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