuntimePermission
 332                                      ("setSecurityManager"));
 333         }
 334 
 335         if ((s != null) && (s.getClass().getClassLoader() != null)) {
 336             // New security manager class is not on bootstrap classpath.
 337             // Cause policy to get initialized before we install the new
 338             // security manager, in order to prevent infinite loops when
 339             // trying to initialize the policy (which usually involves
 340             // accessing some security and/or system properties, which in turn
 341             // calls the installed security manager's checkPermission method
 342             // which will loop infinitely if there is a non-system class
 343             // (in this case: the new security manager class) on the stack).
 344             AccessController.doPrivileged(new PrivilegedAction<>() {
 345                 public Object run() {
 346                     s.getClass().getProtectionDomain().implies
 347                         (SecurityConstants.ALL_PERMISSION);
 348                     return null;
 349                 }
 350             });
 351         }
 352 
 353         security = s;
 354     }
 355 
 356     /**
 357      * Gets the system security interface.
 358      *
 359      * @return  if a security manager has already been established for the
 360      *          current application, then that security manager is returned;
 361      *          otherwise, <code>null</code> is returned.
 362      * @see     #setSecurityManager
 363      */
 364     public static SecurityManager getSecurityManager() {
 365         return security;
 366     }
 367 
 368     /**
 369      * Returns the current time in milliseconds.  Note that
 370      * while the unit of time of the return value is a millisecond,
 371      * the granularity of the value depends on the underlying
 372      * operating system and may be larger.  For example, many
 373      * operating systems measure time in units of tens of
 374      * milliseconds.
 375      *
 376      * <p> See the description of the class <code>Date</code> for
 377      * a discussion of slight discrepancies that may arise between
 378      * "computer time" and coordinated universal time (UTC).
 379      *
 380      * @return  the difference, measured in milliseconds, between
 381      *          the current time and midnight, January 1, 1970 UTC.
 382      * @see     java.util.Date
 383      */
 384     @HotSpotIntrinsicCandidate
 385     public static native long currentTimeMillis();
 386 
 387     /**
 388      * Returns the current value of the running Java Virtual Machine's
 389      * high-resolution time source, in nanoseconds.
 390      *
 391      * <p>This method can only be used to measure elapsed time and is
 392      * not related to any other notion of system or wall-clock time.
 393      * The value returned represents nanoseconds since some fixed but
 394      * arbitrary <i>origin</i> time (perhaps in the future, so values
 395      * may be negative).  The same origin is used by all invocations of
 396      * this method in an instance of a Java virtual machine; other
 397      * virtual machine instances are likely to use a different origin.
 398      *
 399      * <p>This method provides nanosecond precision, but not necessarily
 400      * nanosecond resolution (that is, how frequently the value changes)
 401      * - no guarantees are made except that the resolution is at least as
 402      * good as that of {@link #currentTimeMillis()}.
 403      *
 404      * <p>Differences in successive calls that span greater than
 405      * approximately 292 years (2<sup>63</sup> nanoseconds) will not
 406      * correctly compute elapsed time due to numerical overflow.
 407      *
 408      * <p>The values returned by this method become meaningful only when
 409      * the difference between two such values, obtained within the same
 410      * instance of a Java virtual machine, is computed.
 411      *
 412      * <p>For example, to measure how long some code takes to execute:
 413      * <pre> {@code
 414      * long startTime = System.nanoTime();
 415      * // ... the code being measured ...
 416      * long elapsedNanos = System.nanoTime() - startTime;}</pre>
 417      *
 418      * <p>To compare elapsed time against a timeout, use <pre> {@code
 419      * if (System.nanoTime() - startTime >= timeoutNanos) ...}</pre>
 420      * instead of <pre> {@code
 421      * if (System.nanoTime() >= startTime + timeoutNanos) ...}</pre>
 422      * because of the possibility of numerical overflow.
 423      *
 424      * @return the current value of the running Java Virtual Machine's
 425      *         high-resolution time source, in nanoseconds
 426      * @since 1.5
 427      */
 428     @HotSpotIntrinsicCandidate
 429     public static native long nanoTime();
 430 
 431     /**
 432      * Copies an array from the specified source array, beginning at the
 433      * specified position, to the specified position of the destination array.
 434      * A subsequence of array components are copied from the source
 435      * array referenced by <code>src</code> to the destination array
 436      * referenced by <code>dest</code>. The number of components copied is
 437      * equal to the <code>length</code> argument. The components at
 438      * positions <code>srcPos</code> through
 439      * <code>srcPos+length-1</code> in the source array are copied into
 440      * positions <code>destPos</code> through
 441      * <code>destPos+length-1</code>, respectively, of the destination
 442      * array.
 443      * <p>
 444      * If the <code>src</code> and <code>dest</code> arguments refer to the
 445      * same array object, then the copying is performed as if the
 446      * components at positions <code>srcPos</code> through
 447      * <code>srcPos+length-1</code> were first copied to a temporary
 448      * array with <code>length</code> components and then the contents of
 449      * the temporary array were copied into positions
 450      * <code>destPos</code> through <code>destPos+length-1</code> of the
 451      * destination array.
 452      * <p>
 453      * If <code>dest</code> is <code>null</code>, then a
 454      * <code>NullPointerException</code> is thrown.
 455      * <p>
 456      * If <code>src</code> is <code>null</code>, then a
 457      * <code>NullPointerException</code> is thrown and the destination
 458      * array is not modified.
 459      * <p>
 460      * Otherwise, if any of the following is true, an
 461      * <code>ArrayStoreException</code> is thrown and the destination is
 462      * not modified:
 463      * <ul>
 464      * <li>The <code>src</code> argument refers to an object that is not an
 465      *     array.
 466      * <li>The <code>dest</code> argument refers to an object that is not an
 467      *     array.
 468      * <li>The <code>src</code> argument and <code>dest</code> argument refer
 469      *     to arrays whose component types are different primitive types.
 470      * <li>The <code>src</code> argument refers to an array with a primitive
 471      *    component type and the <code>dest</code> argument refers to an array
 472      *     with a reference component type.
 473      * <li>The <code>src</code> argument refers to an array with a reference
 474      *    component type and the <code>dest</code> argument refers to an array
 475      *     with a primitive component type.
 476      * </ul>
 477      * <p>
 478      * Otherwise, if any of the following is true, an
 479      * <code>IndexOutOfBoundsException</code> is
 480      * thrown and the destination is not modified:
 481      * <ul>
 482      * <li>The <code>srcPos</code> argument is negative.
 483      * <li>The <code>destPos</code> argument is negative.
 484      * <li>The <code>length</code> argument is negative.
 485      * <li><code>srcPos+length</code> is greater than
 486      *     <code>src.length</code>, the length of the source array.
 487      * <li><code>destPos+length</code> is greater than
 488      *     <code>dest.length</code>, the length of the destination array.
 489      * </ul>
 490      * <p>
 491      * Otherwise, if any actual component of the source array from
 492      * position <code>srcPos</code> through
 493      * <code>srcPos+length-1</code> cannot be converted to the component
 494      * type of the destination array by assignment conversion, an
 495      * <code>ArrayStoreException</code> is thrown. In this case, let
 496      * <b><i>k</i></b> be the smallest nonnegative integer less than
 497      * length such that <code>src[srcPos+</code><i>k</i><code>]</code>
 498      * cannot be converted to the component type of the destination
 499      * array; when the exception is thrown, source array components from
 500      * positions <code>srcPos</code> through
 501      * <code>srcPos+</code><i>k</i><code>-1</code>
 502      * will already have been copied to destination array positions
 503      * <code>destPos</code> through
 504      * <code>destPos+</code><i>k</I><code>-1</code> and no other
 505      * positions of the destination array will have been modified.
 506      * (Because of the restrictions already itemized, this
 507      * paragraph effectively applies only to the situation where both
 508      * arrays have component types that are reference types.)
 509      *
 510      * @param      src      the source array.
 511      * @param      srcPos   starting position in the source array.
 512      * @param      dest     the destination array.
 513      * @param      destPos  starting position in the destination data.
 514      * @param      length   the number of array elements to be copied.
 515      * @exception  IndexOutOfBoundsException  if copying would cause
 516      *               access of data outside array bounds.
 517      * @exception  ArrayStoreException  if an element in the <code>src</code>
 518      *               array could not be stored into the <code>dest</code> array
 519      *               because of a type mismatch.
 520      * @exception  NullPointerException if either <code>src</code> or
 521      *               <code>dest</code> is <code>null</code>.
 522      */
 523     @HotSpotIntrinsicCandidate
 524     public static native void arraycopy(Object src,  int  srcPos,
 525                                         Object dest, int destPos,
 526                                         int length);
 527 
 528     /**
 529      * Returns the same hash code for the given object as
 530      * would be returned by the default method hashCode(),
 531      * whether or not the given object's class overrides
 532      * hashCode().
 533      * The hash code for the null reference is zero.
 534      *
 535      * @param x object for which the hashCode is to be calculated
 536      * @return  the hashCode
 537      * @since   1.1
 538      * @see Object#hashCode
 539      * @see java.util.Objects#hashCode(Object)
 540      */
 541     @HotSpotIntrinsicCandidate
 542     public static native int identityHashCode(Object x);
 543 
 544     /**
 545      * System properties. The following properties are guaranteed to be defined:
 546      * <dl>
 547      * <dt>java.version         <dd>Java version number
 548      * <dt>java.vendor          <dd>Java vendor specific string
 549      * <dt>java.vendor.url      <dd>Java vendor URL
 550      * <dt>java.home            <dd>Java installation directory
 551      * <dt>java.class.version   <dd>Java class version number
 552      * <dt>java.class.path      <dd>Java classpath
 553      * <dt>os.name              <dd>Operating System Name
 554      * <dt>os.arch              <dd>Operating System Architecture
 555      * <dt>os.version           <dd>Operating System Version
 556      * <dt>file.separator       <dd>File separator ("/" on Unix)
 557      * <dt>path.separator       <dd>Path separator (":" on Unix)
 558      * <dt>line.separator       <dd>Line separator ("\n" on Unix)
 559      * <dt>user.name            <dd>User account name
 560      * <dt>user.home            <dd>User home directory
 561      * <dt>user.dir             <dd>User's current working directory
 562      * </dl>
 563      */
 564 
 565     private static Properties props;
 566     private static native Properties initProperties(Properties props);
 567 
 568     /**
 569      * Determines the current system properties.
 570      * <p>
 571      * First, if there is a security manager, its
 572      * <code>checkPropertiesAccess</code> method is called with no
 573      * arguments. This may result in a security exception.
 574      * <p>
 575      * The current set of system properties for use by the
 576      * {@link #getProperty(String)} method is returned as a
 577      * <code>Properties</code> object. If there is no current set of
 578      * system properties, a set of system properties is first created and
 579      * initialized. This set of system properties always includes values
 580      * for the following keys:
 581      * <table summary="Shows property keys and associated values">
 582      * <tr><th>Key</th>
 583      *     <th>Description of Associated Value</th></tr>
 584      * <tr><td><code>java.version</code></td>
 585      *     <td>Java Runtime Environment version which may be interpreted
 586      *     as a {@link Runtime.Version}</td></tr>
 587      * <tr><td><code>java.vendor</code></td>
 588      *     <td>Java Runtime Environment vendor</td></tr>
 589      * <tr><td><code>java.vendor.url</code></td>
 590      *     <td>Java vendor URL</td></tr>
 591      * <tr><td><code>java.home</code></td>
 592      *     <td>Java installation directory</td></tr>
 593      * <tr><td><code>java.vm.specification.version</code></td>
 594      *     <td>Java Virtual Machine specification version which may be
 595      *     interpreted as a {@link Runtime.Version}</td></tr>
 596      * <tr><td><code>java.vm.specification.vendor</code></td>
 597      *     <td>Java Virtual Machine specification vendor</td></tr>
 598      * <tr><td><code>java.vm.specification.name</code></td>
 599      *     <td>Java Virtual Machine specification name</td></tr>
 600      * <tr><td><code>java.vm.version</code></td>
 601      *     <td>Java Virtual Machine implementation version which may be
 602      *     interpreted as a {@link Runtime.Version}</td></tr>
 603      * <tr><td><code>java.vm.vendor</code></td>
 604      *     <td>Java Virtual Machine implementation vendor</td></tr>
 605      * <tr><td><code>java.vm.name</code></td>
 606      *     <td>Java Virtual Machine implementation name</td></tr>
 607      * <tr><td><code>java.specification.version</code></td>
 608      *     <td>Java Runtime Environment specification version which may be
 609      *     interpreted as a {@link Runtime.Version}</td></tr>
 610      * <tr><td><code>java.specification.vendor</code></td>
 611      *     <td>Java Runtime Environment specification  vendor</td></tr>
 612      * <tr><td><code>java.specification.name</code></td>
 613      *     <td>Java Runtime Environment specification  name</td></tr>
 614      * <tr><td><code>java.class.version</code></td>
 615      *     <td>Java class format version number</td></tr>
 616      * <tr><td><code>java.class.path</code></td>
 617      *     <td>Java class path</td></tr>
 618      * <tr><td><code>java.library.path</code></td>
 619      *     <td>List of paths to search when loading libraries</td></tr>
 620      * <tr><td><code>java.io.tmpdir</code></td>
 621      *     <td>Default temp file path</td></tr>
 622      * <tr><td><code>java.compiler</code></td>
 623      *     <td>Name of JIT compiler to use</td></tr>
 624      * <tr><td><code>os.name</code></td>
 625      *     <td>Operating system name</td></tr>
 626      * <tr><td><code>os.arch</code></td>
 627      *     <td>Operating system architecture</td></tr>
 628      * <tr><td><code>os.version</code></td>
 629      *     <td>Operating system version</td></tr>
 630      * <tr><td><code>file.separator</code></td>
 631      *     <td>File separator ("/" on UNIX)</td></tr>
 632      * <tr><td><code>path.separator</code></td>
 633      *     <td>Path separator (":" on UNIX)</td></tr>
 634      * <tr><td><code>line.separator</code></td>
 635      *     <td>Line separator ("\n" on UNIX)</td></tr>
 636      * <tr><td><code>user.name</code></td>
 637      *     <td>User's account name</td></tr>
 638      * <tr><td><code>user.home</code></td>
 639      *     <td>User's home directory</td></tr>
 640      * <tr><td><code>user.dir</code></td>
 641      *     <td>User's current working directory</td></tr>
 642      * </table>
 643      * <p>
 644      * Multiple paths in a system property value are separated by the path
 645      * separator character of the platform.
 646      * <p>
 647      * Note that even if the security manager does not permit the
 648      * <code>getProperties</code> operation, it may choose to permit the
 649      * {@link #getProperty(String)} operation.
 650      *
 651      * @implNote In addition to the standard system properties, the system
 652      * properties may include the following keys:
 653      * <table summary="Shows property keys and associated values">
 654      * <tr><th>Key</th>
 655      *     <th>Description of Associated Value</th></tr>
 656      * <tr><td>{@code jdk.module.path}</td>
 657      *     <td>The application module path</td></tr>
 658      * <tr><td>{@code jdk.module.upgrade.path}</td>
 659      *     <td>The upgrade module path</td></tr>
 660      * <tr><td>{@code jdk.module.main}</td>
 661      *     <td>The module name of the initial/main module</td></tr>
 662      * <tr><td>{@code jdk.module.main.class}</td>
 663      *     <td>The main class name of the initial module</td></tr>
 664      * </table>
 665      *
 666      * @return     the system properties
 667      * @exception  SecurityException  if a security manager exists and its
 668      *             <code>checkPropertiesAccess</code> method doesn't allow access
 669      *              to the system properties.
 670      * @see        #setProperties
 671      * @see        java.lang.SecurityException
 672      * @see        java.lang.SecurityManager#checkPropertiesAccess()
 673      * @see        java.util.Properties
 674      */
 675     public static Properties getProperties() {
 676         SecurityManager sm = getSecurityManager();
 677         if (sm != null) {
 678             sm.checkPropertiesAccess();
 679         }
 680 
 681         return props;
 682     }
 683 
 684     /**
 685      * Returns the system-dependent line separator string.  It always
 686      * returns the same value - the initial value of the {@linkplain
 687      * #getProperty(String) system property} {@code line.separator}.
 688      *
 689      * <p>On UNIX systems, it returns {@code "\n"}; on Microsoft
 690      * Windows systems it returns {@code "\r\n"}.
 691      *
 692      * @return the system-dependent line separator string
 693      * @since 1.7
 694      */
 695     public static String lineSeparator() {
 696         return lineSeparator;
 697     }
 698 
 699     private static String lineSeparator;
 700 
 701     /**
 702      * Sets the system properties to the <code>Properties</code>
 703      * argument.
 704      * <p>
 705      * First, if there is a security manager, its
 706      * <code>checkPropertiesAccess</code> method is called with no
 707      * arguments. This may result in a security exception.
 708      * <p>
 709      * The argument becomes the current set of system properties for use
 710      * by the {@link #getProperty(String)} method. If the argument is
 711      * <code>null</code>, then the current set of system properties is
 712      * forgotten.
 713      *
 714      * @param      props   the new system properties.
 715      * @exception  SecurityException  if a security manager exists and its
 716      *             <code>checkPropertiesAccess</code> method doesn't allow access
 717      *              to the system properties.
 718      * @see        #getProperties
 719      * @see        java.util.Properties
 720      * @see        java.lang.SecurityException
 721      * @see        java.lang.SecurityManager#checkPropertiesAccess()
 722      */
 723     public static void setProperties(Properties props) {
 724         SecurityManager sm = getSecurityManager();
 725         if (sm != null) {
 726             sm.checkPropertiesAccess();
 727         }
 728         if (props == null) {
 729             props = new Properties();
 730             initProperties(props);
 731         }
 732         System.props = props;
 733     }
 734 
 735     /**
 736      * Gets the system property indicated by the specified key.
 737      * <p>
 738      * First, if there is a security manager, its
 739      * <code>checkPropertyAccess</code> method is called with the key as
 740      * its argument. This may result in a SecurityException.
 741      * <p>
 742      * If there is no current set of system properties, a set of system
 743      * properties is first created and initialized in the same manner as
 744      * for the <code>getProperties</code> method.
 745      *
 746      * @param      key   the name of the system property.
 747      * @return     the string value of the system property,
 748      *             or <code>null</code> if there is no property with that key.
 749      *
 750      * @exception  SecurityException  if a security manager exists and its
 751      *             <code>checkPropertyAccess</code> method doesn't allow
 752      *              access to the specified system property.
 753      * @exception  NullPointerException if <code>key</code> is
 754      *             <code>null</code>.
 755      * @exception  IllegalArgumentException if <code>key</code> is empty.
 756      * @see        #setProperty
 757      * @see        java.lang.SecurityException
 758      * @see        java.lang.SecurityManager#checkPropertyAccess(java.lang.String)
 759      * @see        java.lang.System#getProperties()
 760      */
 761     public static String getProperty(String key) {
 762         checkKey(key);
 763         SecurityManager sm = getSecurityManager();
 764         if (sm != null) {
 765             sm.checkPropertyAccess(key);
 766         }
 767 
 768         return props.getProperty(key);
 769     }
 770 
 771     /**
 772      * Gets the system property indicated by the specified key.
 773      * <p>
 774      * First, if there is a security manager, its
 775      * <code>checkPropertyAccess</code> method is called with the
 776      * <code>key</code> as its argument.
 777      * <p>
 778      * If there is no current set of system properties, a set of system
 779      * properties is first created and initialized in the same manner as
 780      * for the <code>getProperties</code> method.
 781      *
 782      * @param      key   the name of the system property.
 783      * @param      def   a default value.
 784      * @return     the string value of the system property,
 785      *             or the default value if there is no property with that key.
 786      *
 787      * @exception  SecurityException  if a security manager exists and its
 788      *             <code>checkPropertyAccess</code> method doesn't allow
 789      *             access to the specified system property.
 790      * @exception  NullPointerException if <code>key</code> is
 791      *             <code>null</code>.
 792      * @exception  IllegalArgumentException if <code>key</code> is empty.
 793      * @see        #setProperty
 794      * @see        java.lang.SecurityManager#checkPropertyAccess(java.lang.String)
 795      * @see        java.lang.System#getProperties()
 796      */
 797     public static String getProperty(String key, String def) {
 798         checkKey(key);
 799         SecurityManager sm = getSecurityManager();
 800         if (sm != null) {
 801             sm.checkPropertyAccess(key);
 802         }
 803 
 804         return props.getProperty(key, def);
 805     }
 806 
 807     /**
 808      * Sets the system property indicated by the specified key.
 809      * <p>
 810      * First, if a security manager exists, its
 811      * <code>SecurityManager.checkPermission</code> method
 812      * is called with a <code>PropertyPermission(key, "write")</code>
 813      * permission. This may result in a SecurityException being thrown.
 814      * If no exception is thrown, the specified property is set to the given
 815      * value.
 816      *
 817      * @param      key   the name of the system property.
 818      * @param      value the value of the system property.
 819      * @return     the previous value of the system property,
 820      *             or <code>null</code> if it did not have one.
 821      *
 822      * @exception  SecurityException  if a security manager exists and its
 823      *             <code>checkPermission</code> method doesn't allow
 824      *             setting of the specified property.
 825      * @exception  NullPointerException if <code>key</code> or
 826      *             <code>value</code> is <code>null</code>.
 827      * @exception  IllegalArgumentException if <code>key</code> is empty.
 828      * @see        #getProperty
 829      * @see        java.lang.System#getProperty(java.lang.String)
 830      * @see        java.lang.System#getProperty(java.lang.String, java.lang.String)
 831      * @see        java.util.PropertyPermission
 832      * @see        SecurityManager#checkPermission
 833      * @since      1.2
 834      */
 835     public static String setProperty(String key, String value) {
 836         checkKey(key);
 837         SecurityManager sm = getSecurityManager();
 838         if (sm != null) {
 839             sm.checkPermission(new PropertyPermission(key,
 840                 SecurityConstants.PROPERTY_WRITE_ACTION));
 841         }
 842 
 843         return (String) props.setProperty(key, value);
 844     }
 845 
 846     /**
 847      * Removes the system property indicated by the specified key.
 848      * <p>
 849      * First, if a security manager exists, its
 850      * <code>SecurityManager.checkPermission</code> method
 851      * is called with a <code>PropertyPermission(key, "write")</code>
 852      * permission. This may result in a SecurityException being thrown.
 853      * If no exception is thrown, the specified property is removed.
 854      *
 855      * @param      key   the name of the system property to be removed.
 856      * @return     the previous string value of the system property,
 857      *             or <code>null</code> if there was no property with that key.
 858      *
 859      * @exception  SecurityException  if a security manager exists and its
 860      *             <code>checkPropertyAccess</code> method doesn't allow
 861      *              access to the specified system property.
 862      * @exception  NullPointerException if <code>key</code> is
 863      *             <code>null</code>.
 864      * @exception  IllegalArgumentException if <code>key</code> is empty.
 865      * @see        #getProperty
 866      * @see        #setProperty
 867      * @see        java.util.Properties
 868      * @see        java.lang.SecurityException
 869      * @see        java.lang.SecurityManager#checkPropertiesAccess()
 870      * @since 1.5
 871      */
 872     public static String clearProperty(String key) {
 873         checkKey(key);
 874         SecurityManager sm = getSecurityManager();
 875         if (sm != null) {
 876             sm.checkPermission(new PropertyPermission(key, "write"));
 877         }
 878 
 879         return (String) props.remove(key);
 880     }
 881 
 882     private static void checkKey(String key) {
 883         if (key == null) {
 884             throw new NullPointerException("key can't be null");
 885         }
 886         if (key.equals("")) {
 887             throw new IllegalArgumentException("key can't be empty");
 888         }
 889     }
 890 
 891     /**
 892      * Gets the value of the specified environment variable. An
 893      * environment variable is a system-dependent external named
 894      * value.
 895      *
 896      * <p>If a security manager exists, its
 897      * {@link SecurityManager#checkPermission checkPermission}
 898      * method is called with a
 899      * <code>{@link RuntimePermission}("getenv."+name)</code>
 900      * permission.  This may result in a {@link SecurityException}
 901      * being thrown.  If no exception is thrown the value of the
 902      * variable <code>name</code> is returned.
 903      *
 904      * <p><a id="EnvironmentVSSystemProperties"><i>System
 905      * properties</i> and <i>environment variables</i></a> are both
 906      * conceptually mappings between names and values.  Both
 907      * mechanisms can be used to pass user-defined information to a
 908      * Java process.  Environment variables have a more global effect,
 909      * because they are visible to all descendants of the process
 910      * which defines them, not just the immediate Java subprocess.
 911      * They can have subtly different semantics, such as case
 912      * insensitivity, on different operating systems.  For these
 913      * reasons, environment variables are more likely to have
 914      * unintended side effects.  It is best to use system properties
 915      * where possible.  Environment variables should be used when a
 916      * global effect is desired, or when an external system interface
 917      * requires an environment variable (such as <code>PATH</code>).
 918      *
 919      * <p>On UNIX systems the alphabetic case of <code>name</code> is
 920      * typically significant, while on Microsoft Windows systems it is
 921      * typically not.  For example, the expression
 922      * <code>System.getenv("FOO").equals(System.getenv("foo"))</code>
 923      * is likely to be true on Microsoft Windows.
 924      *
 925      * @param  name the name of the environment variable
 926      * @return the string value of the variable, or <code>null</code>
 927      *         if the variable is not defined in the system environment
 928      * @throws NullPointerException if <code>name</code> is <code>null</code>
 929      * @throws SecurityException
 930      *         if a security manager exists and its
 931      *         {@link SecurityManager#checkPermission checkPermission}
 932      *         method doesn't allow access to the environment variable
 933      *         <code>name</code>
 934      * @see    #getenv()
 935      * @see    ProcessBuilder#environment()
 936      */
 937     public static String getenv(String name) {
 938         SecurityManager sm = getSecurityManager();
 939         if (sm != null) {
 940             sm.checkPermission(new RuntimePermission("getenv."+name));
 941         }
 942 
 943         return ProcessEnvironment.getenv(name);
 944     }
 945 
 946 
 947     /**
 948      * Returns an unmodifiable string map view of the current system environment.
 949      * The environment is a system-dependent mapping from names to
 950      * values which is passed from parent to child processes.
 951      *
 952      * <p>If the system does not support environment variables, an
 953      * empty map is returned.
 954      *
 955      * <p>The returned map will never contain null keys or values.
 956      * Attempting to query the presence of a null key or value will
 957      * throw a {@link NullPointerException}.  Attempting to query
 958      * the presence of a key or value which is not of type
 959      * {@link String} will throw a {@link ClassCastException}.
 960      *
 961      * <p>The returned map and its collection views may not obey the
 962      * general contract of the {@link Object#equals} and
 963      * {@link Object#hashCode} methods.
 964      *
 965      * <p>The returned map is typically case-sensitive on all platforms.
 966      *
 967      * <p>If a security manager exists, its
 968      * {@link SecurityManager#checkPermission checkPermission}
 969      * method is called with a
 970      * <code>{@link RuntimePermission}("getenv.*")</code>
 971      * permission.  This may result in a {@link SecurityException} being
 972      * thrown.
 973      *
 974      * <p>When passing information to a Java subprocess,
 975      * <a href=#EnvironmentVSSystemProperties>system properties</a>
 976      * are generally preferred over environment variables.
 977      *
 978      * @return the environment as a map of variable names to values
 979      * @throws SecurityException
 980      *         if a security manager exists and its
 981      *         {@link SecurityManager#checkPermission checkPermission}
 982      *         method doesn't allow access to the process environment
 983      * @see    #getenv(String)
 984      * @see    ProcessBuilder#environment()
 985      * @since  1.5
 986      */
 987     public static java.util.Map<String,String> getenv() {
 988         SecurityManager sm = getSecurityManager();
 989         if (sm != null) {
 990             sm.checkPermission(new RuntimePermission("getenv.*"));
 991         }
 992 
 993         return ProcessEnvironment.getenv();
 994     }
 995 
 996     /**
 997      * {@code System.Logger} instances log messages that will be
 998      * routed to the underlying logging framework the {@link System.LoggerFinder
 999      * LoggerFinder} uses.
1000      * <p>
1001      * {@code System.Logger} instances are typically obtained from
1002      * the {@link java.lang.System System} class, by calling
1003      * {@link java.lang.System#getLogger(java.lang.String) System.getLogger(loggerName)}
1004      * or {@link java.lang.System#getLogger(java.lang.String, java.util.ResourceBundle)
1005      * System.getLogger(loggerName, bundle)}.
1006      *
1007      * @see java.lang.System#getLogger(java.lang.String)
1008      * @see java.lang.System#getLogger(java.lang.String, java.util.ResourceBundle)
1009      * @see java.lang.System.LoggerFinder
1010      *
1011      * @since 9
1012      *
1013      */
1014     public interface Logger {
1015 
1016         /**
1017          * System {@linkplain Logger loggers} levels.
1018          * <p>
1019          * A level has a {@linkplain #getName() name} and {@linkplain
1020          * #getSeverity() severity}.
1021          * Level values are {@link #ALL}, {@link #TRACE}, {@link #DEBUG},
1022          * {@link #INFO}, {@link #WARNING}, {@link #ERROR}, {@link #OFF},
1023          * by order of increasing severity.
1024          * <br>
1025          * {@link #ALL} and {@link #OFF}
1026          * are simple markers with severities mapped respectively to
1027          * {@link java.lang.Integer#MIN_VALUE Integer.MIN_VALUE} and
1028          * {@link java.lang.Integer#MAX_VALUE Integer.MAX_VALUE}.
1029          * <p>
1030          * <b>Severity values and Mapping to {@code java.util.logging.Level}.</b>
1031          * <p>
1032          * {@linkplain System.Logger.Level System logger levels} are mapped to
1033          * {@linkplain java.util.logging.Level  java.util.logging levels}
1034          * of corresponding severity.
1035          * <br>The mapping is as follows:
1036          * <br><br>
1037          * <table border="1">
1038          * <caption>System.Logger Severity Level Mapping</caption>
1039          * <tr><td><b>System.Logger Levels</b></td>
1040          * <td>{@link Logger.Level#ALL ALL}</td>
1041          * <td>{@link Logger.Level#TRACE TRACE}</td>
1042          * <td>{@link Logger.Level#DEBUG DEBUG}</td>
1043          * <td>{@link Logger.Level#INFO INFO}</td>
1044          * <td>{@link Logger.Level#WARNING WARNING}</td>
1045          * <td>{@link Logger.Level#ERROR ERROR}</td>
1046          * <td>{@link Logger.Level#OFF OFF}</td>
1047          * </tr>
1048          * <tr><td><b>java.util.logging Levels</b></td>
1049          * <td>{@link java.util.logging.Level#ALL ALL}</td>
1050          * <td>{@link java.util.logging.Level#FINER FINER}</td>
1051          * <td>{@link java.util.logging.Level#FINE FINE}</td>
1052          * <td>{@link java.util.logging.Level#INFO INFO}</td>
1053          * <td>{@link java.util.logging.Level#WARNING WARNING}</td>
1054          * <td>{@link java.util.logging.Level#SEVERE SEVERE}</td>
1055          * <td>{@link java.util.logging.Level#OFF OFF}</td>
1056          * </tr>
1057          * </table>
1058          *
1059          * @since 9
1060          *
1061          * @see java.lang.System.LoggerFinder
1062          * @see java.lang.System.Logger
1063          */
1064         public enum Level {
1065 
1066             // for convenience, we're reusing java.util.logging.Level int values
1067             // the mapping logic in sun.util.logging.PlatformLogger depends
1068             // on this.
1069             /**
1070              * A marker to indicate that all levels are enabled.
1071              * This level {@linkplain #getSeverity() severity} is
1072              * {@link Integer#MIN_VALUE}.
1073              */
1074             ALL(Integer.MIN_VALUE),  // typically mapped to/from j.u.l.Level.ALL
1075             /**
1076              * {@code TRACE} level: usually used to log diagnostic information.
1077              * This level {@linkplain #getSeverity() severity} is
1078              * {@code 400}.
1079              */
1080             TRACE(400),   // typically mapped to/from j.u.l.Level.FINER
1081             /**
1082              * {@code DEBUG} level: usually used to log debug information traces.
1083              * This level {@linkplain #getSeverity() severity} is
1084              * {@code 500}.
1085              */
1086             DEBUG(500),   // typically mapped to/from j.u.l.Level.FINEST/FINE/CONFIG
1087             /**
1088              * {@code INFO} level: usually used to log information messages.
1089              * This level {@linkplain #getSeverity() severity} is
1090              * {@code 800}.
1091              */
1092             INFO(800),    // typically mapped to/from j.u.l.Level.INFO
1093             /**
1094              * {@code WARNING} level: usually used to log warning messages.
1095              * This level {@linkplain #getSeverity() severity} is
1096              * {@code 900}.
1097              */
1098             WARNING(900), // typically mapped to/from j.u.l.Level.WARNING
1099             /**
1100              * {@code ERROR} level: usually used to log error messages.
1101              * This level {@linkplain #getSeverity() severity} is
1102              * {@code 1000}.
1103              */
1104             ERROR(1000),  // typically mapped to/from j.u.l.Level.SEVERE
1105             /**
1106              * A marker to indicate that all levels are disabled.
1107              * This level {@linkplain #getSeverity() severity} is
1108              * {@link Integer#MAX_VALUE}.
1109              */
1110             OFF(Integer.MAX_VALUE);  // typically mapped to/from j.u.l.Level.OFF
1111 
1112             private final int severity;
1113 
1114             private Level(int severity) {
1115                 this.severity = severity;
1116             }
1117 
1118             /**
1119              * Returns the name of this level.
1120              * @return this level {@linkplain #name()}.
1121              */
1122             public final String getName() {
1123                 return name();
1124             }
1125 
1126             /**
1127              * Returns the severity of this level.
1128              * A higher severity means a more severe condition.
1129              * @return this level severity.
1130              */
1131             public final int getSeverity() {
1132                 return severity;
1133             }
1134         }
1135 
1136         /**
1137          * Returns the name of this logger.
1138          *
1139          * @return the logger name.
1140          */
1141         public String getName();
1142 
1143         /**
1144          * Checks if a message of the given level would be logged by
1145          * this logger.
1146          *
1147          * @param level the log message level.
1148          * @return {@code true} if the given log message level is currently
1149          *         being logged.
1150          *
1151          * @throws NullPointerException if {@code level} is {@code null}.
1152          */
1153         public boolean isLoggable(Level level);
1154 
1155         /**
1156          * Logs a message.
1157          *
1158          * @implSpec The default implementation for this method calls
1159          * {@code this.log(level, (ResourceBundle)null, msg, (Object[])null);}
1160          *
1161          * @param level the log message level.
1162          * @param msg the string message (or a key in the message catalog, if
1163          * this logger is a {@link
1164          * LoggerFinder#getLocalizedLogger(java.lang.String,
1165          * java.util.ResourceBundle, java.lang.Module) localized logger});
1166          * can be {@code null}.
1167          *
1168          * @throws NullPointerException if {@code level} is {@code null}.
1169          */
1170         public default void log(Level level, String msg) {
1171             log(level, (ResourceBundle) null, msg, (Object[]) null);
1172         }
1173 
1174         /**
1175          * Logs a lazily supplied message.
1176          * <p>
1177          * If the logger is currently enabled for the given log message level
1178          * then a message is logged that is the result produced by the
1179          * given supplier function.  Otherwise, the supplier is not operated on.
1180          *
1181          * @implSpec When logging is enabled for the given level, the default
1182          * implementation for this method calls
1183          * {@code this.log(level, (ResourceBundle)null, msgSupplier.get(), (Object[])null);}
1184          *
1185          * @param level the log message level.
1186          * @param msgSupplier a supplier function that produces a message.
1187          *
1188          * @throws NullPointerException if {@code level} is {@code null},
1189          *         or {@code msgSupplier} is {@code null}.
1190          */
1191         public default void log(Level level, Supplier<String> msgSupplier) {
1192             Objects.requireNonNull(msgSupplier);
1193             if (isLoggable(Objects.requireNonNull(level))) {
1194                 log(level, (ResourceBundle) null, msgSupplier.get(), (Object[]) null);
1195             }
1196         }
1197 
1198         /**
1199          * Logs a message produced from the given object.
1200          * <p>
1201          * If the logger is currently enabled for the given log message level then
1202          * a message is logged that, by default, is the result produced from
1203          * calling  toString on the given object.
1204          * Otherwise, the object is not operated on.
1205          *
1206          * @implSpec When logging is enabled for the given level, the default
1207          * implementation for this method calls
1208          * {@code this.log(level, (ResourceBundle)null, obj.toString(), (Object[])null);}
1209          *
1210          * @param level the log message level.
1211          * @param obj the object to log.
1212          *
1213          * @throws NullPointerException if {@code level} is {@code null}, or
1214          *         {@code obj} is {@code null}.
1215          */
1216         public default void log(Level level, Object obj) {
1217             Objects.requireNonNull(obj);
1218             if (isLoggable(Objects.requireNonNull(level))) {
1219                 this.log(level, (ResourceBundle) null, obj.toString(), (Object[]) null);
1220             }
1221         }
1222 
1223         /**
1224          * Logs a message associated with a given throwable.
1225          *
1226          * @implSpec The default implementation for this method calls
1227          * {@code this.log(level, (ResourceBundle)null, msg, thrown);}
1228          *
1229          * @param level the log message level.
1230          * @param msg the string message (or a key in the message catalog, if
1231          * this logger is a {@link
1232          * LoggerFinder#getLocalizedLogger(java.lang.String,
1233          * java.util.ResourceBundle, java.lang.Module) localized logger});
1234          * can be {@code null}.
1235          * @param thrown a {@code Throwable} associated with the log message;
1236          *        can be {@code null}.
1237          *
1238          * @throws NullPointerException if {@code level} is {@code null}.
1239          */
1240         public default void log(Level level, String msg, Throwable thrown) {
1241             this.log(level, null, msg, thrown);
1242         }
1243 
1244         /**
1245          * Logs a lazily supplied message associated with a given throwable.
1246          * <p>
1247          * If the logger is currently enabled for the given log message level
1248          * then a message is logged that is the result produced by the
1249          * given supplier function.  Otherwise, the supplier is not operated on.
1250          *
1251          * @implSpec When logging is enabled for the given level, the default
1252          * implementation for this method calls
1253          * {@code this.log(level, (ResourceBundle)null, msgSupplier.get(), thrown);}
1254          *
1255          * @param level one of the log message level identifiers.
1256          * @param msgSupplier a supplier function that produces a message.
1257          * @param thrown a {@code Throwable} associated with log message;
1258          *               can be {@code null}.
1259          *
1260          * @throws NullPointerException if {@code level} is {@code null}, or
1261          *                               {@code msgSupplier} is {@code null}.
1262          */
1263         public default void log(Level level, Supplier<String> msgSupplier,
1264                 Throwable thrown) {
1265             Objects.requireNonNull(msgSupplier);
1266             if (isLoggable(Objects.requireNonNull(level))) {
1267                 this.log(level, null, msgSupplier.get(), thrown);
1268             }
1269         }
1270 
1271         /**
1272          * Logs a message with an optional list of parameters.
1273          *
1274          * @implSpec The default implementation for this method calls
1275          * {@code this.log(level, (ResourceBundle)null, format, params);}
1276          *
1277          * @param level one of the log message level identifiers.
1278          * @param format the string message format in {@link
1279          * java.text.MessageFormat} format, (or a key in the message
1280          * catalog, if this logger is a {@link
1281          * LoggerFinder#getLocalizedLogger(java.lang.String,
1282          * java.util.ResourceBundle, java.lang.Module) localized logger});
1283          * can be {@code null}.
1284          * @param params an optional list of parameters to the message (may be
1285          * none).
1286          *
1287          * @throws NullPointerException if {@code level} is {@code null}.
1288          */
1289         public default void log(Level level, String format, Object... params) {
1290             this.log(level, null, format, params);
1291         }
1292 
1293         /**
1294          * Logs a localized message associated with a given throwable.
1295          * <p>
1296          * If the given resource bundle is non-{@code null},  the {@code msg}
1297          * string is localized using the given resource bundle.
1298          * Otherwise the {@code msg} string is not localized.
1299          *
1300          * @param level the log message level.
1301          * @param bundle a resource bundle to localize {@code msg}; can be
1302          * {@code null}.
1303          * @param msg the string message (or a key in the message catalog,
1304          *            if {@code bundle} is not {@code null}); can be {@code null}.
1305          * @param thrown a {@code Throwable} associated with the log message;
1306          *        can be {@code null}.
1307          *
1308          * @throws NullPointerException if {@code level} is {@code null}.
1309          */
1310         public void log(Level level, ResourceBundle bundle, String msg,
1311                 Throwable thrown);
1312 
1313         /**
1314          * Logs a message with resource bundle and an optional list of
1315          * parameters.
1316          * <p>
1317          * If the given resource bundle is non-{@code null},  the {@code format}
1318          * string is localized using the given resource bundle.
1319          * Otherwise the {@code format} string is not localized.
1320          *
1321          * @param level the log message level.
1322          * @param bundle a resource bundle to localize {@code format}; can be
1323          * {@code null}.
1324          * @param format the string message format in {@link
1325          * java.text.MessageFormat} format, (or a key in the message
1326          * catalog if {@code bundle} is not {@code null}); can be {@code null}.
1327          * @param params an optional list of parameters to the message (may be
1328          * none).
1329          *
1330          * @throws NullPointerException if {@code level} is {@code null}.
1331          */
1332         public void log(Level level, ResourceBundle bundle, String format,
1333                 Object... params);
1334 
1335 
1336     }
1337 
1338     /**
1339      * The {@code LoggerFinder} service is responsible for creating, managing,
1340      * and configuring loggers to the underlying framework it uses.
1341      * <p>
1342      * A logger finder is a concrete implementation of this class that has a
1343      * zero-argument constructor and implements the abstract methods defined
1344      * by this class.
1345      * The loggers returned from a logger finder are capable of routing log
1346      * messages to the logging backend this provider supports.
1347      * A given invocation of the Java Runtime maintains a single
1348      * system-wide LoggerFinder instance that is loaded as follows:
1349      * <ul>
1350      *    <li>First it finds any custom {@code LoggerFinder} provider
1351      *        using the {@link java.util.ServiceLoader} facility with the
1352      *        {@linkplain ClassLoader#getSystemClassLoader() system class
1353      *        loader}.</li>
1354      *    <li>If no {@code LoggerFinder} provider is found, the system default
1355      *        {@code LoggerFinder} implementation will be used.</li>
1356      * </ul>
1357      * <p>
1358      * An application can replace the logging backend
1359      * <i>even when the java.logging module is present</i>, by simply providing
1360      * and declaring an implementation of the {@link LoggerFinder} service.
1361      * <p>
1362      * <b>Default Implementation</b>
1363      * <p>
1364      * The system default {@code LoggerFinder} implementation uses
1365      * {@code java.util.logging} as the backend framework when the
1366      * {@code java.logging} module is present.
1367      * It returns a {@linkplain System.Logger logger} instance
1368      * that will route log messages to a {@link java.util.logging.Logger
1369      * java.util.logging.Logger}. Otherwise, if {@code java.logging} is not
1370      * present, the default implementation will return a simple logger
1371      * instance that will route log messages of {@code INFO} level and above to
1372      * the console ({@code System.err}).
1373      * <p>
1374      * <b>Logging Configuration</b>
1375      * <p>
1376      * {@linkplain Logger Logger} instances obtained from the
1377      * {@code LoggerFinder} factory methods are not directly configurable by
1378      * the application. Configuration is the responsibility of the underlying
1379      * logging backend, and usually requires using APIs specific to that backend.
1380      * <p>For the default {@code LoggerFinder} implementation
1381      * using {@code java.util.logging} as its backend, refer to
1382      * {@link java.util.logging java.util.logging} for logging configuration.
1383      * For the default {@code LoggerFinder} implementation returning simple loggers
1384      * when the {@code java.logging} module is absent, the configuration
1385      * is implementation dependent.
1386      * <p>
1387      * Usually an application that uses a logging framework will log messages
1388      * through a logger facade defined (or supported) by that framework.
1389      * Applications that wish to use an external framework should log
1390      * through the facade associated with that framework.
1391      * <p>
1392      * A system class that needs to log messages will typically obtain
1393      * a {@link System.Logger} instance to route messages to the logging
1394      * framework selected by the application.
1395      * <p>
1396      * Libraries and classes that only need loggers to produce log messages
1397      * should not attempt to configure loggers by themselves, as that
1398      * would make them dependent from a specific implementation of the
1399      * {@code LoggerFinder} service.
1400      * <p>
1401      * In addition, when a security manager is present, loggers provided to
1402      * system classes should not be directly configurable through the logging
1403      * backend without requiring permissions.
1404      * <br>
1405      * It is the responsibility of the provider of
1406      * the concrete {@code LoggerFinder} implementation to ensure that
1407      * these loggers are not configured by untrusted code without proper
1408      * permission checks, as configuration performed on such loggers usually
1409      * affects all applications in the same Java Runtime.
1410      * <p>
1411      * <b>Message Levels and Mapping to backend levels</b>
1412      * <p>
1413      * A logger finder is responsible for mapping from a {@code
1414      * System.Logger.Level} to a level supported by the logging backend it uses.
1415      * <br>The default LoggerFinder using {@code java.util.logging} as the backend
1416      * maps {@code System.Logger} levels to
1417      * {@linkplain java.util.logging.Level java.util.logging} levels
1418      * of corresponding severity - as described in {@link Logger.Level
1419      * Logger.Level}.
1420      *
1421      * @see java.lang.System
1422      * @see java.lang.System.Logger
1423      *
1424      * @since 9
1425      */
1426     public static abstract class LoggerFinder {
1427         /**
1428          * The {@code RuntimePermission("loggerFinder")} is
1429          * necessary to subclass and instantiate the {@code LoggerFinder} class,
1430          * as well as to obtain loggers from an instance of that class.
1431          */
1432         static final RuntimePermission LOGGERFINDER_PERMISSION =
1433                 new RuntimePermission("loggerFinder");
1434 
1435         /**
1436          * Creates a new instance of {@code LoggerFinder}.
1437          *
1438          * @implNote It is recommended that a {@code LoggerFinder} service
1439          *   implementation does not perform any heavy initialization in its
1440          *   constructor, in order to avoid possible risks of deadlock or class
1441          *   loading cycles during the instantiation of the service provider.
1442          *
1443          * @throws SecurityException if a security manager is present and its
1444          *         {@code checkPermission} method doesn't allow the
1445          *         {@code RuntimePermission("loggerFinder")}.
1446          */
1447         protected LoggerFinder() {
1448             this(checkPermission());
1449         }
1450 
1451         private LoggerFinder(Void unused) {
1452             // nothing to do.
1453         }
1454 
1455         private static Void checkPermission() {
1456             final SecurityManager sm = System.getSecurityManager();
1457             if (sm != null) {
1458                 sm.checkPermission(LOGGERFINDER_PERMISSION);
1459             }
1460             return null;
1461         }
1462 
1463         /**
1464          * Returns an instance of {@link Logger Logger}
1465          * for the given {@code module}.
1466          *
1467          * @param name the name of the logger.
1468          * @param module the module for which the logger is being requested.
1469          *
1470          * @return a {@link Logger logger} suitable for use within the given
1471          *         module.
1472          * @throws NullPointerException if {@code name} is {@code null} or
1473          *        {@code module} is {@code null}.
1474          * @throws SecurityException if a security manager is present and its
1475          *         {@code checkPermission} method doesn't allow the
1476          *         {@code RuntimePermission("loggerFinder")}.
1477          */
1478         public abstract Logger getLogger(String name, Module module);
1479 
1480         /**
1481          * Returns a localizable instance of {@link Logger Logger}
1482          * for the given {@code module}.
1483          * The returned logger will use the provided resource bundle for
1484          * message localization.
1485          *
1486          * @implSpec By default, this method calls {@link
1487          * #getLogger(java.lang.String, java.lang.Module)
1488          * this.getLogger(name, module)} to obtain a logger, then wraps that
1489          * logger in a {@link Logger} instance where all methods that do not
1490          * take a {@link ResourceBundle} as parameter are redirected to one
1491          * which does - passing the given {@code bundle} for
1492          * localization. So for instance, a call to {@link
1493          * Logger#log(Level, String) Logger.log(Level.INFO, msg)}
1494          * will end up as a call to {@link
1495          * Logger#log(Level, ResourceBundle, String, Object...)
1496          * Logger.log(Level.INFO, bundle, msg, (Object[])null)} on the wrapped
1497          * logger instance.
1498          * Note however that by default, string messages returned by {@link
1499          * java.util.function.Supplier Supplier&lt;String&gt;} will not be
1500          * localized, as it is assumed that such strings are messages which are
1501          * already constructed, rather than keys in a resource bundle.
1502          * <p>
1503          * An implementation of {@code LoggerFinder} may override this method,
1504          * for example, when the underlying logging backend provides its own
1505          * mechanism for localizing log messages, then such a
1506          * {@code LoggerFinder} would be free to return a logger
1507          * that makes direct use of the mechanism provided by the backend.
1508          *
1509          * @param name    the name of the logger.
1510          * @param bundle  a resource bundle; can be {@code null}.
1511          * @param module  the module for which the logger is being requested.
1512          * @return an instance of {@link Logger Logger}  which will use the
1513          * provided resource bundle for message localization.
1514          *
1515          * @throws NullPointerException if {@code name} is {@code null} or
1516          *         {@code module} is {@code null}.
1517          * @throws SecurityException if a security manager is present and its
1518          *         {@code checkPermission} method doesn't allow the
1519          *         {@code RuntimePermission("loggerFinder")}.
1520          */
1521         public Logger getLocalizedLogger(String name, ResourceBundle bundle,
1522                                          Module module) {
1523             return new LocalizedLoggerWrapper<>(getLogger(name, module), bundle);
1524         }
1525 
1526         /**
1527          * Returns the {@code LoggerFinder} instance. There is one
1528          * single system-wide {@code LoggerFinder} instance in
1529          * the Java Runtime.  See the class specification of how the
1530          * {@link LoggerFinder LoggerFinder} implementation is located and
1531          * loaded.
1532 
1533          * @return the {@link LoggerFinder LoggerFinder} instance.
1534          * @throws SecurityException if a security manager is present and its
1535          *         {@code checkPermission} method doesn't allow the
1536          *         {@code RuntimePermission("loggerFinder")}.
1537          */
1538         public static LoggerFinder getLoggerFinder() {
1539             final SecurityManager sm = System.getSecurityManager();
1540             if (sm != null) {
1541                 sm.checkPermission(LOGGERFINDER_PERMISSION);
1542             }
1543             return accessProvider();
1544         }
1545 
1546 
1547         private static volatile LoggerFinder service;
1548         static LoggerFinder accessProvider() {
1549             // We do not need to synchronize: LoggerFinderLoader will
1550             // always return the same instance, so if we don't have it,
1551             // just fetch it again.
1552             if (service == null) {
1553                 PrivilegedAction<LoggerFinder> pa =
1554                         () -> LoggerFinderLoader.getLoggerFinder();
1555                 service = AccessController.doPrivileged(pa, null,
1556                         LOGGERFINDER_PERMISSION);
1557             }
1558             return service;
1559         }
1560 
1561     }
1562 
1563 
1564     /**
1565      * Returns an instance of {@link Logger Logger} for the caller's
1566      * use.
1567      *
1568      * @implSpec
1569      * Instances returned by this method route messages to loggers
1570      * obtained by calling {@link LoggerFinder#getLogger(java.lang.String,
1571      * java.lang.Module) LoggerFinder.getLogger(name, module)}, where
1572      * {@code module} is the caller's module.
1573      * In cases where {@code System.getLogger} is called from a context where
1574      * there is no caller frame on the stack (e.g when called directly
1575      * from a JNI attached thread), {@code IllegalCallerException} is thrown.
1576      * To obtain a logger in such a context, use an auxiliary class that will
1577      * implicitly be identified as the caller, or use the system {@link
1578      * LoggerFinder#getLoggerFinder() LoggerFinder} to obtain a logger instead.
1579      * Note that doing the latter may eagerly initialize the underlying
1580      * logging system.
1581      *
1582      * @apiNote
1583      * This method may defer calling the {@link
1584      * LoggerFinder#getLogger(java.lang.String, java.lang.Module)
1585      * LoggerFinder.getLogger} method to create an actual logger supplied by
1586      * the logging backend, for instance, to allow loggers to be obtained during
1587      * the system initialization time.
1588      *
1589      * @param name the name of the logger.
1590      * @return an instance of {@link Logger} that can be used by the calling
1591      *         class.
1592      * @throws NullPointerException if {@code name} is {@code null}.
1593      * @throws IllegalCallerException if there is no Java caller frame on the
1594      *         stack.
1595      *
1596      * @since 9
1597      */
1598     @CallerSensitive
1599     public static Logger getLogger(String name) {
1600         Objects.requireNonNull(name);
1601         final Class<?> caller = Reflection.getCallerClass();
1602         if (caller == null) {
1603             throw new IllegalCallerException("no caller frame");
1604         }
1605         return LazyLoggers.getLogger(name, caller.getModule());
1606     }
1607 
1608     /**
1609      * Returns a localizable instance of {@link Logger
1610      * Logger} for the caller's use.
1611      * The returned logger will use the provided resource bundle for message
1612      * localization.
1613      *
1614      * @implSpec
1615      * The returned logger will perform message localization as specified
1616      * by {@link LoggerFinder#getLocalizedLogger(java.lang.String,
1617      * java.util.ResourceBundle, java.lang.Module)
1618      * LoggerFinder.getLocalizedLogger(name, bundle, module)}, where
1619      * {@code module} is the caller's module.
1620      * In cases where {@code System.getLogger} is called from a context where
1621      * there is no caller frame on the stack (e.g when called directly
1622      * from a JNI attached thread), {@code IllegalCallerException} is thrown.
1623      * To obtain a logger in such a context, use an auxiliary class that
1624      * will implicitly be identified as the caller, or use the system {@link
1625      * LoggerFinder#getLoggerFinder() LoggerFinder} to obtain a logger instead.
1626      * Note that doing the latter may eagerly initialize the underlying
1627      * logging system.
1628      *
1629      * @apiNote
1630      * This method is intended to be used after the system is fully initialized.
1631      * This method may trigger the immediate loading and initialization
1632      * of the {@link LoggerFinder} service, which may cause issues if the
1633      * Java Runtime is not ready to initialize the concrete service
1634      * implementation yet.
1635      * System classes which may be loaded early in the boot sequence and
1636      * need to log localized messages should create a logger using
1637      * {@link #getLogger(java.lang.String)} and then use the log methods that
1638      * take a resource bundle as parameter.
1639      *
1640      * @param name    the name of the logger.
1641      * @param bundle  a resource bundle.
1642      * @return an instance of {@link Logger} which will use the provided
1643      * resource bundle for message localization.
1644      * @throws NullPointerException if {@code name} is {@code null} or
1645      *         {@code bundle} is {@code null}.
1646      * @throws IllegalCallerException if there is no Java caller frame on the
1647      *         stack.
1648      *
1649      * @since 9
1650      */
1651     @CallerSensitive
1652     public static Logger getLogger(String name, ResourceBundle bundle) {
1653         final ResourceBundle rb = Objects.requireNonNull(bundle);
1654         Objects.requireNonNull(name);
1655         final Class<?> caller = Reflection.getCallerClass();
1656         if (caller == null) {
1657             throw new IllegalCallerException("no caller frame");
1658         }
1659         final SecurityManager sm = System.getSecurityManager();
1660         // We don't use LazyLoggers if a resource bundle is specified.
1661         // Bootstrap sensitive classes in the JDK do not use resource bundles
1662         // when logging. This could be revisited later, if it needs to.
1663         if (sm != null) {
1664             final PrivilegedAction<Logger> pa =
1665                     () -> LoggerFinder.accessProvider()
1666                             .getLocalizedLogger(name, rb, caller.getModule());
1667             return AccessController.doPrivileged(pa, null,
1668                                          LoggerFinder.LOGGERFINDER_PERMISSION);
1669         }
1670         return LoggerFinder.accessProvider()
1671                 .getLocalizedLogger(name, rb, caller.getModule());
1672     }
1673 
1674     /**
1675      * Terminates the currently running Java Virtual Machine. The
1676      * argument serves as a status code; by convention, a nonzero status
1677      * code indicates abnormal termination.
1678      * <p>
1679      * This method calls the <code>exit</code> method in class
1680      * <code>Runtime</code>. This method never returns normally.
1681      * <p>
1682      * The call <code>System.exit(n)</code> is effectively equivalent to
1683      * the call:
1684      * <blockquote><pre>
1685      * Runtime.getRuntime().exit(n)
1686      * </pre></blockquote>
1687      *
1688      * @param      status   exit status.
1689      * @throws  SecurityException
1690      *        if a security manager exists and its <code>checkExit</code>
1691      *        method doesn't allow exit with the specified status.
1692      * @see        java.lang.Runtime#exit(int)
1693      */
1694     public static void exit(int status) {
1695         Runtime.getRuntime().exit(status);
1696     }
1697 
1698     /**
1699      * Runs the garbage collector.
1700      * <p>
1701      * Calling the <code>gc</code> method suggests that the Java Virtual
1702      * Machine expend effort toward recycling unused objects in order to
1703      * make the memory they currently occupy available for quick reuse.
1704      * When control returns from the method call, the Java Virtual
1705      * Machine has made a best effort to reclaim space from all discarded
1706      * objects.
1707      * <p>
1708      * The call <code>System.gc()</code> is effectively equivalent to the
1709      * call:
1710      * <blockquote><pre>
1711      * Runtime.getRuntime().gc()
1712      * </pre></blockquote>
1713      *
1714      * @see     java.lang.Runtime#gc()
1715      */
1716     public static void gc() {
1717         Runtime.getRuntime().gc();
1718     }
1719 
1720     /**
1721      * Runs the finalization methods of any objects pending finalization.
1722      * <p>
1723      * Calling this method suggests that the Java Virtual Machine expend
1724      * effort toward running the <code>finalize</code> methods of objects
1725      * that have been found to be discarded but whose <code>finalize</code>
1726      * methods have not yet been run. When control returns from the
1727      * method call, the Java Virtual Machine has made a best effort to
1728      * complete all outstanding finalizations.
1729      * <p>
1730      * The call <code>System.runFinalization()</code> is effectively
1731      * equivalent to the call:
1732      * <blockquote><pre>
1733      * Runtime.getRuntime().runFinalization()
1734      * </pre></blockquote>
1735      *
1736      * @see     java.lang.Runtime#runFinalization()
1737      */
1738     public static void runFinalization() {
1739         Runtime.getRuntime().runFinalization();
1740     }
1741 
1742     /**
1743      * Enable or disable finalization on exit; doing so specifies that the
1744      * finalizers of all objects that have finalizers that have not yet been
1745      * automatically invoked are to be run before the Java runtime exits.
1746      * By default, finalization on exit is disabled.
1747      *
1748      * <p>If there is a security manager,
1749      * its <code>checkExit</code> method is first called
1750      * with 0 as its argument to ensure the exit is allowed.
1751      * This could result in a SecurityException.
1752      *
1753      * @deprecated  This method is inherently unsafe.  It may result in
1754      *      finalizers being called on live objects while other threads are
1755      *      concurrently manipulating those objects, resulting in erratic
1756      *      behavior or deadlock.
1757      *      This method is subject to removal in a future version of Java SE.
1758      * @param value indicating enabling or disabling of finalization
1759      * @throws  SecurityException
1760      *        if a security manager exists and its <code>checkExit</code>
1761      *        method doesn't allow the exit.
1762      *
1763      * @see     java.lang.Runtime#exit(int)
1764      * @see     java.lang.Runtime#gc()
1765      * @see     java.lang.SecurityManager#checkExit(int)
1766      * @since   1.1
1767      */
1768     @Deprecated(since="1.2", forRemoval=true)
1769     @SuppressWarnings("removal")
1770     public static void runFinalizersOnExit(boolean value) {
1771         Runtime.runFinalizersOnExit(value);
1772     }
1773 
1774     /**
1775      * Loads the native library specified by the filename argument.  The filename
1776      * argument must be an absolute path name.
1777      *
1778      * If the filename argument, when stripped of any platform-specific library
1779      * prefix, path, and file extension, indicates a library whose name is,
1780      * for example, L, and a native library called L is statically linked
1781      * with the VM, then the JNI_OnLoad_L function exported by the library
1782      * is invoked rather than attempting to load a dynamic library.
1783      * A filename matching the argument does not have to exist in the
1784      * file system.
1785      * See the JNI Specification for more details.
1786      *
1787      * Otherwise, the filename argument is mapped to a native library image in
1788      * an implementation-dependent manner.
1789      *
1790      * <p>
1791      * The call <code>System.load(name)</code> is effectively equivalent
1792      * to the call:
1793      * <blockquote><pre>
1794      * Runtime.getRuntime().load(name)
1795      * </pre></blockquote>
1796      *
1797      * @param      filename   the file to load.
1798      * @exception  SecurityException  if a security manager exists and its
1799      *             <code>checkLink</code> method doesn't allow
1800      *             loading of the specified dynamic library
1801      * @exception  UnsatisfiedLinkError  if either the filename is not an
1802      *             absolute path name, the native library is not statically
1803      *             linked with the VM, or the library cannot be mapped to
1804      *             a native library image by the host system.
1805      * @exception  NullPointerException if <code>filename</code> is
1806      *             <code>null</code>
1807      * @see        java.lang.Runtime#load(java.lang.String)
1808      * @see        java.lang.SecurityManager#checkLink(java.lang.String)
1809      */
1810     @CallerSensitive
1811     public static void load(String filename) {
1812         Runtime.getRuntime().load0(Reflection.getCallerClass(), filename);
1813     }
1814 
1815     /**
1816      * Loads the native library specified by the <code>libname</code>
1817      * argument.  The <code>libname</code> argument must not contain any platform
1818      * specific prefix, file extension or path. If a native library
1819      * called <code>libname</code> is statically linked with the VM, then the
1820      * JNI_OnLoad_<code>libname</code> function exported by the library is invoked.
1821      * See the JNI Specification for more details.
1822      *
1823      * Otherwise, the libname argument is loaded from a system library
1824      * location and mapped to a native library image in an implementation-
1825      * dependent manner.
1826      * <p>
1827      * The call <code>System.loadLibrary(name)</code> is effectively
1828      * equivalent to the call
1829      * <blockquote><pre>
1830      * Runtime.getRuntime().loadLibrary(name)
1831      * </pre></blockquote>
1832      *
1833      * @param      libname   the name of the library.
1834      * @exception  SecurityException  if a security manager exists and its
1835      *             <code>checkLink</code> method doesn't allow
1836      *             loading of the specified dynamic library
1837      * @exception  UnsatisfiedLinkError if either the libname argument
1838      *             contains a file path, the native library is not statically
1839      *             linked with the VM,  or the library cannot be mapped to a
1840      *             native library image by the host system.
1841      * @exception  NullPointerException if <code>libname</code> is
1842      *             <code>null</code>
1843      * @see        java.lang.Runtime#loadLibrary(java.lang.String)
1844      * @see        java.lang.SecurityManager#checkLink(java.lang.String)
1845      */
1846     @CallerSensitive
1847     public static void loadLibrary(String libname) {
1848         Runtime.getRuntime().loadLibrary0(Reflection.getCallerClass(), libname);
1849     }
1850 
1851     /**
1852      * Maps a library name into a platform-specific string representing
1853      * a native library.
1854      *
1855      * @param      libname the name of the library.
1856      * @return     a platform-dependent native library name.
1857      * @exception  NullPointerException if <code>libname</code> is
1858      *             <code>null</code>
1859      * @see        java.lang.System#loadLibrary(java.lang.String)
1860      * @see        java.lang.ClassLoader#findLibrary(java.lang.String)
1861      * @since      1.2
1862      */
1863     public static native String mapLibraryName(String libname);
1864 
1865     /**
1866      * Create PrintStream for stdout/err based on encoding.
1867      */
1868     private static PrintStream newPrintStream(FileOutputStream fos, String enc) {
1869        if (enc != null) {
1870             try {
1871                 return new PrintStream(new BufferedOutputStream(fos, 128), true, enc);
1872             } catch (UnsupportedEncodingException uee) {}
1873         }
1874         return new PrintStream(new BufferedOutputStream(fos, 128), true);
1875     }
1876 
1877     /**
1878      * Logs an exception/error at initialization time to stdout or stderr.
1879      *
1880      * @param printToStderr to print to stderr rather than stdout
1881      * @param printStackTrace to print the stack trace
1882      * @param msg the message to print before the exception, can be {@code null}
1883      * @param e the exception or error
1884      */
1885     private static void logInitException(boolean printToStderr,
1886                                          boolean printStackTrace,
1887                                          String msg,
1888                                          Throwable e) {
1889         if (VM.initLevel() < 1) {
1890             throw new InternalError("system classes not initialized");
1891         }
1892         PrintStream log = (printToStderr) ? err : out;
1893         if (msg != null) {
1894             log.println(msg);
1895         }
1896         if (printStackTrace) {
1897             e.printStackTrace(log);
1898         } else {
1899             log.println(e);
1900             for (Throwable suppressed : e.getSuppressed()) {
1901                 log.println("Suppressed: " + suppressed);
1902             }
1903             Throwable cause = e.getCause();
1904             if (cause != null) {
1905                 log.println("Caused by: " + cause);
1906             }
1907         }
1908     }
1909 
1910     /**
1911      * Initialize the system class.  Called after thread initialization.
1912      */
1913     private static void initPhase1() {
1914 
1915         // VM might invoke JNU_NewStringPlatform() to set those encoding
1916         // sensitive properties (user.home, user.name, boot.class.path, etc.)
1917         // during "props" initialization, in which it may need access, via
1918         // System.getProperty(), to the related system encoding property that
1919         // have been initialized (put into "props") at early stage of the
1920         // initialization. So make sure the "props" is available at the
1921         // very beginning of the initialization and all system properties to
1922         // be put into it directly.
1923         props = new Properties();
1924         initProperties(props);  // initialized by the VM
1925 
1926         // There are certain system configurations that may be controlled by
1927         // VM options such as the maximum amount of direct memory and
1928         // Integer cache size used to support the object identity semantics
1929         // of autoboxing.  Typically, the library will obtain these values
1930         // from the properties set by the VM.  If the properties are for
1931         // internal implementation use only, these properties should be
1932         // removed from the system properties.
1933         //
1934         // See java.lang.Integer.IntegerCache and the
1935         // VM.saveAndRemoveProperties method for example.
1936         //
1937         // Save a private copy of the system properties object that
1938         // can only be accessed by the internal implementation.  Remove
1939         // certain system properties that are not intended for public access.
1940         VM.saveAndRemoveProperties(props);
1941 
1942         lineSeparator = props.getProperty("line.separator");
1943         VersionProps.init();
1944 
1945         FileInputStream fdIn = new FileInputStream(FileDescriptor.in);
1946         FileOutputStream fdOut = new FileOutputStream(FileDescriptor.out);
1947         FileOutputStream fdErr = new FileOutputStream(FileDescriptor.err);
1948         setIn0(new BufferedInputStream(fdIn));
1949         setOut0(newPrintStream(fdOut, props.getProperty("sun.stdout.encoding")));
1950         setErr0(newPrintStream(fdErr, props.getProperty("sun.stderr.encoding")));
1951 
1952         // Load the zip library now in order to keep java.util.zip.ZipFile
1953         // from trying to use itself to load this library later.
1954         loadLibrary("zip");
1955 
1956         // Setup Java signal handlers for HUP, TERM, and INT (where available).
1957         Terminator.setup();
1958 
1959         // Initialize any miscellaneous operating system settings that need to be
1960         // set for the class libraries. Currently this is no-op everywhere except
1961         // for Windows where the process-wide error mode is set before the java.io
1962         // classes are used.
1963         VM.initializeOSEnvironment();
1964 
1965         // The main thread is not added to its thread group in the same
1966         // way as other threads; we must do it ourselves here.
1967         Thread current = Thread.currentThread();
1968         current.getThreadGroup().add(current);
1969 
1970         // register shared secrets
1971         setJavaLangAccess();
1972 
1973         // Subsystems that are invoked during initialization can invoke
1974         // VM.isBooted() in order to avoid doing things that should
1975         // wait until the VM is fully initialized. The initialization level
1976         // is incremented from 0 to 1 here to indicate the first phase of
1977         // initialization has completed.
1978         // IMPORTANT: Ensure that this remains the last initialization action!
1979         VM.initLevel(1);
1980     }
1981 
1982     // @see #initPhase2()
1983     static ModuleLayer bootLayer;
1984 
1985     /*
1986      * Invoked by VM.  Phase 2 module system initialization.
1987      * Only classes in java.base can be loaded in this phase.
1988      *
1989      * @param printToStderr print exceptions to stderr rather than stdout
1990      * @param printStackTrace print stack trace when exception occurs
1991      *
1992      * @return JNI_OK for success, JNI_ERR for failure
1993      */
1994     private static int initPhase2(boolean printToStderr, boolean printStackTrace) {
1995         try {
1996             bootLayer = ModuleBootstrap.boot();
1997         } catch (Exception | Error e) {
1998             logInitException(printToStderr, printStackTrace,
1999                              "Error occurred during initialization of boot layer", e);
2000             return -1; // JNI_ERR
2001         }
2002 
2003         // module system initialized
2004         VM.initLevel(2);
2005 
2006         return 0; // JNI_OK
2007     }
2008 
2009     /*
2010      * Invoked by VM.  Phase 3 is the final system initialization:
2011      * 1. set security manager
2012      * 2. set system class loader
2013      * 3. set TCCL
2014      *
2015      * This method must be called after the module system initialization.
2016      * The security manager and system class loader may be custom class from
2017      * the application classpath or modulepath.
2018      */
2019     private static void initPhase3() {
2020         // set security manager
2021         String cn = System.getProperty("java.security.manager");
2022         if (cn != null) {
2023             if (cn.isEmpty() || "default".equals(cn)) {
2024                 System.setSecurityManager(new SecurityManager());
2025             } else {
2026                 try {
2027                     Class<?> c = Class.forName(cn, false, ClassLoader.getBuiltinAppClassLoader());
2028                     Constructor<?> ctor = c.getConstructor();
2029                     // Must be a public subclass of SecurityManager with
2030                     // a public no-arg constructor
2031                     if (!SecurityManager.class.isAssignableFrom(c) ||
2032                             !Modifier.isPublic(c.getModifiers()) ||
2033                             !Modifier.isPublic(ctor.getModifiers())) {
2034                         throw new Error("Could not create SecurityManager: " + ctor.toString());
2035                     }
2036                     // custom security manager implementation may be in unnamed module
2037                     // or a named module but non-exported package
2038                     ctor.setAccessible(true);
2039                     SecurityManager sm = (SecurityManager) ctor.newInstance();
2040                     System.setSecurityManager(sm);
2041                 } catch (Exception e) {
2042                     throw new Error("Could not create SecurityManager", e);
2043                 }
2044             }
2045         }
2046 
2047         // initializing the system class loader
2048         VM.initLevel(3);
2049 
2050         // system class loader initialized
2051         ClassLoader scl = ClassLoader.initSystemClassLoader();
2052 
2053         // set TCCL
2054         Thread.currentThread().setContextClassLoader(scl);
2055 
2056         // system is fully initialized
2057         VM.initLevel(4);
2058     }
2059 
2060     private static void setJavaLangAccess() {
2061         // Allow privileged classes outside of java.lang
2062         SharedSecrets.setJavaLangAccess(new JavaLangAccess() {
2063             public Method getMethodOrNull(Class<?> klass, String name, Class<?>... parameterTypes) {
2064                 return klass.getMethodOrNull(name, parameterTypes);
2065             }
2066             public jdk.internal.reflect.ConstantPool getConstantPool(Class<?> klass) {
2067                 return klass.getConstantPool();
2068             }
2069             public boolean casAnnotationType(Class<?> klass, AnnotationType oldType, AnnotationType newType) {
2070                 return klass.casAnnotationType(oldType, newType);
2071             }
2072             public AnnotationType getAnnotationType(Class<?> klass) {
2073                 return klass.getAnnotationType();
2074             }
2075             public Map<Class<? extends Annotation>, Annotation> getDeclaredAnnotationMap(Class<?> klass) {
2076                 return klass.getDeclaredAnnotationMap();
2077             }
2078             public byte[] getRawClassAnnotations(Class<?> klass) {
2079                 return klass.getRawAnnotations();
2080             }
2081             public byte[] getRawClassTypeAnnotations(Class<?> klass) {
2082                 return klass.getRawTypeAnnotations();
2083             }
2084             public byte[] getRawExecutableTypeAnnotations(Executable executable) {
2085                 return Class.getExecutableTypeAnnotationBytes(executable);
2086             }
2087             public <E extends Enum<E>>
2088                     E[] getEnumConstantsShared(Class<E> klass) {
2089                 return klass.getEnumConstantsShared();
2090             }
2091             public void blockedOn(Thread t, Interruptible b) {
2092                 t.blockedOn(b);
2093             }
2094             public void registerShutdownHook(int slot, boolean registerShutdownInProgress, Runnable hook) {
2095                 Shutdown.add(slot, registerShutdownInProgress, hook);
2096             }
2097             public String newStringUnsafe(char[] chars) {
2098                 return new String(chars, true);
2099             }
2100             public Thread newThreadWithAcc(Runnable target, AccessControlContext acc) {
2101                 return new Thread(target, acc);
2102             }
2103             @SuppressWarnings("deprecation")
2104             public void invokeFinalize(Object o) throws Throwable {
2105                 o.finalize();
2106             }
2107             public ConcurrentHashMap<?, ?> createOrGetClassLoaderValueMap(ClassLoader cl) {
2108                 return cl.createOrGetClassLoaderValueMap();
2109             }
2110             public Class<?> defineClass(ClassLoader loader, String name, byte[] b, ProtectionDomain pd, String source) {
2111                 return ClassLoader.defineClass1(loader, name, b, 0, b.length, pd, source);
2112             }
2113             public Class<?> findBootstrapClassOrNull(ClassLoader cl, String name) {
2114                 return cl.findBootstrapClassOrNull(name);
2115             }
2116             public Stream<Package> packages(ClassLoader cl) {
2117                 return cl.packages();
2118             }
2119             public Package definePackage(ClassLoader cl, String name, Module module) {
2120                 return cl.definePackage(name, module);
2121             }
2122             public String fastUUID(long lsb, long msb) {
2123                 return Long.fastUUID(lsb, msb);
2124             }
2125             public void addNonExportedPackages(ModuleLayer layer) {
2126                 SecurityManager.addNonExportedPackages(layer);
2127             }
2128             public void invalidatePackageAccessCache() {
2129                 SecurityManager.invalidatePackageAccessCache();
2130             }
2131             public Module defineModule(ClassLoader loader,
2132                                        ModuleDescriptor descriptor,
2133                                        URI uri) {
2134                 return new Module(null, loader, descriptor, uri);
2135             }
2136             public Module defineUnnamedModule(ClassLoader loader) {
2137                 return new Module(loader);
2138             }
2139             public void addReads(Module m1, Module m2) {
2140                 m1.implAddReads(m2);
2141             }
2142             public void addReadsAllUnnamed(Module m) {
2143                 m.implAddReadsAllUnnamed();
2144             }
2145             public void addExports(Module m, String pn, Module other) {
2146                 m.implAddExports(pn, other);
2147             }
2148             public void addExportsToAllUnnamed(Module m, String pn) {
2149                 m.implAddExportsToAllUnnamed(pn);
2150             }
2151             public void addOpens(Module m, String pn, Module other) {
2152                 m.implAddOpens(pn, other);
2153             }
2154             public void addOpensToAllUnnamed(Module m, String pn) {
2155                 m.implAddOpensToAllUnnamed(pn);
2156             }
2157             public void addUses(Module m, Class<?> service) {
2158                 m.implAddUses(service);
2159             }
2160             public ServicesCatalog getServicesCatalog(ModuleLayer layer) {
2161                 return layer.getServicesCatalog();
2162             }
2163             public Stream<ModuleLayer> layers(ModuleLayer layer) {
2164                 return layer.layers();
2165             }
2166             public Stream<ModuleLayer> layers(ClassLoader loader) {
2167                 return ModuleLayer.layers(loader);
2168             }
2169             public Class<?> loadValueTypeClass(Module module, ClassLoader cl, String name) {
2170                 try {
2171                     // VM support to define DVT
2172                     return Class.forName0(name, false, cl, Object.class);
2173                 } catch (ClassNotFoundException e) {
2174                     throw new InternalError(e);
2175                 }
2176             }
2177         });
2178     }
2179 }