1 /*
2 * Copyright (c) 1994, 2021, 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.invoke.MethodHandle;
39 import java.lang.invoke.MethodType;
40 import java.lang.invoke.StringConcatFactory;
41 import java.lang.module.ModuleDescriptor;
42 import java.lang.reflect.Constructor;
43 import java.lang.reflect.Executable;
44 import java.lang.reflect.Method;
45 import java.lang.reflect.Modifier;
46 import java.net.URI;
47 import java.net.URL;
48 import java.nio.charset.CharacterCodingException;
49 import java.nio.channels.Channel;
50 import java.nio.channels.spi.SelectorProvider;
51 import java.nio.charset.Charset;
52 import java.security.AccessControlContext;
53 import java.security.AccessController;
54 import java.security.CodeSource;
55 import java.security.PrivilegedAction;
56 import java.security.ProtectionDomain;
57 import java.util.Collections;
58 import java.util.List;
59 import java.util.Map;
60 import java.util.Objects;
61 import java.util.Properties;
62 import java.util.PropertyPermission;
63 import java.util.ResourceBundle;
64 import java.util.Set;
65 import java.util.WeakHashMap;
66 import java.util.function.Supplier;
67 import java.util.concurrent.ConcurrentHashMap;
68 import java.util.stream.Stream;
69 import jdk.internal.misc.Unsafe;
70 import jdk.internal.util.StaticProperty;
71 import jdk.internal.module.ModuleBootstrap;
72 import jdk.internal.module.ServicesCatalog;
73 import jdk.internal.reflect.CallerSensitive;
74 import jdk.internal.reflect.Reflection;
75 import jdk.internal.access.JavaLangAccess;
76 import jdk.internal.access.SharedSecrets;
77 import jdk.internal.misc.VM;
78 import jdk.internal.logger.LoggerFinderLoader;
79 import jdk.internal.logger.LazyLoggers;
80 import jdk.internal.logger.LocalizedLoggerWrapper;
81 import jdk.internal.util.SystemProps;
82 import jdk.internal.vm.annotation.IntrinsicCandidate;
83 import jdk.internal.vm.annotation.Stable;
84 import sun.nio.fs.DefaultFileSystemProvider;
85 import sun.reflect.annotation.AnnotationType;
86 import sun.nio.ch.Interruptible;
87 import sun.security.util.SecurityConstants;
88
89 /**
90 * The {@code System} class contains several useful class fields
91 * and methods. It cannot be instantiated.
92 *
93 * Among the facilities provided by the {@code System} class
94 * are standard input, standard output, and error output streams;
95 * access to externally defined properties and environment
96 * variables; a means of loading files and libraries; and a utility
97 * method for quickly copying a portion of an array.
98 *
99 * @since 1.0
100 */
101 public final class System {
102 /* Register the natives via the static initializer.
103 *
104 * The VM will invoke the initPhase1 method to complete the initialization
105 * of this class separate from <clinit>.
106 */
107 private static native void registerNatives();
108 static {
109 registerNatives();
110 }
111
112 /** Don't let anyone instantiate this class */
113 private System() {
114 }
115
116 /**
117 * The "standard" input stream. This stream is already
118 * open and ready to supply input data. Typically this stream
119 * corresponds to keyboard input or another input source specified by
120 * the host environment or user. In case this stream is wrapped
121 * in a {@link java.io.InputStreamReader}, {@link Console#charset()}
122 * should be used for the charset, or consider using
123 * {@link Console#reader()}.
124 *
125 * @see Console#charset()
126 * @see Console#reader()
127 */
128 public static final InputStream in = null;
129
130 /**
131 * The "standard" output stream. This stream is already
132 * open and ready to accept output data. Typically this stream
133 * corresponds to display output or another output destination
134 * specified by the host environment or user. The encoding used
135 * in the conversion from characters to bytes is equivalent to
136 * {@link Console#charset()} if the {@code Console} exists,
137 * {@link Charset#defaultCharset()} otherwise.
138 * <p>
139 * For simple stand-alone Java applications, a typical way to write
140 * a line of output data is:
141 * <blockquote><pre>
142 * System.out.println(data)
143 * </pre></blockquote>
144 * <p>
145 * See the {@code println} methods in class {@code PrintStream}.
146 *
147 * @see java.io.PrintStream#println()
148 * @see java.io.PrintStream#println(boolean)
149 * @see java.io.PrintStream#println(char)
150 * @see java.io.PrintStream#println(char[])
151 * @see java.io.PrintStream#println(double)
152 * @see java.io.PrintStream#println(float)
153 * @see java.io.PrintStream#println(int)
154 * @see java.io.PrintStream#println(long)
155 * @see java.io.PrintStream#println(java.lang.Object)
156 * @see java.io.PrintStream#println(java.lang.String)
157 * @see Console#charset()
158 * @see Charset#defaultCharset()
159 */
160 public static final PrintStream out = null;
161
162 /**
163 * The "standard" error output stream. This stream is already
164 * open and ready to accept output data.
165 * <p>
166 * Typically this stream corresponds to display output or another
167 * output destination specified by the host environment or user. By
168 * convention, this output stream is used to display error messages
169 * or other information that should come to the immediate attention
170 * of a user even if the principal output stream, the value of the
171 * variable {@code out}, has been redirected to a file or other
172 * destination that is typically not continuously monitored.
173 * The encoding used in the conversion from characters to bytes is
174 * equivalent to {@link Console#charset()} if the {@code Console}
175 * exists, {@link Charset#defaultCharset()} otherwise.
176 *
177 * @see Console#charset()
178 * @see Charset#defaultCharset()
179 */
180 public static final PrintStream err = null;
181
182 // indicates if a security manager is possible
183 private static final int NEVER = 1;
184 private static final int MAYBE = 2;
185 private static @Stable int allowSecurityManager;
186
187 // current security manager
188 @SuppressWarnings("removal")
189 private static volatile SecurityManager security; // read by VM
190
191 // return true if a security manager is allowed
192 private static boolean allowSecurityManager() {
193 return (allowSecurityManager != NEVER);
194 }
195
196 /**
197 * Reassigns the "standard" input stream.
198 *
199 * First, if there is a security manager, its {@code checkPermission}
200 * method is called with a {@code RuntimePermission("setIO")} permission
201 * to see if it's ok to reassign the "standard" input stream.
202 *
203 * @param in the new standard input stream.
204 *
205 * @throws SecurityException
206 * if a security manager exists and its
207 * {@code checkPermission} method doesn't allow
208 * reassigning of the standard input stream.
209 *
210 * @see SecurityManager#checkPermission
211 * @see java.lang.RuntimePermission
212 *
213 * @since 1.1
214 */
215 public static void setIn(InputStream in) {
216 checkIO();
217 setIn0(in);
218 }
219
220 /**
221 * Reassigns the "standard" output stream.
222 *
223 * First, if there is a security manager, its {@code checkPermission}
224 * method is called with a {@code RuntimePermission("setIO")} permission
225 * to see if it's ok to reassign the "standard" output stream.
226 *
227 * @param out the new standard output stream
228 *
229 * @throws SecurityException
230 * if a security manager exists and its
231 * {@code checkPermission} method doesn't allow
232 * reassigning of the standard output stream.
233 *
234 * @see SecurityManager#checkPermission
235 * @see java.lang.RuntimePermission
236 *
237 * @since 1.1
238 */
239 public static void setOut(PrintStream out) {
240 checkIO();
241 setOut0(out);
242 }
243
244 /**
245 * Reassigns the "standard" error output stream.
246 *
247 * First, if there is a security manager, its {@code checkPermission}
248 * method is called with a {@code RuntimePermission("setIO")} permission
249 * to see if it's ok to reassign the "standard" error output stream.
250 *
251 * @param err the new standard error output stream.
252 *
253 * @throws SecurityException
254 * if a security manager exists and its
255 * {@code checkPermission} method doesn't allow
256 * reassigning of the standard error output stream.
257 *
258 * @see SecurityManager#checkPermission
259 * @see java.lang.RuntimePermission
260 *
261 * @since 1.1
262 */
263 public static void setErr(PrintStream err) {
264 checkIO();
265 setErr0(err);
266 }
267
268 private static volatile Console cons;
269
270 /**
271 * Returns the unique {@link java.io.Console Console} object associated
272 * with the current Java virtual machine, if any.
273 *
274 * @return The system console, if any, otherwise {@code null}.
275 *
276 * @since 1.6
277 */
278 public static Console console() {
279 Console c;
280 if ((c = cons) == null) {
281 synchronized (System.class) {
282 if ((c = cons) == null) {
283 cons = c = SharedSecrets.getJavaIOAccess().console();
284 }
285 }
286 }
287 return c;
288 }
289
290 /**
291 * Returns the channel inherited from the entity that created this
292 * Java virtual machine.
293 *
294 * This method returns the channel obtained by invoking the
295 * {@link java.nio.channels.spi.SelectorProvider#inheritedChannel
296 * inheritedChannel} method of the system-wide default
297 * {@link java.nio.channels.spi.SelectorProvider} object.
298 *
299 * <p> In addition to the network-oriented channels described in
300 * {@link java.nio.channels.spi.SelectorProvider#inheritedChannel
301 * inheritedChannel}, this method may return other kinds of
302 * channels in the future.
303 *
304 * @return The inherited channel, if any, otherwise {@code null}.
305 *
306 * @throws IOException
307 * If an I/O error occurs
308 *
309 * @throws SecurityException
310 * If a security manager is present and it does not
311 * permit access to the channel.
312 *
313 * @since 1.5
314 */
315 public static Channel inheritedChannel() throws IOException {
316 return SelectorProvider.provider().inheritedChannel();
317 }
318
319 private static void checkIO() {
320 @SuppressWarnings("removal")
321 SecurityManager sm = getSecurityManager();
322 if (sm != null) {
323 sm.checkPermission(new RuntimePermission("setIO"));
324 }
325 }
326
327 private static native void setIn0(InputStream in);
328 private static native void setOut0(PrintStream out);
329 private static native void setErr0(PrintStream err);
330
331 private static class CallersHolder {
332 // Remember callers of setSecurityManager() here so that warning
333 // is only printed once for each different caller
334 final static Map<Class<?>, Boolean> callers
335 = Collections.synchronizedMap(new WeakHashMap<>());
336 }
337
338 // Remember initial System.err. setSecurityManager() warning goes here
339 private static volatile @Stable PrintStream initialErrStream;
340
341 private static URL codeSource(Class<?> clazz) {
342 PrivilegedAction<ProtectionDomain> pa = clazz::getProtectionDomain;
343 @SuppressWarnings("removal")
344 CodeSource cs = AccessController.doPrivileged(pa).getCodeSource();
345 return (cs != null) ? cs.getLocation() : null;
346 }
347
348 /**
349 * Sets the system-wide security manager.
350 *
351 * If there is a security manager already installed, this method first
352 * calls the security manager's {@code checkPermission} method
353 * with a {@code RuntimePermission("setSecurityManager")}
354 * permission to ensure it's ok to replace the existing
355 * security manager.
356 * This may result in throwing a {@code SecurityException}.
357 *
358 * <p> Otherwise, the argument is established as the current
359 * security manager. If the argument is {@code null} and no
360 * security manager has been established, then no action is taken and
361 * the method simply returns.
362 *
363 * @implNote In the JDK implementation, if the Java virtual machine is
364 * started with the system property {@code java.security.manager} not set or set to
365 * the special token "{@code disallow}" then the {@code setSecurityManager}
366 * method cannot be used to set a security manager. See the following
367 * <a href="SecurityManager.html#set-security-manager">section of the
368 * {@code SecurityManager} class specification</a> for more details.
369 *
370 * @param sm the security manager or {@code null}
371 * @throws SecurityException
372 * if the security manager has already been set and its {@code
373 * checkPermission} method doesn't allow it to be replaced
374 * @throws UnsupportedOperationException
375 * if {@code sm} is non-null and a security manager is not allowed
376 * to be set dynamically
377 * @see #getSecurityManager
378 * @see SecurityManager#checkPermission
379 * @see java.lang.RuntimePermission
380 * @deprecated This method is only useful in conjunction with
381 * {@linkplain SecurityManager the Security Manager}, which is
382 * deprecated and subject to removal in a future release.
383 * Consequently, this method is also deprecated and subject to
384 * removal. There is no replacement for the Security Manager or this
385 * method.
386 */
387 @Deprecated(since="17", forRemoval=true)
388 @CallerSensitive
389 public static void setSecurityManager(@SuppressWarnings("removal") SecurityManager sm) {
390 if (allowSecurityManager()) {
391 var callerClass = Reflection.getCallerClass();
392 if (CallersHolder.callers.putIfAbsent(callerClass, true) == null) {
393 URL url = codeSource(callerClass);
394 final String source;
395 if (url == null) {
396 source = callerClass.getName();
397 } else {
398 source = callerClass.getName() + " (" + url + ")";
399 }
400 initialErrStream.printf("""
401 WARNING: A terminally deprecated method in java.lang.System has been called
402 WARNING: System::setSecurityManager has been called by %s
403 WARNING: Please consider reporting this to the maintainers of %s
404 WARNING: System::setSecurityManager will be removed in a future release
405 """, source, callerClass.getName());
406 }
407 implSetSecurityManager(sm);
408 } else {
409 // security manager not allowed
410 if (sm != null) {
411 throw new UnsupportedOperationException(
412 "The Security Manager is deprecated and will be removed in a future release");
413 }
414 }
415 }
416
417 private static void implSetSecurityManager(@SuppressWarnings("removal") SecurityManager sm) {
418 if (security == null) {
419 // ensure image reader is initialized
420 Object.class.getResource("java/lang/ANY");
421 // ensure the default file system is initialized
422 DefaultFileSystemProvider.theFileSystem();
423 }
424 if (sm != null) {
425 try {
426 // pre-populates the SecurityManager.packageAccess cache
427 // to avoid recursive permission checking issues with custom
428 // SecurityManager implementations
429 sm.checkPackageAccess("java.lang");
430 } catch (Exception e) {
431 // no-op
432 }
433 }
434 setSecurityManager0(sm);
435 }
436
437 @SuppressWarnings("removal")
438 private static synchronized
439 void setSecurityManager0(final SecurityManager s) {
440 SecurityManager sm = getSecurityManager();
441 if (sm != null) {
442 // ask the currently installed security manager if we
443 // can replace it.
444 sm.checkPermission(new RuntimePermission("setSecurityManager"));
445 }
446
447 if ((s != null) && (s.getClass().getClassLoader() != null)) {
448 // New security manager class is not on bootstrap classpath.
449 // Force policy to get initialized before we install the new
450 // security manager, in order to prevent infinite loops when
451 // trying to initialize the policy (which usually involves
452 // accessing some security and/or system properties, which in turn
453 // calls the installed security manager's checkPermission method
454 // which will loop infinitely if there is a non-system class
455 // (in this case: the new security manager class) on the stack).
456 AccessController.doPrivileged(new PrivilegedAction<>() {
457 public Object run() {
458 s.getClass().getProtectionDomain().implies
459 (SecurityConstants.ALL_PERMISSION);
460 return null;
461 }
462 });
463 }
464
465 security = s;
466 }
467
468 /**
469 * Gets the system-wide security manager.
470 *
471 * @return if a security manager has already been established for the
472 * current application, then that security manager is returned;
473 * otherwise, {@code null} is returned.
474 * @see #setSecurityManager
475 * @deprecated This method is only useful in conjunction with
476 * {@linkplain SecurityManager the Security Manager}, which is
477 * deprecated and subject to removal in a future release.
478 * Consequently, this method is also deprecated and subject to
479 * removal. There is no replacement for the Security Manager or this
480 * method.
481 */
482 @SuppressWarnings("removal")
483 @Deprecated(since="17", forRemoval=true)
484 public static SecurityManager getSecurityManager() {
485 if (allowSecurityManager()) {
486 return security;
487 } else {
488 return null;
489 }
490 }
491
492 /**
493 * Returns the current time in milliseconds. Note that
494 * while the unit of time of the return value is a millisecond,
495 * the granularity of the value depends on the underlying
496 * operating system and may be larger. For example, many
497 * operating systems measure time in units of tens of
498 * milliseconds.
499 *
500 * <p> See the description of the class {@code Date} for
501 * a discussion of slight discrepancies that may arise between
502 * "computer time" and coordinated universal time (UTC).
503 *
504 * @return the difference, measured in milliseconds, between
505 * the current time and midnight, January 1, 1970 UTC.
506 * @see java.util.Date
507 */
508 @IntrinsicCandidate
509 public static native long currentTimeMillis();
510
511 /**
512 * Returns the current value of the running Java Virtual Machine's
513 * high-resolution time source, in nanoseconds.
514 *
515 * This method can only be used to measure elapsed time and is
516 * not related to any other notion of system or wall-clock time.
517 * The value returned represents nanoseconds since some fixed but
518 * arbitrary <i>origin</i> time (perhaps in the future, so values
519 * may be negative). The same origin is used by all invocations of
520 * this method in an instance of a Java virtual machine; other
521 * virtual machine instances are likely to use a different origin.
522 *
523 * <p>This method provides nanosecond precision, but not necessarily
524 * nanosecond resolution (that is, how frequently the value changes)
525 * - no guarantees are made except that the resolution is at least as
526 * good as that of {@link #currentTimeMillis()}.
527 *
528 * <p>Differences in successive calls that span greater than
529 * approximately 292 years (2<sup>63</sup> nanoseconds) will not
530 * correctly compute elapsed time due to numerical overflow.
531 *
532 * <p>The values returned by this method become meaningful only when
533 * the difference between two such values, obtained within the same
534 * instance of a Java virtual machine, is computed.
535 *
536 * <p>For example, to measure how long some code takes to execute:
537 * <pre> {@code
538 * long startTime = System.nanoTime();
539 * // ... the code being measured ...
540 * long elapsedNanos = System.nanoTime() - startTime;}</pre>
541 *
542 * <p>To compare elapsed time against a timeout, use <pre> {@code
543 * if (System.nanoTime() - startTime >= timeoutNanos) ...}</pre>
544 * instead of <pre> {@code
545 * if (System.nanoTime() >= startTime + timeoutNanos) ...}</pre>
546 * because of the possibility of numerical overflow.
547 *
548 * @return the current value of the running Java Virtual Machine's
549 * high-resolution time source, in nanoseconds
550 * @since 1.5
551 */
552 @IntrinsicCandidate
553 public static native long nanoTime();
554
555 /**
556 * Copies an array from the specified source array, beginning at the
557 * specified position, to the specified position of the destination array.
558 * A subsequence of array components are copied from the source
559 * array referenced by {@code src} to the destination array
560 * referenced by {@code dest}. The number of components copied is
561 * equal to the {@code length} argument. The components at
562 * positions {@code srcPos} through
563 * {@code srcPos+length-1} in the source array are copied into
564 * positions {@code destPos} through
565 * {@code destPos+length-1}, respectively, of the destination
566 * array.
567 * <p>
568 * If the {@code src} and {@code dest} arguments refer to the
569 * same array object, then the copying is performed as if the
570 * components at positions {@code srcPos} through
571 * {@code srcPos+length-1} were first copied to a temporary
572 * array with {@code length} components and then the contents of
573 * the temporary array were copied into positions
574 * {@code destPos} through {@code destPos+length-1} of the
575 * destination array.
576 * <p>
577 * If {@code dest} is {@code null}, then a
578 * {@code NullPointerException} is thrown.
579 * <p>
580 * If {@code src} is {@code null}, then a
581 * {@code NullPointerException} is thrown and the destination
582 * array is not modified.
583 * <p>
584 * Otherwise, if any of the following is true, an
585 * {@code ArrayStoreException} is thrown and the destination is
586 * not modified:
587 * <ul>
588 * <li>The {@code src} argument refers to an object that is not an
589 * array.
590 * <li>The {@code dest} argument refers to an object that is not an
591 * array.
592 * <li>The {@code src} argument and {@code dest} argument refer
593 * to arrays whose component types are different primitive types.
594 * <li>The {@code src} argument refers to an array with a primitive
595 * component type and the {@code dest} argument refers to an array
596 * with a reference component type.
597 * <li>The {@code src} argument refers to an array with a reference
598 * component type and the {@code dest} argument refers to an array
599 * with a primitive component type.
600 * </ul>
601 * <p>
602 * Otherwise, if any of the following is true, an
603 * {@code IndexOutOfBoundsException} is
604 * thrown and the destination is not modified:
605 * <ul>
606 * <li>The {@code srcPos} argument is negative.
607 * <li>The {@code destPos} argument is negative.
608 * <li>The {@code length} argument is negative.
609 * <li>{@code srcPos+length} is greater than
610 * {@code src.length}, the length of the source array.
611 * <li>{@code destPos+length} is greater than
612 * {@code dest.length}, the length of the destination array.
613 * </ul>
614 * <p>
615 * Otherwise, if any actual component of the source array from
616 * position {@code srcPos} through
617 * {@code srcPos+length-1} cannot be converted to the component
618 * type of the destination array by assignment conversion, an
619 * {@code ArrayStoreException} is thrown. In this case, let
620 * <b><i>k</i></b> be the smallest nonnegative integer less than
621 * length such that {@code src[srcPos+}<i>k</i>{@code ]}
622 * cannot be converted to the component type of the destination
623 * array; when the exception is thrown, source array components from
624 * positions {@code srcPos} through
625 * {@code srcPos+}<i>k</i>{@code -1}
626 * will already have been copied to destination array positions
627 * {@code destPos} through
628 * {@code destPos+}<i>k</I>{@code -1} and no other
629 * positions of the destination array will have been modified.
630 * (Because of the restrictions already itemized, this
631 * paragraph effectively applies only to the situation where both
632 * arrays have component types that are reference types.)
633 *
634 * @param src the source array.
635 * @param srcPos starting position in the source array.
636 * @param dest the destination array.
637 * @param destPos starting position in the destination data.
638 * @param length the number of array elements to be copied.
639 * @throws IndexOutOfBoundsException if copying would cause
640 * access of data outside array bounds.
641 * @throws ArrayStoreException if an element in the {@code src}
642 * array could not be stored into the {@code dest} array
643 * because of a type mismatch.
644 * @throws NullPointerException if either {@code src} or
645 * {@code dest} is {@code null}.
646 */
647 @IntrinsicCandidate
648 public static native void arraycopy(Object src, int srcPos,
649 Object dest, int destPos,
650 int length);
651
652 /**
653 * Returns the same hash code for the given object as
654 * would be returned by the default method hashCode(),
655 * whether or not the given object's class overrides
656 * hashCode().
657 * The hash code for the null reference is zero.
658 *
659 * @param x object for which the hashCode is to be calculated
660 * @return the hashCode
661 * @since 1.1
662 * @see Object#hashCode
663 * @see java.util.Objects#hashCode(Object)
664 */
665 @IntrinsicCandidate
666 public static native int identityHashCode(Object x);
667
668 /**
669 * System properties.
670 *
671 * See {@linkplain #getProperties getProperties} for details.
672 */
673 private static Properties props;
674
675 /**
676 * Determines the current system properties.
677 *
678 * First, if there is a security manager, its
679 * {@code checkPropertiesAccess} method is called with no
680 * arguments. This may result in a security exception.
681 * <p>
682 * The current set of system properties for use by the
683 * {@link #getProperty(String)} method is returned as a
684 * {@code Properties} object. If there is no current set of
685 * system properties, a set of system properties is first created and
686 * initialized. This set of system properties includes a value
687 * for each of the following keys unless the description of the associated
688 * value indicates that the value is optional.
689 * <table class="striped" style="text-align:left">
690 * <caption style="display:none">Shows property keys and associated values</caption>
691 * <thead>
692 * <tr><th scope="col">Key</th>
693 * <th scope="col">Description of Associated Value</th></tr>
694 * </thead>
695 * <tbody>
696 * <tr><th scope="row">{@systemProperty java.version}</th>
697 * <td>Java Runtime Environment version, which may be interpreted
698 * as a {@link Runtime.Version}</td></tr>
699 * <tr><th scope="row">{@systemProperty java.version.date}</th>
700 * <td>Java Runtime Environment version date, in ISO-8601 YYYY-MM-DD
701 * format, which may be interpreted as a {@link
702 * java.time.LocalDate}</td></tr>
703 * <tr><th scope="row">{@systemProperty java.vendor}</th>
704 * <td>Java Runtime Environment vendor</td></tr>
705 * <tr><th scope="row">{@systemProperty java.vendor.url}</th>
706 * <td>Java vendor URL</td></tr>
707 * <tr><th scope="row">{@systemProperty java.vendor.version}</th>
708 * <td>Java vendor version <em>(optional)</em> </td></tr>
709 * <tr><th scope="row">{@systemProperty java.home}</th>
710 * <td>Java installation directory</td></tr>
711 * <tr><th scope="row">{@systemProperty java.vm.specification.version}</th>
712 * <td>Java Virtual Machine specification version, whose value is the
713 * {@linkplain Runtime.Version#feature feature} element of the
714 * {@linkplain Runtime#version() runtime version}</td></tr>
715 * <tr><th scope="row">{@systemProperty java.vm.specification.vendor}</th>
716 * <td>Java Virtual Machine specification vendor</td></tr>
717 * <tr><th scope="row">{@systemProperty java.vm.specification.name}</th>
718 * <td>Java Virtual Machine specification name</td></tr>
719 * <tr><th scope="row">{@systemProperty java.vm.version}</th>
720 * <td>Java Virtual Machine implementation version which may be
721 * interpreted as a {@link Runtime.Version}</td></tr>
722 * <tr><th scope="row">{@systemProperty java.vm.vendor}</th>
723 * <td>Java Virtual Machine implementation vendor</td></tr>
724 * <tr><th scope="row">{@systemProperty java.vm.name}</th>
725 * <td>Java Virtual Machine implementation name</td></tr>
726 * <tr><th scope="row">{@systemProperty java.specification.version}</th>
727 * <td>Java Runtime Environment specification version, whose value is
728 * the {@linkplain Runtime.Version#feature feature} element of the
729 * {@linkplain Runtime#version() runtime version}</td></tr>
730 * <tr><th scope="row">{@systemProperty java.specification.vendor}</th>
731 * <td>Java Runtime Environment specification vendor</td></tr>
732 * <tr><th scope="row">{@systemProperty java.specification.name}</th>
733 * <td>Java Runtime Environment specification name</td></tr>
734 * <tr><th scope="row">{@systemProperty java.class.version}</th>
735 * <td>Java class format version number</td></tr>
736 * <tr><th scope="row">{@systemProperty java.class.path}</th>
737 * <td>Java class path (refer to
738 * {@link ClassLoader#getSystemClassLoader()} for details)</td></tr>
739 * <tr><th scope="row">{@systemProperty java.library.path}</th>
740 * <td>List of paths to search when loading libraries</td></tr>
741 * <tr><th scope="row">{@systemProperty java.io.tmpdir}</th>
742 * <td>Default temp file path</td></tr>
743 * <tr><th scope="row">{@systemProperty java.compiler}</th>
744 * <td>Name of JIT compiler to use</td></tr>
745 * <tr><th scope="row">{@systemProperty os.name}</th>
746 * <td>Operating system name</td></tr>
747 * <tr><th scope="row">{@systemProperty os.arch}</th>
748 * <td>Operating system architecture</td></tr>
749 * <tr><th scope="row">{@systemProperty os.version}</th>
750 * <td>Operating system version</td></tr>
751 * <tr><th scope="row">{@systemProperty file.separator}</th>
752 * <td>File separator ("/" on UNIX)</td></tr>
753 * <tr><th scope="row">{@systemProperty path.separator}</th>
754 * <td>Path separator (":" on UNIX)</td></tr>
755 * <tr><th scope="row">{@systemProperty line.separator}</th>
756 * <td>Line separator ("\n" on UNIX)</td></tr>
757 * <tr><th scope="row">{@systemProperty user.name}</th>
758 * <td>User's account name</td></tr>
759 * <tr><th scope="row">{@systemProperty user.home}</th>
760 * <td>User's home directory</td></tr>
761 * <tr><th scope="row">{@systemProperty user.dir}</th>
762 * <td>User's current working directory</td></tr>
763 * <tr><th scope="row">{@systemProperty native.encoding}</th>
764 * <td>Character encoding name derived from the host environment and/or
765 * the user's settings. Setting this system property has no effect.</td></tr>
766 * </tbody>
767 * </table>
768 * <p>
769 * Multiple paths in a system property value are separated by the path
770 * separator character of the platform.
771 * <p>
772 * Note that even if the security manager does not permit the
773 * {@code getProperties} operation, it may choose to permit the
774 * {@link #getProperty(String)} operation.
775 *
776 * @apiNote
777 * <strong>Changing a standard system property may have unpredictable results
778 * unless otherwise specified.</strong>
779 * Property values may be cached during initialization or on first use.
780 * Setting a standard property after initialization using {@link #getProperties()},
781 * {@link #setProperties(Properties)}, {@link #setProperty(String, String)}, or
782 * {@link #clearProperty(String)} may not have the desired effect.
783 *
784 * @implNote
785 * In addition to the standard system properties, the system
786 * properties may include the following keys:
787 * <table class="striped">
788 * <caption style="display:none">Shows property keys and associated values</caption>
789 * <thead>
790 * <tr><th scope="col">Key</th>
791 * <th scope="col">Description of Associated Value</th></tr>
792 * </thead>
793 * <tbody>
794 * <tr><th scope="row">{@systemProperty jdk.module.path}</th>
795 * <td>The application module path</td></tr>
796 * <tr><th scope="row">{@systemProperty jdk.module.upgrade.path}</th>
797 * <td>The upgrade module path</td></tr>
798 * <tr><th scope="row">{@systemProperty jdk.module.main}</th>
799 * <td>The module name of the initial/main module</td></tr>
800 * <tr><th scope="row">{@systemProperty jdk.module.main.class}</th>
801 * <td>The main class name of the initial module</td></tr>
802 * <tr><th scope="row">{@systemProperty file.encoding}</th>
803 * <td>The name of the default charset, defaults to {@code UTF-8}.
804 * The property may be set on the command line to the value
805 * {@code UTF-8} or {@code COMPAT}. If set on the command line to
806 * the value {@code COMPAT} then the value is replaced with the
807 * value of the {@code native.encoding} property during startup.
808 * Setting the property to a value other than {@code UTF-8} or
809 * {@code COMPAT} leads to unspecified behavior.
810 * </td></tr>
811 * </tbody>
812 * </table>
813 *
814 * @return the system properties
815 * @throws SecurityException if a security manager exists and its
816 * {@code checkPropertiesAccess} method doesn't allow access
817 * to the system properties.
818 * @see #setProperties
819 * @see java.lang.SecurityException
820 * @see java.lang.SecurityManager#checkPropertiesAccess()
821 * @see java.util.Properties
822 */
823 public static Properties getProperties() {
824 @SuppressWarnings("removal")
825 SecurityManager sm = getSecurityManager();
826 if (sm != null) {
827 sm.checkPropertiesAccess();
828 }
829
830 return props;
831 }
832
833 /**
834 * Returns the system-dependent line separator string. It always
835 * returns the same value - the initial value of the {@linkplain
836 * #getProperty(String) system property} {@code line.separator}.
837 *
838 * <p>On UNIX systems, it returns {@code "\n"}; on Microsoft
839 * Windows systems it returns {@code "\r\n"}.
840 *
841 * @return the system-dependent line separator string
842 * @since 1.7
843 */
844 public static String lineSeparator() {
845 return lineSeparator;
846 }
847
848 private static String lineSeparator;
849
850 /**
851 * Sets the system properties to the {@code Properties} argument.
852 *
853 * First, if there is a security manager, its
854 * {@code checkPropertiesAccess} method is called with no
855 * arguments. This may result in a security exception.
856 * <p>
857 * The argument becomes the current set of system properties for use
858 * by the {@link #getProperty(String)} method. If the argument is
859 * {@code null}, then the current set of system properties is
860 * forgotten.
861 *
862 * @apiNote
863 * <strong>Changing a standard system property may have unpredictable results
864 * unless otherwise specified</strong>.
865 * See {@linkplain #getProperties getProperties} for details.
866 *
867 * @param props the new system properties.
868 * @throws SecurityException if a security manager exists and its
869 * {@code checkPropertiesAccess} method doesn't allow access
870 * to the system properties.
871 * @see #getProperties
872 * @see java.util.Properties
873 * @see java.lang.SecurityException
874 * @see java.lang.SecurityManager#checkPropertiesAccess()
875 */
876 public static void setProperties(Properties props) {
877 @SuppressWarnings("removal")
878 SecurityManager sm = getSecurityManager();
879 if (sm != null) {
880 sm.checkPropertiesAccess();
881 }
882
883 if (props == null) {
884 Map<String, String> tempProps = SystemProps.initProperties();
885 VersionProps.init(tempProps);
886 props = createProperties(tempProps);
887 }
888 System.props = props;
889 }
890
891 /**
892 * Gets the system property indicated by the specified key.
893 *
894 * First, if there is a security manager, its
895 * {@code checkPropertyAccess} method is called with the key as
896 * its argument. This may result in a SecurityException.
897 * <p>
898 * If there is no current set of system properties, a set of system
899 * properties is first created and initialized in the same manner as
900 * for the {@code getProperties} method.
901 *
902 * @apiNote
903 * <strong>Changing a standard system property may have unpredictable results
904 * unless otherwise specified</strong>.
905 * See {@linkplain #getProperties getProperties} for details.
906 *
907 * @param key the name of the system property.
908 * @return the string value of the system property,
909 * or {@code null} if there is no property with that key.
910 *
911 * @throws SecurityException if a security manager exists and its
912 * {@code checkPropertyAccess} method doesn't allow
913 * access to the specified system property.
914 * @throws NullPointerException if {@code key} is {@code null}.
915 * @throws IllegalArgumentException if {@code key} is empty.
916 * @see #setProperty
917 * @see java.lang.SecurityException
918 * @see java.lang.SecurityManager#checkPropertyAccess(java.lang.String)
919 * @see java.lang.System#getProperties()
920 */
921 public static String getProperty(String key) {
922 checkKey(key);
923 @SuppressWarnings("removal")
924 SecurityManager sm = getSecurityManager();
925 if (sm != null) {
926 sm.checkPropertyAccess(key);
927 }
928
929 return props.getProperty(key);
930 }
931
932 /**
933 * Gets the system property indicated by the specified key.
934 *
935 * First, if there is a security manager, its
936 * {@code checkPropertyAccess} method is called with the
937 * {@code key} as its argument.
938 * <p>
939 * If there is no current set of system properties, a set of system
940 * properties is first created and initialized in the same manner as
941 * for the {@code getProperties} method.
942 *
943 * @param key the name of the system property.
944 * @param def a default value.
945 * @return the string value of the system property,
946 * or the default value if there is no property with that key.
947 *
948 * @throws SecurityException if a security manager exists and its
949 * {@code checkPropertyAccess} method doesn't allow
950 * access to the specified system property.
951 * @throws NullPointerException if {@code key} is {@code null}.
952 * @throws IllegalArgumentException if {@code key} is empty.
953 * @see #setProperty
954 * @see java.lang.SecurityManager#checkPropertyAccess(java.lang.String)
955 * @see java.lang.System#getProperties()
956 */
957 public static String getProperty(String key, String def) {
958 checkKey(key);
959 @SuppressWarnings("removal")
960 SecurityManager sm = getSecurityManager();
961 if (sm != null) {
962 sm.checkPropertyAccess(key);
963 }
964
965 return props.getProperty(key, def);
966 }
967
968 /**
969 * Sets the system property indicated by the specified key.
970 *
971 * First, if a security manager exists, its
972 * {@code SecurityManager.checkPermission} method
973 * is called with a {@code PropertyPermission(key, "write")}
974 * permission. This may result in a SecurityException being thrown.
975 * If no exception is thrown, the specified property is set to the given
976 * value.
977 *
978 * @apiNote
979 * <strong>Changing a standard system property may have unpredictable results
980 * unless otherwise specified</strong>.
981 * See {@linkplain #getProperties getProperties} for details.
982 *
983 * @param key the name of the system property.
984 * @param value the value of the system property.
985 * @return the previous value of the system property,
986 * or {@code null} if it did not have one.
987 *
988 * @throws SecurityException if a security manager exists and its
989 * {@code checkPermission} method doesn't allow
990 * setting of the specified property.
991 * @throws NullPointerException if {@code key} or
992 * {@code value} is {@code null}.
993 * @throws IllegalArgumentException if {@code key} is empty.
994 * @see #getProperty
995 * @see java.lang.System#getProperty(java.lang.String)
996 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
997 * @see java.util.PropertyPermission
998 * @see SecurityManager#checkPermission
999 * @since 1.2
1000 */
1001 public static String setProperty(String key, String value) {
1002 checkKey(key);
1003 @SuppressWarnings("removal")
1004 SecurityManager sm = getSecurityManager();
1005 if (sm != null) {
1006 sm.checkPermission(new PropertyPermission(key,
1007 SecurityConstants.PROPERTY_WRITE_ACTION));
1008 }
1009
1010 return (String) props.setProperty(key, value);
1011 }
1012
1013 /**
1014 * Removes the system property indicated by the specified key.
1015 *
1016 * First, if a security manager exists, its
1017 * {@code SecurityManager.checkPermission} method
1018 * is called with a {@code PropertyPermission(key, "write")}
1019 * permission. This may result in a SecurityException being thrown.
1020 * If no exception is thrown, the specified property is removed.
1021 *
1022 * @apiNote
1023 * <strong>Changing a standard system property may have unpredictable results
1024 * unless otherwise specified</strong>.
1025 * See {@linkplain #getProperties getProperties} method for details.
1026 *
1027 * @param key the name of the system property to be removed.
1028 * @return the previous string value of the system property,
1029 * or {@code null} if there was no property with that key.
1030 *
1031 * @throws SecurityException if a security manager exists and its
1032 * {@code checkPropertyAccess} method doesn't allow
1033 * access to the specified system property.
1034 * @throws NullPointerException if {@code key} is {@code null}.
1035 * @throws IllegalArgumentException if {@code key} is empty.
1036 * @see #getProperty
1037 * @see #setProperty
1038 * @see java.util.Properties
1039 * @see java.lang.SecurityException
1040 * @see java.lang.SecurityManager#checkPropertiesAccess()
1041 * @since 1.5
1042 */
1043 public static String clearProperty(String key) {
1044 checkKey(key);
1045 @SuppressWarnings("removal")
1046 SecurityManager sm = getSecurityManager();
1047 if (sm != null) {
1048 sm.checkPermission(new PropertyPermission(key, "write"));
1049 }
1050
1051 return (String) props.remove(key);
1052 }
1053
1054 private static void checkKey(String key) {
1055 if (key == null) {
1056 throw new NullPointerException("key can't be null");
1057 }
1058 if (key.isEmpty()) {
1059 throw new IllegalArgumentException("key can't be empty");
1060 }
1061 }
1062
1063 /**
1064 * Gets the value of the specified environment variable. An
1065 * environment variable is a system-dependent external named
1066 * value.
1067 *
1068 * <p>If a security manager exists, its
1069 * {@link SecurityManager#checkPermission checkPermission}
1070 * method is called with a
1071 * {@link RuntimePermission RuntimePermission("getenv."+name)}
1072 * permission. This may result in a {@link SecurityException}
1073 * being thrown. If no exception is thrown the value of the
1074 * variable {@code name} is returned.
1075 *
1076 * <p><a id="EnvironmentVSSystemProperties"><i>System
1077 * properties</i> and <i>environment variables</i></a> are both
1078 * conceptually mappings between names and values. Both
1079 * mechanisms can be used to pass user-defined information to a
1080 * Java process. Environment variables have a more global effect,
1081 * because they are visible to all descendants of the process
1082 * which defines them, not just the immediate Java subprocess.
1083 * They can have subtly different semantics, such as case
1084 * insensitivity, on different operating systems. For these
1085 * reasons, environment variables are more likely to have
1086 * unintended side effects. It is best to use system properties
1087 * where possible. Environment variables should be used when a
1088 * global effect is desired, or when an external system interface
1089 * requires an environment variable (such as {@code PATH}).
1090 *
1091 * <p>On UNIX systems the alphabetic case of {@code name} is
1092 * typically significant, while on Microsoft Windows systems it is
1093 * typically not. For example, the expression
1094 * {@code System.getenv("FOO").equals(System.getenv("foo"))}
1095 * is likely to be true on Microsoft Windows.
1096 *
1097 * @param name the name of the environment variable
1098 * @return the string value of the variable, or {@code null}
1099 * if the variable is not defined in the system environment
1100 * @throws NullPointerException if {@code name} is {@code null}
1101 * @throws SecurityException
1102 * if a security manager exists and its
1103 * {@link SecurityManager#checkPermission checkPermission}
1104 * method doesn't allow access to the environment variable
1105 * {@code name}
1106 * @see #getenv()
1107 * @see ProcessBuilder#environment()
1108 */
1109 public static String getenv(String name) {
1110 @SuppressWarnings("removal")
1111 SecurityManager sm = getSecurityManager();
1112 if (sm != null) {
1113 sm.checkPermission(new RuntimePermission("getenv."+name));
1114 }
1115
1116 return ProcessEnvironment.getenv(name);
1117 }
1118
1119
1120 /**
1121 * Returns an unmodifiable string map view of the current system environment.
1122 * The environment is a system-dependent mapping from names to
1123 * values which is passed from parent to child processes.
1124 *
1125 * <p>If the system does not support environment variables, an
1126 * empty map is returned.
1127 *
1128 * <p>The returned map will never contain null keys or values.
1129 * Attempting to query the presence of a null key or value will
1130 * throw a {@link NullPointerException}. Attempting to query
1131 * the presence of a key or value which is not of type
1132 * {@link String} will throw a {@link ClassCastException}.
1133 *
1134 * <p>The returned map and its collection views may not obey the
1135 * general contract of the {@link Object#equals} and
1136 * {@link Object#hashCode} methods.
1137 *
1138 * <p>The returned map is typically case-sensitive on all platforms.
1139 *
1140 * <p>If a security manager exists, its
1141 * {@link SecurityManager#checkPermission checkPermission}
1142 * method is called with a
1143 * {@link RuntimePermission RuntimePermission("getenv.*")} permission.
1144 * This may result in a {@link SecurityException} being thrown.
1145 *
1146 * <p>When passing information to a Java subprocess,
1147 * <a href=#EnvironmentVSSystemProperties>system properties</a>
1148 * are generally preferred over environment variables.
1149 *
1150 * @return the environment as a map of variable names to values
1151 * @throws SecurityException
1152 * if a security manager exists and its
1153 * {@link SecurityManager#checkPermission checkPermission}
1154 * method doesn't allow access to the process environment
1155 * @see #getenv(String)
1156 * @see ProcessBuilder#environment()
1157 * @since 1.5
1158 */
1159 public static java.util.Map<String,String> getenv() {
1160 @SuppressWarnings("removal")
1161 SecurityManager sm = getSecurityManager();
1162 if (sm != null) {
1163 sm.checkPermission(new RuntimePermission("getenv.*"));
1164 }
1165
1166 return ProcessEnvironment.getenv();
1167 }
1168
1169 /**
1170 * {@code System.Logger} instances log messages that will be
1171 * routed to the underlying logging framework the {@link System.LoggerFinder
1172 * LoggerFinder} uses.
1173 *
1174 * {@code System.Logger} instances are typically obtained from
1175 * the {@link java.lang.System System} class, by calling
1176 * {@link java.lang.System#getLogger(java.lang.String) System.getLogger(loggerName)}
1177 * or {@link java.lang.System#getLogger(java.lang.String, java.util.ResourceBundle)
1178 * System.getLogger(loggerName, bundle)}.
1179 *
1180 * @see java.lang.System#getLogger(java.lang.String)
1181 * @see java.lang.System#getLogger(java.lang.String, java.util.ResourceBundle)
1182 * @see java.lang.System.LoggerFinder
1183 *
1184 * @since 9
1185 */
1186 public interface Logger {
1187
1188 /**
1189 * System {@linkplain Logger loggers} levels.
1190 *
1191 * A level has a {@linkplain #getName() name} and {@linkplain
1192 * #getSeverity() severity}.
1193 * Level values are {@link #ALL}, {@link #TRACE}, {@link #DEBUG},
1194 * {@link #INFO}, {@link #WARNING}, {@link #ERROR}, {@link #OFF},
1195 * by order of increasing severity.
1196 * <br>
1197 * {@link #ALL} and {@link #OFF}
1198 * are simple markers with severities mapped respectively to
1199 * {@link java.lang.Integer#MIN_VALUE Integer.MIN_VALUE} and
1200 * {@link java.lang.Integer#MAX_VALUE Integer.MAX_VALUE}.
1201 * <p>
1202 * <b>Severity values and Mapping to {@code java.util.logging.Level}.</b>
1203 * <p>
1204 * {@linkplain System.Logger.Level System logger levels} are mapped to
1205 * {@linkplain java.util.logging.Level java.util.logging levels}
1206 * of corresponding severity.
1207 * <br>The mapping is as follows:
1208 * <br><br>
1209 * <table class="striped">
1210 * <caption>System.Logger Severity Level Mapping</caption>
1211 * <thead>
1212 * <tr><th scope="col">System.Logger Levels</th>
1213 * <th scope="col">java.util.logging Levels</th>
1214 * </thead>
1215 * <tbody>
1216 * <tr><th scope="row">{@link Logger.Level#ALL ALL}</th>
1217 * <td>{@link java.util.logging.Level#ALL ALL}</td>
1218 * <tr><th scope="row">{@link Logger.Level#TRACE TRACE}</th>
1219 * <td>{@link java.util.logging.Level#FINER FINER}</td>
1220 * <tr><th scope="row">{@link Logger.Level#DEBUG DEBUG}</th>
1221 * <td>{@link java.util.logging.Level#FINE FINE}</td>
1222 * <tr><th scope="row">{@link Logger.Level#INFO INFO}</th>
1223 * <td>{@link java.util.logging.Level#INFO INFO}</td>
1224 * <tr><th scope="row">{@link Logger.Level#WARNING WARNING}</th>
1225 * <td>{@link java.util.logging.Level#WARNING WARNING}</td>
1226 * <tr><th scope="row">{@link Logger.Level#ERROR ERROR}</th>
1227 * <td>{@link java.util.logging.Level#SEVERE SEVERE}</td>
1228 * <tr><th scope="row">{@link Logger.Level#OFF OFF}</th>
1229 * <td>{@link java.util.logging.Level#OFF OFF}</td>
1230 * </tbody>
1231 * </table>
1232 *
1233 * @since 9
1234 *
1235 * @see java.lang.System.LoggerFinder
1236 * @see java.lang.System.Logger
1237 */
1238 public enum Level {
1239
1240 // for convenience, we're reusing java.util.logging.Level int values
1241 // the mapping logic in sun.util.logging.PlatformLogger depends
1242 // on this.
1243 /**
1244 * A marker to indicate that all levels are enabled.
1245 * This level {@linkplain #getSeverity() severity} is
1246 * {@link Integer#MIN_VALUE}.
1247 */
1248 ALL(Integer.MIN_VALUE), // typically mapped to/from j.u.l.Level.ALL
1249 /**
1250 * {@code TRACE} level: usually used to log diagnostic information.
1251 * This level {@linkplain #getSeverity() severity} is
1252 * {@code 400}.
1253 */
1254 TRACE(400), // typically mapped to/from j.u.l.Level.FINER
1255 /**
1256 * {@code DEBUG} level: usually used to log debug information traces.
1257 * This level {@linkplain #getSeverity() severity} is
1258 * {@code 500}.
1259 */
1260 DEBUG(500), // typically mapped to/from j.u.l.Level.FINEST/FINE/CONFIG
1261 /**
1262 * {@code INFO} level: usually used to log information messages.
1263 * This level {@linkplain #getSeverity() severity} is
1264 * {@code 800}.
1265 */
1266 INFO(800), // typically mapped to/from j.u.l.Level.INFO
1267 /**
1268 * {@code WARNING} level: usually used to log warning messages.
1269 * This level {@linkplain #getSeverity() severity} is
1270 * {@code 900}.
1271 */
1272 WARNING(900), // typically mapped to/from j.u.l.Level.WARNING
1273 /**
1274 * {@code ERROR} level: usually used to log error messages.
1275 * This level {@linkplain #getSeverity() severity} is
1276 * {@code 1000}.
1277 */
1278 ERROR(1000), // typically mapped to/from j.u.l.Level.SEVERE
1279 /**
1280 * A marker to indicate that all levels are disabled.
1281 * This level {@linkplain #getSeverity() severity} is
1282 * {@link Integer#MAX_VALUE}.
1283 */
1284 OFF(Integer.MAX_VALUE); // typically mapped to/from j.u.l.Level.OFF
1285
1286 private final int severity;
1287
1288 private Level(int severity) {
1289 this.severity = severity;
1290 }
1291
1292 /**
1293 * Returns the name of this level.
1294 * @return this level {@linkplain #name()}.
1295 */
1296 public final String getName() {
1297 return name();
1298 }
1299
1300 /**
1301 * Returns the severity of this level.
1302 * A higher severity means a more severe condition.
1303 * @return this level severity.
1304 */
1305 public final int getSeverity() {
1306 return severity;
1307 }
1308 }
1309
1310 /**
1311 * Returns the name of this logger.
1312 *
1313 * @return the logger name.
1314 */
1315 public String getName();
1316
1317 /**
1318 * Checks if a message of the given level would be logged by
1319 * this logger.
1320 *
1321 * @param level the log message level.
1322 * @return {@code true} if the given log message level is currently
1323 * being logged.
1324 *
1325 * @throws NullPointerException if {@code level} is {@code null}.
1326 */
1327 public boolean isLoggable(Level level);
1328
1329 /**
1330 * Logs a message.
1331 *
1332 * @implSpec The default implementation for this method calls
1333 * {@code this.log(level, (ResourceBundle)null, msg, (Object[])null);}
1334 *
1335 * @param level the log message level.
1336 * @param msg the string message (or a key in the message catalog, if
1337 * this logger is a {@link
1338 * LoggerFinder#getLocalizedLogger(java.lang.String,
1339 * java.util.ResourceBundle, java.lang.Module) localized logger});
1340 * can be {@code null}.
1341 *
1342 * @throws NullPointerException if {@code level} is {@code null}.
1343 */
1344 public default void log(Level level, String msg) {
1345 log(level, (ResourceBundle) null, msg, (Object[]) null);
1346 }
1347
1348 /**
1349 * Logs a lazily supplied message.
1350 *
1351 * If the logger is currently enabled for the given log message level
1352 * then a message is logged that is the result produced by the
1353 * given supplier function. Otherwise, the supplier is not operated on.
1354 *
1355 * @implSpec When logging is enabled for the given level, the default
1356 * implementation for this method calls
1357 * {@code this.log(level, (ResourceBundle)null, msgSupplier.get(), (Object[])null);}
1358 *
1359 * @param level the log message level.
1360 * @param msgSupplier a supplier function that produces a message.
1361 *
1362 * @throws NullPointerException if {@code level} is {@code null},
1363 * or {@code msgSupplier} is {@code null}.
1364 */
1365 public default void log(Level level, Supplier<String> msgSupplier) {
1366 Objects.requireNonNull(msgSupplier);
1367 if (isLoggable(Objects.requireNonNull(level))) {
1368 log(level, (ResourceBundle) null, msgSupplier.get(), (Object[]) null);
1369 }
1370 }
1371
1372 /**
1373 * Logs a message produced from the given object.
1374 *
1375 * If the logger is currently enabled for the given log message level then
1376 * a message is logged that, by default, is the result produced from
1377 * calling toString on the given object.
1378 * Otherwise, the object is not operated on.
1379 *
1380 * @implSpec When logging is enabled for the given level, the default
1381 * implementation for this method calls
1382 * {@code this.log(level, (ResourceBundle)null, obj.toString(), (Object[])null);}
1383 *
1384 * @param level the log message level.
1385 * @param obj the object to log.
1386 *
1387 * @throws NullPointerException if {@code level} is {@code null}, or
1388 * {@code obj} is {@code null}.
1389 */
1390 public default void log(Level level, Object obj) {
1391 Objects.requireNonNull(obj);
1392 if (isLoggable(Objects.requireNonNull(level))) {
1393 this.log(level, (ResourceBundle) null, obj.toString(), (Object[]) null);
1394 }
1395 }
1396
1397 /**
1398 * Logs a message associated with a given throwable.
1399 *
1400 * @implSpec The default implementation for this method calls
1401 * {@code this.log(level, (ResourceBundle)null, msg, thrown);}
1402 *
1403 * @param level the log message level.
1404 * @param msg the string message (or a key in the message catalog, if
1405 * this logger is a {@link
1406 * LoggerFinder#getLocalizedLogger(java.lang.String,
1407 * java.util.ResourceBundle, java.lang.Module) localized logger});
1408 * can be {@code null}.
1409 * @param thrown a {@code Throwable} associated with the log message;
1410 * can be {@code null}.
1411 *
1412 * @throws NullPointerException if {@code level} is {@code null}.
1413 */
1414 public default void log(Level level, String msg, Throwable thrown) {
1415 this.log(level, null, msg, thrown);
1416 }
1417
1418 /**
1419 * Logs a lazily supplied message associated with a given throwable.
1420 *
1421 * If the logger is currently enabled for the given log message level
1422 * then a message is logged that is the result produced by the
1423 * given supplier function. Otherwise, the supplier is not operated on.
1424 *
1425 * @implSpec When logging is enabled for the given level, the default
1426 * implementation for this method calls
1427 * {@code this.log(level, (ResourceBundle)null, msgSupplier.get(), thrown);}
1428 *
1429 * @param level one of the log message level identifiers.
1430 * @param msgSupplier a supplier function that produces a message.
1431 * @param thrown a {@code Throwable} associated with log message;
1432 * can be {@code null}.
1433 *
1434 * @throws NullPointerException if {@code level} is {@code null}, or
1435 * {@code msgSupplier} is {@code null}.
1436 */
1437 public default void log(Level level, Supplier<String> msgSupplier,
1438 Throwable thrown) {
1439 Objects.requireNonNull(msgSupplier);
1440 if (isLoggable(Objects.requireNonNull(level))) {
1441 this.log(level, null, msgSupplier.get(), thrown);
1442 }
1443 }
1444
1445 /**
1446 * Logs a message with an optional list of parameters.
1447 *
1448 * @implSpec The default implementation for this method calls
1449 * {@code this.log(level, (ResourceBundle)null, format, params);}
1450 *
1451 * @param level one of the log message level identifiers.
1452 * @param format the string message format in {@link
1453 * java.text.MessageFormat} format, (or a key in the message
1454 * catalog, if this logger is a {@link
1455 * LoggerFinder#getLocalizedLogger(java.lang.String,
1456 * java.util.ResourceBundle, java.lang.Module) localized logger});
1457 * can be {@code null}.
1458 * @param params an optional list of parameters to the message (may be
1459 * none).
1460 *
1461 * @throws NullPointerException if {@code level} is {@code null}.
1462 */
1463 public default void log(Level level, String format, Object... params) {
1464 this.log(level, null, format, params);
1465 }
1466
1467 /**
1468 * Logs a localized message associated with a given throwable.
1469 *
1470 * If the given resource bundle is non-{@code null}, the {@code msg}
1471 * string is localized using the given resource bundle.
1472 * Otherwise the {@code msg} string is not localized.
1473 *
1474 * @param level the log message level.
1475 * @param bundle a resource bundle to localize {@code msg}; can be
1476 * {@code null}.
1477 * @param msg the string message (or a key in the message catalog,
1478 * if {@code bundle} is not {@code null}); can be {@code null}.
1479 * @param thrown a {@code Throwable} associated with the log message;
1480 * can be {@code null}.
1481 *
1482 * @throws NullPointerException if {@code level} is {@code null}.
1483 */
1484 public void log(Level level, ResourceBundle bundle, String msg,
1485 Throwable thrown);
1486
1487 /**
1488 * Logs a message with resource bundle and an optional list of
1489 * parameters.
1490 *
1491 * If the given resource bundle is non-{@code null}, the {@code format}
1492 * string is localized using the given resource bundle.
1493 * Otherwise the {@code format} string is not localized.
1494 *
1495 * @param level the log message level.
1496 * @param bundle a resource bundle to localize {@code format}; can be
1497 * {@code null}.
1498 * @param format the string message format in {@link
1499 * java.text.MessageFormat} format, (or a key in the message
1500 * catalog if {@code bundle} is not {@code null}); can be {@code null}.
1501 * @param params an optional list of parameters to the message (may be
1502 * none).
1503 *
1504 * @throws NullPointerException if {@code level} is {@code null}.
1505 */
1506 public void log(Level level, ResourceBundle bundle, String format,
1507 Object... params);
1508 }
1509
1510 /**
1511 * The {@code LoggerFinder} service is responsible for creating, managing,
1512 * and configuring loggers to the underlying framework it uses.
1513 *
1514 * A logger finder is a concrete implementation of this class that has a
1515 * zero-argument constructor and implements the abstract methods defined
1516 * by this class.
1517 * The loggers returned from a logger finder are capable of routing log
1518 * messages to the logging backend this provider supports.
1519 * A given invocation of the Java Runtime maintains a single
1520 * system-wide LoggerFinder instance that is loaded as follows:
1521 * <ul>
1522 * <li>First it finds any custom {@code LoggerFinder} provider
1523 * using the {@link java.util.ServiceLoader} facility with the
1524 * {@linkplain ClassLoader#getSystemClassLoader() system class
1525 * loader}.</li>
1526 * <li>If no {@code LoggerFinder} provider is found, the system default
1527 * {@code LoggerFinder} implementation will be used.</li>
1528 * </ul>
1529 * <p>
1530 * An application can replace the logging backend
1531 * <i>even when the java.logging module is present</i>, by simply providing
1532 * and declaring an implementation of the {@link LoggerFinder} service.
1533 * <p>
1534 * <b>Default Implementation</b>
1535 * <p>
1536 * The system default {@code LoggerFinder} implementation uses
1537 * {@code java.util.logging} as the backend framework when the
1538 * {@code java.logging} module is present.
1539 * It returns a {@linkplain System.Logger logger} instance
1540 * that will route log messages to a {@link java.util.logging.Logger
1541 * java.util.logging.Logger}. Otherwise, if {@code java.logging} is not
1542 * present, the default implementation will return a simple logger
1543 * instance that will route log messages of {@code INFO} level and above to
1544 * the console ({@code System.err}).
1545 * <p>
1546 * <b>Logging Configuration</b>
1547 * <p>
1548 * {@linkplain Logger Logger} instances obtained from the
1549 * {@code LoggerFinder} factory methods are not directly configurable by
1550 * the application. Configuration is the responsibility of the underlying
1551 * logging backend, and usually requires using APIs specific to that backend.
1552 * <p>For the default {@code LoggerFinder} implementation
1553 * using {@code java.util.logging} as its backend, refer to
1554 * {@link java.util.logging java.util.logging} for logging configuration.
1555 * For the default {@code LoggerFinder} implementation returning simple loggers
1556 * when the {@code java.logging} module is absent, the configuration
1557 * is implementation dependent.
1558 * <p>
1559 * Usually an application that uses a logging framework will log messages
1560 * through a logger facade defined (or supported) by that framework.
1561 * Applications that wish to use an external framework should log
1562 * through the facade associated with that framework.
1563 * <p>
1564 * A system class that needs to log messages will typically obtain
1565 * a {@link System.Logger} instance to route messages to the logging
1566 * framework selected by the application.
1567 * <p>
1568 * Libraries and classes that only need loggers to produce log messages
1569 * should not attempt to configure loggers by themselves, as that
1570 * would make them dependent from a specific implementation of the
1571 * {@code LoggerFinder} service.
1572 * <p>
1573 * In addition, when a security manager is present, loggers provided to
1574 * system classes should not be directly configurable through the logging
1575 * backend without requiring permissions.
1576 * <br>
1577 * It is the responsibility of the provider of
1578 * the concrete {@code LoggerFinder} implementation to ensure that
1579 * these loggers are not configured by untrusted code without proper
1580 * permission checks, as configuration performed on such loggers usually
1581 * affects all applications in the same Java Runtime.
1582 * <p>
1583 * <b>Message Levels and Mapping to backend levels</b>
1584 * <p>
1585 * A logger finder is responsible for mapping from a {@code
1586 * System.Logger.Level} to a level supported by the logging backend it uses.
1587 * <br>The default LoggerFinder using {@code java.util.logging} as the backend
1588 * maps {@code System.Logger} levels to
1589 * {@linkplain java.util.logging.Level java.util.logging} levels
1590 * of corresponding severity - as described in {@link Logger.Level
1591 * Logger.Level}.
1592 *
1593 * @see java.lang.System
1594 * @see java.lang.System.Logger
1595 *
1596 * @since 9
1597 */
1598 public static abstract class LoggerFinder {
1599 /**
1600 * The {@code RuntimePermission("loggerFinder")} is
1601 * necessary to subclass and instantiate the {@code LoggerFinder} class,
1602 * as well as to obtain loggers from an instance of that class.
1603 */
1604 static final RuntimePermission LOGGERFINDER_PERMISSION =
1605 new RuntimePermission("loggerFinder");
1606
1607 /**
1608 * Creates a new instance of {@code LoggerFinder}.
1609 *
1610 * @implNote It is recommended that a {@code LoggerFinder} service
1611 * implementation does not perform any heavy initialization in its
1612 * constructor, in order to avoid possible risks of deadlock or class
1613 * loading cycles during the instantiation of the service provider.
1614 *
1615 * @throws SecurityException if a security manager is present and its
1616 * {@code checkPermission} method doesn't allow the
1617 * {@code RuntimePermission("loggerFinder")}.
1618 */
1619 protected LoggerFinder() {
1620 this(checkPermission());
1621 }
1622
1623 private LoggerFinder(Void unused) {
1624 // nothing to do.
1625 }
1626
1627 private static Void checkPermission() {
1628 @SuppressWarnings("removal")
1629 final SecurityManager sm = System.getSecurityManager();
1630 if (sm != null) {
1631 sm.checkPermission(LOGGERFINDER_PERMISSION);
1632 }
1633 return null;
1634 }
1635
1636 /**
1637 * Returns an instance of {@link Logger Logger}
1638 * for the given {@code module}.
1639 *
1640 * @param name the name of the logger.
1641 * @param module the module for which the logger is being requested.
1642 *
1643 * @return a {@link Logger logger} suitable for use within the given
1644 * module.
1645 * @throws NullPointerException if {@code name} is {@code null} or
1646 * {@code module} is {@code null}.
1647 * @throws SecurityException if a security manager is present and its
1648 * {@code checkPermission} method doesn't allow the
1649 * {@code RuntimePermission("loggerFinder")}.
1650 */
1651 public abstract Logger getLogger(String name, Module module);
1652
1653 /**
1654 * Returns a localizable instance of {@link Logger Logger}
1655 * for the given {@code module}.
1656 * The returned logger will use the provided resource bundle for
1657 * message localization.
1658 *
1659 * @implSpec By default, this method calls {@link
1660 * #getLogger(java.lang.String, java.lang.Module)
1661 * this.getLogger(name, module)} to obtain a logger, then wraps that
1662 * logger in a {@link Logger} instance where all methods that do not
1663 * take a {@link ResourceBundle} as parameter are redirected to one
1664 * which does - passing the given {@code bundle} for
1665 * localization. So for instance, a call to {@link
1666 * Logger#log(Logger.Level, String) Logger.log(Level.INFO, msg)}
1667 * will end up as a call to {@link
1668 * Logger#log(Logger.Level, ResourceBundle, String, Object...)
1669 * Logger.log(Level.INFO, bundle, msg, (Object[])null)} on the wrapped
1670 * logger instance.
1671 * Note however that by default, string messages returned by {@link
1672 * java.util.function.Supplier Supplier<String>} will not be
1673 * localized, as it is assumed that such strings are messages which are
1674 * already constructed, rather than keys in a resource bundle.
1675 * <p>
1676 * An implementation of {@code LoggerFinder} may override this method,
1677 * for example, when the underlying logging backend provides its own
1678 * mechanism for localizing log messages, then such a
1679 * {@code LoggerFinder} would be free to return a logger
1680 * that makes direct use of the mechanism provided by the backend.
1681 *
1682 * @param name the name of the logger.
1683 * @param bundle a resource bundle; can be {@code null}.
1684 * @param module the module for which the logger is being requested.
1685 * @return an instance of {@link Logger Logger} which will use the
1686 * provided resource bundle for message localization.
1687 *
1688 * @throws NullPointerException if {@code name} is {@code null} or
1689 * {@code module} is {@code null}.
1690 * @throws SecurityException if a security manager is present and its
1691 * {@code checkPermission} method doesn't allow the
1692 * {@code RuntimePermission("loggerFinder")}.
1693 */
1694 public Logger getLocalizedLogger(String name, ResourceBundle bundle,
1695 Module module) {
1696 return new LocalizedLoggerWrapper<>(getLogger(name, module), bundle);
1697 }
1698
1699 /**
1700 * Returns the {@code LoggerFinder} instance. There is one
1701 * single system-wide {@code LoggerFinder} instance in
1702 * the Java Runtime. See the class specification of how the
1703 * {@link LoggerFinder LoggerFinder} implementation is located and
1704 * loaded.
1705 *
1706 * @return the {@link LoggerFinder LoggerFinder} instance.
1707 * @throws SecurityException if a security manager is present and its
1708 * {@code checkPermission} method doesn't allow the
1709 * {@code RuntimePermission("loggerFinder")}.
1710 */
1711 public static LoggerFinder getLoggerFinder() {
1712 @SuppressWarnings("removal")
1713 final SecurityManager sm = System.getSecurityManager();
1714 if (sm != null) {
1715 sm.checkPermission(LOGGERFINDER_PERMISSION);
1716 }
1717 return accessProvider();
1718 }
1719
1720
1721 private static volatile LoggerFinder service;
1722 @SuppressWarnings("removal")
1723 static LoggerFinder accessProvider() {
1724 // We do not need to synchronize: LoggerFinderLoader will
1725 // always return the same instance, so if we don't have it,
1726 // just fetch it again.
1727 if (service == null) {
1728 PrivilegedAction<LoggerFinder> pa =
1729 () -> LoggerFinderLoader.getLoggerFinder();
1730 service = AccessController.doPrivileged(pa, null,
1731 LOGGERFINDER_PERMISSION);
1732 }
1733 return service;
1734 }
1735
1736 }
1737
1738
1739 /**
1740 * Returns an instance of {@link Logger Logger} for the caller's
1741 * use.
1742 *
1743 * @implSpec
1744 * Instances returned by this method route messages to loggers
1745 * obtained by calling {@link LoggerFinder#getLogger(java.lang.String,
1746 * java.lang.Module) LoggerFinder.getLogger(name, module)}, where
1747 * {@code module} is the caller's module.
1748 * In cases where {@code System.getLogger} is called from a context where
1749 * there is no caller frame on the stack (e.g when called directly
1750 * from a JNI attached thread), {@code IllegalCallerException} is thrown.
1751 * To obtain a logger in such a context, use an auxiliary class that will
1752 * implicitly be identified as the caller, or use the system {@link
1753 * LoggerFinder#getLoggerFinder() LoggerFinder} to obtain a logger instead.
1754 * Note that doing the latter may eagerly initialize the underlying
1755 * logging system.
1756 *
1757 * @apiNote
1758 * This method may defer calling the {@link
1759 * LoggerFinder#getLogger(java.lang.String, java.lang.Module)
1760 * LoggerFinder.getLogger} method to create an actual logger supplied by
1761 * the logging backend, for instance, to allow loggers to be obtained during
1762 * the system initialization time.
1763 *
1764 * @param name the name of the logger.
1765 * @return an instance of {@link Logger} that can be used by the calling
1766 * class.
1767 * @throws NullPointerException if {@code name} is {@code null}.
1768 * @throws IllegalCallerException if there is no Java caller frame on the
1769 * stack.
1770 *
1771 * @since 9
1772 */
1773 @CallerSensitive
1774 public static Logger getLogger(String name) {
1775 Objects.requireNonNull(name);
1776 final Class<?> caller = Reflection.getCallerClass();
1777 if (caller == null) {
1778 throw new IllegalCallerException("no caller frame");
1779 }
1780 return LazyLoggers.getLogger(name, caller.getModule());
1781 }
1782
1783 /**
1784 * Returns a localizable instance of {@link Logger
1785 * Logger} for the caller's use.
1786 * The returned logger will use the provided resource bundle for message
1787 * localization.
1788 *
1789 * @implSpec
1790 * The returned logger will perform message localization as specified
1791 * by {@link LoggerFinder#getLocalizedLogger(java.lang.String,
1792 * java.util.ResourceBundle, java.lang.Module)
1793 * LoggerFinder.getLocalizedLogger(name, bundle, module)}, where
1794 * {@code module} is the caller's module.
1795 * In cases where {@code System.getLogger} is called from a context where
1796 * there is no caller frame on the stack (e.g when called directly
1797 * from a JNI attached thread), {@code IllegalCallerException} is thrown.
1798 * To obtain a logger in such a context, use an auxiliary class that
1799 * will implicitly be identified as the caller, or use the system {@link
1800 * LoggerFinder#getLoggerFinder() LoggerFinder} to obtain a logger instead.
1801 * Note that doing the latter may eagerly initialize the underlying
1802 * logging system.
1803 *
1804 * @apiNote
1805 * This method is intended to be used after the system is fully initialized.
1806 * This method may trigger the immediate loading and initialization
1807 * of the {@link LoggerFinder} service, which may cause issues if the
1808 * Java Runtime is not ready to initialize the concrete service
1809 * implementation yet.
1810 * System classes which may be loaded early in the boot sequence and
1811 * need to log localized messages should create a logger using
1812 * {@link #getLogger(java.lang.String)} and then use the log methods that
1813 * take a resource bundle as parameter.
1814 *
1815 * @param name the name of the logger.
1816 * @param bundle a resource bundle.
1817 * @return an instance of {@link Logger} which will use the provided
1818 * resource bundle for message localization.
1819 * @throws NullPointerException if {@code name} is {@code null} or
1820 * {@code bundle} is {@code null}.
1821 * @throws IllegalCallerException if there is no Java caller frame on the
1822 * stack.
1823 *
1824 * @since 9
1825 */
1826 @SuppressWarnings("removal")
1827 @CallerSensitive
1828 public static Logger getLogger(String name, ResourceBundle bundle) {
1829 final ResourceBundle rb = Objects.requireNonNull(bundle);
1830 Objects.requireNonNull(name);
1831 final Class<?> caller = Reflection.getCallerClass();
1832 if (caller == null) {
1833 throw new IllegalCallerException("no caller frame");
1834 }
1835 final SecurityManager sm = System.getSecurityManager();
1836 // We don't use LazyLoggers if a resource bundle is specified.
1837 // Bootstrap sensitive classes in the JDK do not use resource bundles
1838 // when logging. This could be revisited later, if it needs to.
1839 if (sm != null) {
1840 final PrivilegedAction<Logger> pa =
1841 () -> LoggerFinder.accessProvider()
1842 .getLocalizedLogger(name, rb, caller.getModule());
1843 return AccessController.doPrivileged(pa, null,
1844 LoggerFinder.LOGGERFINDER_PERMISSION);
1845 }
1846 return LoggerFinder.accessProvider()
1847 .getLocalizedLogger(name, rb, caller.getModule());
1848 }
1849
1850 /**
1851 * Terminates the currently running Java Virtual Machine. The
1852 * argument serves as a status code; by convention, a nonzero status
1853 * code indicates abnormal termination.
1854 * <p>
1855 * This method calls the {@code exit} method in class
1856 * {@code Runtime}. This method never returns normally.
1857 * <p>
1858 * The call {@code System.exit(n)} is effectively equivalent to
1859 * the call:
1860 * <blockquote><pre>
1861 * Runtime.getRuntime().exit(n)
1862 * </pre></blockquote>
1863 *
1864 * @param status exit status.
1865 * @throws SecurityException
1866 * if a security manager exists and its {@code checkExit}
1867 * method doesn't allow exit with the specified status.
1868 * @see java.lang.Runtime#exit(int)
1869 */
1870 public static void exit(int status) {
1871 Runtime.getRuntime().exit(status);
1872 }
1873
1874 /**
1875 * Runs the garbage collector in the Java Virtual Machine.
1876 * <p>
1877 * Calling the {@code gc} method suggests that the Java Virtual Machine
1878 * expend effort toward recycling unused objects in order to
1879 * make the memory they currently occupy available for reuse
1880 * by the Java Virtual Machine.
1881 * When control returns from the method call, the Java Virtual Machine
1882 * has made a best effort to reclaim space from all unused objects.
1883 * There is no guarantee that this effort will recycle any particular
1884 * number of unused objects, reclaim any particular amount of space, or
1885 * complete at any particular time, if at all, before the method returns or ever.
1886 * There is also no guarantee that this effort will determine
1887 * the change of reachability in any particular number of objects,
1888 * or that any particular number of {@link java.lang.ref.Reference Reference}
1889 * objects will be cleared and enqueued.
1890 *
1891 * <p>
1892 * The call {@code System.gc()} is effectively equivalent to the
1893 * call:
1894 * <blockquote><pre>
1895 * Runtime.getRuntime().gc()
1896 * </pre></blockquote>
1897 *
1898 * @see java.lang.Runtime#gc()
1899 */
1900 public static void gc() {
1901 Runtime.getRuntime().gc();
1902 }
1903
1904 /**
1905 * Runs the finalization methods of any objects pending finalization.
1906 *
1907 * Calling this method suggests that the Java Virtual Machine expend
1908 * effort toward running the {@code finalize} methods of objects
1909 * that have been found to be discarded but whose {@code finalize}
1910 * methods have not yet been run. When control returns from the
1911 * method call, the Java Virtual Machine has made a best effort to
1912 * complete all outstanding finalizations.
1913 * <p>
1914 * The call {@code System.runFinalization()} is effectively
1915 * equivalent to the call:
1916 * <blockquote><pre>
1917 * Runtime.getRuntime().runFinalization()
1918 * </pre></blockquote>
1919 *
1920 * @deprecated Finalization has been deprecated for removal. See
1921 * {@link java.lang.Object#finalize} for background information and details
1922 * about migration options.
1923 * <p>
1924 * When running in a JVM in which finalization has been disabled or removed,
1925 * no objects will be pending finalization, so this method does nothing.
1926 *
1927 * @see java.lang.Runtime#runFinalization()
1928 * @jls 12.6 Finalization of Class Instances
1929 */
1930 @Deprecated(since="18", forRemoval=true)
1931 @SuppressWarnings("removal")
1932 public static void runFinalization() {
1933 Runtime.getRuntime().runFinalization();
1934 }
1935
1936 /**
1937 * Loads the native library specified by the filename argument. The filename
1938 * argument must be an absolute path name.
1939 *
1940 * If the filename argument, when stripped of any platform-specific library
1941 * prefix, path, and file extension, indicates a library whose name is,
1942 * for example, L, and a native library called L is statically linked
1943 * with the VM, then the JNI_OnLoad_L function exported by the library
1944 * is invoked rather than attempting to load a dynamic library.
1945 * A filename matching the argument does not have to exist in the
1946 * file system.
1947 * See the <a href="{@docRoot}/../specs/jni/index.html"> JNI Specification</a>
1948 * for more details.
1949 *
1950 * Otherwise, the filename argument is mapped to a native library image in
1951 * an implementation-dependent manner.
1952 *
1953 * <p>
1954 * The call {@code System.load(name)} is effectively equivalent
1955 * to the call:
1956 * <blockquote><pre>
1957 * Runtime.getRuntime().load(name)
1958 * </pre></blockquote>
1959 *
1960 * @param filename the file to load.
1961 * @throws SecurityException if a security manager exists and its
1962 * {@code checkLink} method doesn't allow
1963 * loading of the specified dynamic library
1964 * @throws UnsatisfiedLinkError if either the filename is not an
1965 * absolute path name, the native library is not statically
1966 * linked with the VM, or the library cannot be mapped to
1967 * a native library image by the host system.
1968 * @throws NullPointerException if {@code filename} is {@code null}
1969 * @see java.lang.Runtime#load(java.lang.String)
1970 * @see java.lang.SecurityManager#checkLink(java.lang.String)
1971 */
1972 @CallerSensitive
1973 public static void load(String filename) {
1974 Runtime.getRuntime().load0(Reflection.getCallerClass(), filename);
1975 }
1976
1977 /**
1978 * Loads the native library specified by the {@code libname}
1979 * argument. The {@code libname} argument must not contain any platform
1980 * specific prefix, file extension or path. If a native library
1981 * called {@code libname} is statically linked with the VM, then the
1982 * JNI_OnLoad_{@code libname} function exported by the library is invoked.
1983 * See the <a href="{@docRoot}/../specs/jni/index.html"> JNI Specification</a>
1984 * for more details.
1985 *
1986 * Otherwise, the libname argument is loaded from a system library
1987 * location and mapped to a native library image in an
1988 * implementation-dependent manner.
1989 * <p>
1990 * The call {@code System.loadLibrary(name)} is effectively
1991 * equivalent to the call
1992 * <blockquote><pre>
1993 * Runtime.getRuntime().loadLibrary(name)
1994 * </pre></blockquote>
1995 *
1996 * @param libname the name of the library.
1997 * @throws SecurityException if a security manager exists and its
1998 * {@code checkLink} method doesn't allow
1999 * loading of the specified dynamic library
2000 * @throws UnsatisfiedLinkError if either the libname argument
2001 * contains a file path, the native library is not statically
2002 * linked with the VM, or the library cannot be mapped to a
2003 * native library image by the host system.
2004 * @throws NullPointerException if {@code libname} is {@code null}
2005 * @see java.lang.Runtime#loadLibrary(java.lang.String)
2006 * @see java.lang.SecurityManager#checkLink(java.lang.String)
2007 */
2008 @CallerSensitive
2009 public static void loadLibrary(String libname) {
2010 Runtime.getRuntime().loadLibrary0(Reflection.getCallerClass(), libname);
2011 }
2012
2013 /**
2014 * Maps a library name into a platform-specific string representing
2015 * a native library.
2016 *
2017 * @param libname the name of the library.
2018 * @return a platform-dependent native library name.
2019 * @throws NullPointerException if {@code libname} is {@code null}
2020 * @see java.lang.System#loadLibrary(java.lang.String)
2021 * @see java.lang.ClassLoader#findLibrary(java.lang.String)
2022 * @since 1.2
2023 */
2024 public static native String mapLibraryName(String libname);
2025
2026 /**
2027 * Create PrintStream for stdout/err based on encoding.
2028 */
2029 private static PrintStream newPrintStream(FileOutputStream fos, String enc) {
2030 if (enc != null) {
2031 try {
2032 return new PrintStream(new BufferedOutputStream(fos, 128), true, enc);
2033 } catch (UnsupportedEncodingException uee) {}
2034 }
2035 return new PrintStream(new BufferedOutputStream(fos, 128), true);
2036 }
2037
2038 /**
2039 * Logs an exception/error at initialization time to stdout or stderr.
2040 *
2041 * @param printToStderr to print to stderr rather than stdout
2042 * @param printStackTrace to print the stack trace
2043 * @param msg the message to print before the exception, can be {@code null}
2044 * @param e the exception or error
2045 */
2046 private static void logInitException(boolean printToStderr,
2047 boolean printStackTrace,
2048 String msg,
2049 Throwable e) {
2050 if (VM.initLevel() < 1) {
2051 throw new InternalError("system classes not initialized");
2052 }
2053 PrintStream log = (printToStderr) ? err : out;
2054 if (msg != null) {
2055 log.println(msg);
2056 }
2057 if (printStackTrace) {
2058 e.printStackTrace(log);
2059 } else {
2060 log.println(e);
2061 for (Throwable suppressed : e.getSuppressed()) {
2062 log.println("Suppressed: " + suppressed);
2063 }
2064 Throwable cause = e.getCause();
2065 if (cause != null) {
2066 log.println("Caused by: " + cause);
2067 }
2068 }
2069 }
2070
2071 /**
2072 * Create the Properties object from a map - masking out system properties
2073 * that are not intended for public access.
2074 */
2075 private static Properties createProperties(Map<String, String> initialProps) {
2076 Properties properties = new Properties(initialProps.size());
2077 for (var entry : initialProps.entrySet()) {
2078 String prop = entry.getKey();
2079 switch (prop) {
2080 // Do not add private system properties to the Properties
2081 case "sun.nio.MaxDirectMemorySize":
2082 case "sun.nio.PageAlignDirectMemory":
2083 // used by java.lang.Integer.IntegerCache
2084 case "java.lang.Integer.IntegerCache.high":
2085 // used by sun.launcher.LauncherHelper
2086 case "sun.java.launcher.diag":
2087 // used by jdk.internal.loader.ClassLoaders
2088 case "jdk.boot.class.path.append":
2089 break;
2090 default:
2091 properties.put(prop, entry.getValue());
2092 }
2093 }
2094 return properties;
2095 }
2096
2097 /**
2098 * Initialize the system class. Called after thread initialization.
2099 */
2100 private static void initPhase1() {
2101
2102 // register the shared secrets - do this first, since SystemProps.initProperties
2103 // might initialize CharsetDecoders that rely on it
2104 setJavaLangAccess();
2105
2106 // VM might invoke JNU_NewStringPlatform() to set those encoding
2107 // sensitive properties (user.home, user.name, boot.class.path, etc.)
2108 // during "props" initialization.
2109 // The charset is initialized in System.c and does not depend on the Properties.
2110 Map<String, String> tempProps = SystemProps.initProperties();
2111 VersionProps.init(tempProps);
2112
2113 // There are certain system configurations that may be controlled by
2114 // VM options such as the maximum amount of direct memory and
2115 // Integer cache size used to support the object identity semantics
2116 // of autoboxing. Typically, the library will obtain these values
2117 // from the properties set by the VM. If the properties are for
2118 // internal implementation use only, these properties should be
2119 // masked from the system properties.
2120 //
2121 // Save a private copy of the system properties object that
2122 // can only be accessed by the internal implementation.
2123 VM.saveProperties(tempProps);
2124 props = createProperties(tempProps);
2125
2126 StaticProperty.javaHome(); // Load StaticProperty to cache the property values
2127
2128 lineSeparator = props.getProperty("line.separator");
2129
2130 FileInputStream fdIn = new FileInputStream(FileDescriptor.in);
2131 FileOutputStream fdOut = new FileOutputStream(FileDescriptor.out);
2132 FileOutputStream fdErr = new FileOutputStream(FileDescriptor.err);
2133 setIn0(new BufferedInputStream(fdIn));
2134 // sun.stdout/err.encoding are set when the VM is associated with the terminal,
2135 // thus they are equivalent to Console.charset(), otherwise the encoding
2136 // defaults to native.encoding
2137 setOut0(newPrintStream(fdOut, props.getProperty("sun.stdout.encoding", StaticProperty.nativeEncoding())));
2138 setErr0(newPrintStream(fdErr, props.getProperty("sun.stderr.encoding", StaticProperty.nativeEncoding())));
2139
2140 // Setup Java signal handlers for HUP, TERM, and INT (where available).
2141 Terminator.setup();
2142
2143 // Initialize any miscellaneous operating system settings that need to be
2144 // set for the class libraries. Currently this is no-op everywhere except
2145 // for Windows where the process-wide error mode is set before the java.io
2146 // classes are used.
2147 VM.initializeOSEnvironment();
2148
2149 // The main thread is not added to its thread group in the same
2150 // way as other threads; we must do it ourselves here.
2151 Thread current = Thread.currentThread();
2152 current.getThreadGroup().add(current);
2153
2154
2155 // Subsystems that are invoked during initialization can invoke
2156 // VM.isBooted() in order to avoid doing things that should
2157 // wait until the VM is fully initialized. The initialization level
2158 // is incremented from 0 to 1 here to indicate the first phase of
2159 // initialization has completed.
2160 // IMPORTANT: Ensure that this remains the last initialization action!
2161 VM.initLevel(1);
2162 }
2163
2164 // @see #initPhase2()
2165 static ModuleLayer bootLayer;
2166
2167 /*
2168 * Invoked by VM. Phase 2 module system initialization.
2169 * Only classes in java.base can be loaded in this phase.
2170 *
2171 * @param printToStderr print exceptions to stderr rather than stdout
2172 * @param printStackTrace print stack trace when exception occurs
2173 *
2174 * @return JNI_OK for success, JNI_ERR for failure
2175 */
2176 private static int initPhase2(boolean printToStderr, boolean printStackTrace) {
2177
2178 try {
2179 bootLayer = ModuleBootstrap.boot();
2180 } catch (Exception | Error e) {
2181 logInitException(printToStderr, printStackTrace,
2182 "Error occurred during initialization of boot layer", e);
2183 return -1; // JNI_ERR
2184 }
2185
2186 // module system initialized
2187 VM.initLevel(2);
2188
2189 return 0; // JNI_OK
2190 }
2191
2192 /*
2193 * Invoked by VM. Phase 3 is the final system initialization:
2194 * 1. eagerly initialize bootstrap method factories that might interact
2195 * negatively with custom security managers and custom class loaders
2196 * 2. set security manager
2197 * 3. set system class loader
2198 * 4. set TCCL
2199 *
2200 * This method must be called after the module system initialization.
2201 * The security manager and system class loader may be a custom class from
2202 * the application classpath or modulepath.
2203 */
2204 @SuppressWarnings("removal")
2205 private static void initPhase3() {
2206
2207 // Initialize the StringConcatFactory eagerly to avoid potential
2208 // bootstrap circularity issues that could be caused by a custom
2209 // SecurityManager
2210 Unsafe.getUnsafe().ensureClassInitialized(StringConcatFactory.class);
2211
2212 String smProp = System.getProperty("java.security.manager");
2213 boolean needWarning = false;
2214 if (smProp != null) {
2215 switch (smProp) {
2216 case "disallow":
2217 allowSecurityManager = NEVER;
2218 break;
2219 case "allow":
2220 allowSecurityManager = MAYBE;
2221 break;
2222 case "":
2223 case "default":
2224 implSetSecurityManager(new SecurityManager());
2225 allowSecurityManager = MAYBE;
2226 needWarning = true;
2227 break;
2228 default:
2229 try {
2230 ClassLoader cl = ClassLoader.getBuiltinAppClassLoader();
2231 Class<?> c = Class.forName(smProp, false, cl);
2232 Constructor<?> ctor = c.getConstructor();
2233 // Must be a public subclass of SecurityManager with
2234 // a public no-arg constructor
2235 if (!SecurityManager.class.isAssignableFrom(c) ||
2236 !Modifier.isPublic(c.getModifiers()) ||
2237 !Modifier.isPublic(ctor.getModifiers())) {
2238 throw new Error("Could not create SecurityManager: "
2239 + ctor.toString());
2240 }
2241 // custom security manager may be in non-exported package
2242 ctor.setAccessible(true);
2243 SecurityManager sm = (SecurityManager) ctor.newInstance();
2244 implSetSecurityManager(sm);
2245 needWarning = true;
2246 } catch (Exception e) {
2247 throw new InternalError("Could not create SecurityManager", e);
2248 }
2249 allowSecurityManager = MAYBE;
2250 }
2251 } else {
2252 allowSecurityManager = NEVER;
2253 }
2254
2255 if (needWarning) {
2256 System.err.println("""
2257 WARNING: A command line option has enabled the Security Manager
2258 WARNING: The Security Manager is deprecated and will be removed in a future release""");
2259 }
2260
2261 initialErrStream = System.err;
2262
2263 // initializing the system class loader
2264 VM.initLevel(3);
2265
2266 // system class loader initialized
2267 ClassLoader scl = ClassLoader.initSystemClassLoader();
2268
2269 // set TCCL
2270 Thread.currentThread().setContextClassLoader(scl);
2271
2272 // system is fully initialized
2273 VM.initLevel(4);
2274 }
2275
2276 private static void setJavaLangAccess() {
2277 // Allow privileged classes outside of java.lang
2278 SharedSecrets.setJavaLangAccess(new JavaLangAccess() {
2279 public List<Method> getDeclaredPublicMethods(Class<?> klass, String name, Class<?>... parameterTypes) {
2280 return klass.getDeclaredPublicMethods(name, parameterTypes);
2281 }
2282 public jdk.internal.reflect.ConstantPool getConstantPool(Class<?> klass) {
2283 return klass.getConstantPool();
2284 }
2285 public boolean casAnnotationType(Class<?> klass, AnnotationType oldType, AnnotationType newType) {
2286 return klass.casAnnotationType(oldType, newType);
2287 }
2288 public AnnotationType getAnnotationType(Class<?> klass) {
2289 return klass.getAnnotationType();
2290 }
2291 public Map<Class<? extends Annotation>, Annotation> getDeclaredAnnotationMap(Class<?> klass) {
2292 return klass.getDeclaredAnnotationMap();
2293 }
2294 public byte[] getRawClassAnnotations(Class<?> klass) {
2295 return klass.getRawAnnotations();
2296 }
2297 public byte[] getRawClassTypeAnnotations(Class<?> klass) {
2298 return klass.getRawTypeAnnotations();
2299 }
2300 public byte[] getRawExecutableTypeAnnotations(Executable executable) {
2301 return Class.getExecutableTypeAnnotationBytes(executable);
2302 }
2303 public <E extends Enum<E>>
2304 E[] getEnumConstantsShared(Class<E> klass) {
2305 return klass.getEnumConstantsShared();
2306 }
2307 public void blockedOn(Interruptible b) {
2308 Thread.blockedOn(b);
2309 }
2310 public void registerShutdownHook(int slot, boolean registerShutdownInProgress, Runnable hook) {
2311 Shutdown.add(slot, registerShutdownInProgress, hook);
2312 }
2313 public Thread newThreadWithAcc(Runnable target, @SuppressWarnings("removal") AccessControlContext acc) {
2314 return new Thread(target, acc);
2315 }
2316 @SuppressWarnings("removal")
2317 public void invokeFinalize(Object o) throws Throwable {
2318 o.finalize();
2319 }
2320 public ConcurrentHashMap<?, ?> createOrGetClassLoaderValueMap(ClassLoader cl) {
2321 return cl.createOrGetClassLoaderValueMap();
2322 }
2323 public Class<?> defineClass(ClassLoader loader, String name, byte[] b, ProtectionDomain pd, String source) {
2324 return ClassLoader.defineClass1(loader, name, b, 0, b.length, pd, source);
2325 }
2326 public Class<?> defineClass(ClassLoader loader, Class<?> lookup, String name, byte[] b, ProtectionDomain pd,
2327 boolean initialize, int flags, Object classData) {
2328 return ClassLoader.defineClass0(loader, lookup, name, b, 0, b.length, pd, initialize, flags, classData);
2329 }
2330 public Class<?> findBootstrapClassOrNull(String name) {
2331 return ClassLoader.findBootstrapClassOrNull(name);
2332 }
2333 public Package definePackage(ClassLoader cl, String name, Module module) {
2334 return cl.definePackage(name, module);
2335 }
2336 public String fastUUID(long lsb, long msb) {
2337 return Long.fastUUID(lsb, msb);
2338 }
2339 @SuppressWarnings("removal")
2340 public void addNonExportedPackages(ModuleLayer layer) {
2341 SecurityManager.addNonExportedPackages(layer);
2342 }
2343 @SuppressWarnings("removal")
2344 public void invalidatePackageAccessCache() {
2345 SecurityManager.invalidatePackageAccessCache();
2346 }
2347 public Module defineModule(ClassLoader loader,
2348 ModuleDescriptor descriptor,
2349 URI uri) {
2350 return new Module(null, loader, descriptor, uri);
2351 }
2352 public Module defineUnnamedModule(ClassLoader loader) {
2353 return new Module(loader);
2354 }
2355 public void addReads(Module m1, Module m2) {
2356 m1.implAddReads(m2);
2357 }
2358 public void addReadsAllUnnamed(Module m) {
2359 m.implAddReadsAllUnnamed();
2360 }
2361 public void addExports(Module m, String pn) {
2362 m.implAddExports(pn);
2363 }
2364 public void addExports(Module m, String pn, Module other) {
2365 m.implAddExports(pn, other);
2366 }
2367 public void addExportsToAllUnnamed(Module m, String pn) {
2368 m.implAddExportsToAllUnnamed(pn);
2369 }
2370 public void addOpens(Module m, String pn, Module other) {
2371 m.implAddOpens(pn, other);
2372 }
2373 public void addOpensToAllUnnamed(Module m, String pn) {
2374 m.implAddOpensToAllUnnamed(pn);
2375 }
2376 public void addOpensToAllUnnamed(Module m, Set<String> concealedPackages, Set<String> exportedPackages) {
2377 m.implAddOpensToAllUnnamed(concealedPackages, exportedPackages);
2378 }
2379 public void addUses(Module m, Class<?> service) {
2380 m.implAddUses(service);
2381 }
2382 public boolean isReflectivelyExported(Module m, String pn, Module other) {
2383 return m.isReflectivelyExported(pn, other);
2384 }
2385 public boolean isReflectivelyOpened(Module m, String pn, Module other) {
2386 return m.isReflectivelyOpened(pn, other);
2387 }
2388 public Module addEnableNativeAccess(Module m) {
2389 return m.implAddEnableNativeAccess();
2390 }
2391 public void addEnableNativeAccessAllUnnamed() {
2392 Module.implAddEnableNativeAccessAllUnnamed();
2393 }
2394 public boolean isEnableNativeAccess(Module m) {
2395 return m.implIsEnableNativeAccess();
2396 }
2397 public ServicesCatalog getServicesCatalog(ModuleLayer layer) {
2398 return layer.getServicesCatalog();
2399 }
2400 public void bindToLoader(ModuleLayer layer, ClassLoader loader) {
2401 layer.bindToLoader(loader);
2402 }
2403 public Stream<ModuleLayer> layers(ModuleLayer layer) {
2404 return layer.layers();
2405 }
2406 public Stream<ModuleLayer> layers(ClassLoader loader) {
2407 return ModuleLayer.layers(loader);
2408 }
2409
2410 public String newStringNoRepl(byte[] bytes, Charset cs) throws CharacterCodingException {
2411 return String.newStringNoRepl(bytes, cs);
2412 }
2413
2414 public byte[] getBytesNoRepl(String s, Charset cs) throws CharacterCodingException {
2415 return String.getBytesNoRepl(s, cs);
2416 }
2417
2418 public String newStringUTF8NoRepl(byte[] bytes, int off, int len) {
2419 return String.newStringUTF8NoRepl(bytes, off, len);
2420 }
2421
2422 public byte[] getBytesUTF8NoRepl(String s) {
2423 return String.getBytesUTF8NoRepl(s);
2424 }
2425
2426 public void inflateBytesToChars(byte[] src, int srcOff, char[] dst, int dstOff, int len) {
2427 StringLatin1.inflate(src, srcOff, dst, dstOff, len);
2428 }
2429
2430 public int decodeASCII(byte[] src, int srcOff, char[] dst, int dstOff, int len) {
2431 return String.decodeASCII(src, srcOff, dst, dstOff, len);
2432 }
2433
2434 public int encodeASCII(char[] src, int srcOff, byte[] dst, int dstOff, int len) {
2435 return StringCoding.implEncodeAsciiArray(src, srcOff, dst, dstOff, len);
2436 }
2437
2438 public void setCause(Throwable t, Throwable cause) {
2439 t.setCause(cause);
2440 }
2441
2442 public ProtectionDomain protectionDomain(Class<?> c) {
2443 return c.protectionDomain();
2444 }
2445
2446 public MethodHandle stringConcatHelper(String name, MethodType methodType) {
2447 return StringConcatHelper.lookupStatic(name, methodType);
2448 }
2449
2450 public long stringConcatInitialCoder() {
2451 return StringConcatHelper.initialCoder();
2452 }
2453
2454 public long stringConcatMix(long lengthCoder, String constant) {
2455 return StringConcatHelper.mix(lengthCoder, constant);
2456 }
2457
2458 public String join(String prefix, String suffix, String delimiter, String[] elements, int size) {
2459 return String.join(prefix, suffix, delimiter, elements, size);
2460 }
2461
2462 public Object classData(Class<?> c) {
2463 return c.getClassData();
2464 }
2465
2466 @Override
2467 public long findNative(ClassLoader loader, String entry) {
2468 return ClassLoader.findNative(loader, entry);
2469 }
2470
2471 @Override
2472 public void exit(int statusCode) {
2473 Shutdown.exit(statusCode);
2474 }
2475 });
2476 }
2477 }