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