1 /*
2 * Copyright (c) 1995, 2006, 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
26 package java.lang;
27
28 import java.io;
29 import java.util.StringTokenizer;
30
31 /**
32 * Every Java application has a single instance of class
33 * <code>Runtime</code> that allows the application to interface with
34 * the environment in which the application is running. The current
35 * runtime can be obtained from the <code>getRuntime</code> method.
36 * <p>
37 * An application cannot create its own instance of this class.
38 *
39 * @author unascribed
40 * @see java.lang.Runtime#getRuntime()
41 * @since JDK1.0
42 */
43
44 public class Runtime {
45 private static Runtime currentRuntime = new Runtime();
46
47 /**
48 * Returns the runtime object associated with the current Java application.
49 * Most of the methods of class <code>Runtime</code> are instance
50 * methods and must be invoked with respect to the current runtime object.
51 *
52 * @return the <code>Runtime</code> object associated with the current
53 * Java application.
54 */
55 public static Runtime getRuntime() {
56 return currentRuntime;
57 }
58
59 /** Don't let anyone else instantiate this class */
60 private Runtime() {}
61
62 /**
63 * Terminates the currently running Java virtual machine by initiating its
64 * shutdown sequence. This method never returns normally. The argument
65 * serves as a status code; by convention, a nonzero status code indicates
66 * abnormal termination.
67 *
68 * <p> The virtual machine's shutdown sequence consists of two phases. In
69 * the first phase all registered {@link #addShutdownHook shutdown hooks},
70 * if any, are started in some unspecified order and allowed to run
71 * concurrently until they finish. In the second phase all uninvoked
72 * finalizers are run if {@link #runFinalizersOnExit finalization-on-exit}
73 * has been enabled. Once this is done the virtual machine {@link #halt
74 * halts}.
75 *
76 * <p> If this method is invoked after the virtual machine has begun its
77 * shutdown sequence then if shutdown hooks are being run this method will
78 * block indefinitely. If shutdown hooks have already been run and on-exit
79 * finalization has been enabled then this method halts the virtual machine
80 * with the given status code if the status is nonzero; otherwise, it
81 * blocks indefinitely.
82 *
83 * <p> The <tt>{@link System#exit(int) System.exit}</tt> method is the
84 * conventional and convenient means of invoking this method. <p>
85 *
86 * @param status
87 * Termination status. By convention, a nonzero status code
88 * indicates abnormal termination.
89 *
90 * @throws SecurityException
91 * If a security manager is present and its <tt>{@link
92 * SecurityManager#checkExit checkExit}</tt> method does not permit
93 * exiting with the specified status
94 *
95 * @see java.lang.SecurityException
96 * @see java.lang.SecurityManager#checkExit(int)
97 * @see #addShutdownHook
98 * @see #removeShutdownHook
99 * @see #runFinalizersOnExit
100 * @see #halt(int)
101 */
102 public void exit(int status) {
103 SecurityManager security = System.getSecurityManager();
104 if (security != null) {
105 security.checkExit(status);
106 }
107 Shutdown.exit(status);
108 }
109
110 /**
111 * Registers a new virtual-machine shutdown hook.
112 *
113 * <p> The Java virtual machine <i>shuts down</i> in response to two kinds
114 * of events:
115 *
116 * <ul>
117 *
118 * <p> <li> The program <i>exits</i> normally, when the last non-daemon
119 * thread exits or when the <tt>{@link #exit exit}</tt> (equivalently,
120 * <tt>{@link System#exit(int) System.exit}</tt>) method is invoked, or
121 *
122 * <p> <li> The virtual machine is <i>terminated</i> in response to a
123 * user interrupt, such as typing <tt>^C</tt>, or a system-wide event,
124 * such as user logoff or system shutdown.
125 *
126 * </ul>
127 *
128 * <p> A <i>shutdown hook</i> is simply an initialized but unstarted
129 * thread. When the virtual machine begins its shutdown sequence it will
130 * start all registered shutdown hooks in some unspecified order and let
131 * them run concurrently. When all the hooks have finished it will then
132 * run all uninvoked finalizers if finalization-on-exit has been enabled.
133 * Finally, the virtual machine will halt. Note that daemon threads will
134 * continue to run during the shutdown sequence, as will non-daemon threads
135 * if shutdown was initiated by invoking the <tt>{@link #exit exit}</tt>
136 * method.
137 *
138 * <p> Once the shutdown sequence has begun it can be stopped only by
139 * invoking the <tt>{@link #halt halt}</tt> method, which forcibly
140 * terminates the virtual machine.
141 *
142 * <p> Once the shutdown sequence has begun it is impossible to register a
143 * new shutdown hook or de-register a previously-registered hook.
144 * Attempting either of these operations will cause an
145 * <tt>{@link IllegalStateException}</tt> to be thrown.
146 *
147 * <p> Shutdown hooks run at a delicate time in the life cycle of a virtual
148 * machine and should therefore be coded defensively. They should, in
149 * particular, be written to be thread-safe and to avoid deadlocks insofar
150 * as possible. They should also not rely blindly upon services that may
151 * have registered their own shutdown hooks and therefore may themselves in
152 * the process of shutting down. Attempts to use other thread-based
153 * services such as the AWT event-dispatch thread, for example, may lead to
154 * deadlocks.
155 *
156 * <p> Shutdown hooks should also finish their work quickly. When a
157 * program invokes <tt>{@link #exit exit}</tt> the expectation is
158 * that the virtual machine will promptly shut down and exit. When the
159 * virtual machine is terminated due to user logoff or system shutdown the
160 * underlying operating system may only allow a fixed amount of time in
161 * which to shut down and exit. It is therefore inadvisable to attempt any
162 * user interaction or to perform a long-running computation in a shutdown
163 * hook.
164 *
165 * <p> Uncaught exceptions are handled in shutdown hooks just as in any
166 * other thread, by invoking the <tt>{@link ThreadGroup#uncaughtException
167 * uncaughtException}</tt> method of the thread's <tt>{@link
168 * ThreadGroup}</tt> object. The default implementation of this method
169 * prints the exception's stack trace to <tt>{@link System#err}</tt> and
170 * terminates the thread; it does not cause the virtual machine to exit or
171 * halt.
172 *
173 * <p> In rare circumstances the virtual machine may <i>abort</i>, that is,
174 * stop running without shutting down cleanly. This occurs when the
175 * virtual machine is terminated externally, for example with the
176 * <tt>SIGKILL</tt> signal on Unix or the <tt>TerminateProcess</tt> call on
177 * Microsoft Windows. The virtual machine may also abort if a native
178 * method goes awry by, for example, corrupting internal data structures or
179 * attempting to access nonexistent memory. If the virtual machine aborts
180 * then no guarantee can be made about whether or not any shutdown hooks
181 * will be run. <p>
182 *
183 * @param hook
184 * An initialized but unstarted <tt>{@link Thread}</tt> object
185 *
186 * @throws IllegalArgumentException
187 * If the specified hook has already been registered,
188 * or if it can be determined that the hook is already running or
189 * has already been run
190 *
191 * @throws IllegalStateException
192 * If the virtual machine is already in the process
193 * of shutting down
194 *
195 * @throws SecurityException
196 * If a security manager is present and it denies
197 * <tt>{@link RuntimePermission}("shutdownHooks")</tt>
198 *
199 * @see #removeShutdownHook
200 * @see #halt(int)
201 * @see #exit(int)
202 * @since 1.3
203 */
204 public void addShutdownHook(Thread hook) {
205 SecurityManager sm = System.getSecurityManager();
206 if (sm != null) {
207 sm.checkPermission(new RuntimePermission("shutdownHooks"));
208 }
209 ApplicationShutdownHooks.add(hook);
210 }
211
212 /**
213 * De-registers a previously-registered virtual-machine shutdown hook. <p>
214 *
215 * @param hook the hook to remove
216 * @return <tt>true</tt> if the specified hook had previously been
217 * registered and was successfully de-registered, <tt>false</tt>
218 * otherwise.
219 *
220 * @throws IllegalStateException
221 * If the virtual machine is already in the process of shutting
222 * down
223 *
224 * @throws SecurityException
225 * If a security manager is present and it denies
226 * <tt>{@link RuntimePermission}("shutdownHooks")</tt>
227 *
228 * @see #addShutdownHook
229 * @see #exit(int)
230 * @since 1.3
231 */
232 public boolean removeShutdownHook(Thread hook) {
233 SecurityManager sm = System.getSecurityManager();
234 if (sm != null) {
235 sm.checkPermission(new RuntimePermission("shutdownHooks"));
236 }
237 return ApplicationShutdownHooks.remove(hook);
238 }
239
240 /**
241 * Forcibly terminates the currently running Java virtual machine. This
242 * method never returns normally.
243 *
244 * <p> This method should be used with extreme caution. Unlike the
245 * <tt>{@link #exit exit}</tt> method, this method does not cause shutdown
246 * hooks to be started and does not run uninvoked finalizers if
247 * finalization-on-exit has been enabled. If the shutdown sequence has
248 * already been initiated then this method does not wait for any running
249 * shutdown hooks or finalizers to finish their work. <p>
250 *
251 * @param status
252 * Termination status. By convention, a nonzero status code
253 * indicates abnormal termination. If the <tt>{@link Runtime#exit
254 * exit}</tt> (equivalently, <tt>{@link System#exit(int)
255 * System.exit}</tt>) method has already been invoked then this
256 * status code will override the status code passed to that method.
257 *
258 * @throws SecurityException
259 * If a security manager is present and its <tt>{@link
260 * SecurityManager#checkExit checkExit}</tt> method does not permit
261 * an exit with the specified status
262 *
263 * @see #exit
264 * @see #addShutdownHook
265 * @see #removeShutdownHook
266 * @since 1.3
267 */
268 public void halt(int status) {
269 SecurityManager sm = System.getSecurityManager();
270 if (sm != null) {
271 sm.checkExit(status);
272 }
273 Shutdown.halt(status);
274 }
275
276 /**
277 * Enable or disable finalization on exit; doing so specifies that the
278 * finalizers of all objects that have finalizers that have not yet been
279 * automatically invoked are to be run before the Java runtime exits.
280 * By default, finalization on exit is disabled.
281 *
282 * <p>If there is a security manager,
283 * its <code>checkExit</code> method is first called
284 * with 0 as its argument to ensure the exit is allowed.
285 * This could result in a SecurityException.
286 *
287 * @param value true to enable finalization on exit, false to disable
288 * @deprecated This method is inherently unsafe. It may result in
289 * finalizers being called on live objects while other threads are
290 * concurrently manipulating those objects, resulting in erratic
291 * behavior or deadlock.
292 *
293 * @throws SecurityException
294 * if a security manager exists and its <code>checkExit</code>
295 * method doesn't allow the exit.
296 *
297 * @see java.lang.Runtime#exit(int)
298 * @see java.lang.Runtime#gc()
299 * @see java.lang.SecurityManager#checkExit(int)
300 * @since JDK1.1
301 */
302 @Deprecated
303 public static void runFinalizersOnExit(boolean value) {
304 SecurityManager security = System.getSecurityManager();
305 if (security != null) {
306 try {
307 security.checkExit(0);
308 } catch (SecurityException e) {
309 throw new SecurityException("runFinalizersOnExit");
310 }
311 }
312 Shutdown.setRunFinalizersOnExit(value);
313 }
314
315 /**
316 * Executes the specified string command in a separate process.
317 *
318 * <p>This is a convenience method. An invocation of the form
319 * <tt>exec(command)</tt>
320 * behaves in exactly the same way as the invocation
321 * <tt>{@link #exec(String, String[], File) exec}(command, null, null)</tt>.
322 *
323 * @param command a specified system command.
324 *
325 * @return A new {@link Process} object for managing the subprocess
326 *
327 * @throws SecurityException
328 * If a security manager exists and its
329 * {@link SecurityManager#checkExec checkExec}
330 * method doesn't allow creation of the subprocess
331 *
332 * @throws IOException
333 * If an I/O error occurs
334 *
335 * @throws NullPointerException
336 * If <code>command</code> is <code>null</code>
337 *
338 * @throws IllegalArgumentException
339 * If <code>command</code> is empty
340 *
341 * @see #exec(String[], String[], File)
342 * @see ProcessBuilder
343 */
344 public Process exec(String command) throws IOException {
345 return exec(command, null, null);
346 }
347
348 /**
349 * Executes the specified string command in a separate process with the
350 * specified environment.
351 *
352 * <p>This is a convenience method. An invocation of the form
353 * <tt>exec(command, envp)</tt>
354 * behaves in exactly the same way as the invocation
355 * <tt>{@link #exec(String, String[], File) exec}(command, envp, null)</tt>.
356 *
357 * @param command a specified system command.
358 *
359 * @param envp array of strings, each element of which
360 * has environment variable settings in the format
361 * <i>name</i>=<i>value</i>, or
362 * <tt>null</tt> if the subprocess should inherit
363 * the environment of the current process.
364 *
365 * @return A new {@link Process} object for managing the subprocess
366 *
367 * @throws SecurityException
368 * If a security manager exists and its
369 * {@link SecurityManager#checkExec checkExec}
370 * method doesn't allow creation of the subprocess
371 *
372 * @throws IOException
373 * If an I/O error occurs
374 *
375 * @throws NullPointerException
376 * If <code>command</code> is <code>null</code>,
377 * or one of the elements of <code>envp</code> is <code>null</code>
378 *
379 * @throws IllegalArgumentException
380 * If <code>command</code> is empty
381 *
382 * @see #exec(String[], String[], File)
383 * @see ProcessBuilder
384 */
385 public Process exec(String command, String[] envp) throws IOException {
386 return exec(command, envp, null);
387 }
388
389 /**
390 * Executes the specified string command in a separate process with the
391 * specified environment and working directory.
392 *
393 * <p>This is a convenience method. An invocation of the form
394 * <tt>exec(command, envp, dir)</tt>
395 * behaves in exactly the same way as the invocation
396 * <tt>{@link #exec(String[], String[], File) exec}(cmdarray, envp, dir)</tt>,
397 * where <code>cmdarray</code> is an array of all the tokens in
398 * <code>command</code>.
399 *
400 * <p>More precisely, the <code>command</code> string is broken
401 * into tokens using a {@link StringTokenizer} created by the call
402 * <code>new {@link StringTokenizer}(command)</code> with no
403 * further modification of the character categories. The tokens
404 * produced by the tokenizer are then placed in the new string
405 * array <code>cmdarray</code>, in the same order.
406 *
407 * @param command a specified system command.
408 *
409 * @param envp array of strings, each element of which
410 * has environment variable settings in the format
411 * <i>name</i>=<i>value</i>, or
412 * <tt>null</tt> if the subprocess should inherit
413 * the environment of the current process.
414 *
415 * @param dir the working directory of the subprocess, or
416 * <tt>null</tt> if the subprocess should inherit
417 * the working directory of the current process.
418 *
419 * @return A new {@link Process} object for managing the subprocess
420 *
421 * @throws SecurityException
422 * If a security manager exists and its
423 * {@link SecurityManager#checkExec checkExec}
424 * method doesn't allow creation of the subprocess
425 *
426 * @throws IOException
427 * If an I/O error occurs
428 *
429 * @throws NullPointerException
430 * If <code>command</code> is <code>null</code>,
431 * or one of the elements of <code>envp</code> is <code>null</code>
432 *
433 * @throws IllegalArgumentException
434 * If <code>command</code> is empty
435 *
436 * @see ProcessBuilder
437 * @since 1.3
438 */
439 public Process exec(String command, String[] envp, File dir)
440 throws IOException {
441 if (command.length() == 0)
442 throw new IllegalArgumentException("Empty command");
443
444 StringTokenizer st = new StringTokenizer(command);
445 String[] cmdarray = new String[st.countTokens()];
446 for (int i = 0; st.hasMoreTokens(); i++)
447 cmdarray[i] = st.nextToken();
448 return exec(cmdarray, envp, dir);
449 }
450
451 /**
452 * Executes the specified command and arguments in a separate process.
453 *
454 * <p>This is a convenience method. An invocation of the form
455 * <tt>exec(cmdarray)</tt>
456 * behaves in exactly the same way as the invocation
457 * <tt>{@link #exec(String[], String[], File) exec}(cmdarray, null, null)</tt>.
458 *
459 * @param cmdarray array containing the command to call and
460 * its arguments.
461 *
462 * @return A new {@link Process} object for managing the subprocess
463 *
464 * @throws SecurityException
465 * If a security manager exists and its
466 * {@link SecurityManager#checkExec checkExec}
467 * method doesn't allow creation of the subprocess
468 *
469 * @throws IOException
470 * If an I/O error occurs
471 *
472 * @throws NullPointerException
473 * If <code>cmdarray</code> is <code>null</code>,
474 * or one of the elements of <code>cmdarray</code> is <code>null</code>
475 *
476 * @throws IndexOutOfBoundsException
477 * If <code>cmdarray</code> is an empty array
478 * (has length <code>0</code>)
479 *
480 * @see ProcessBuilder
481 */
482 public Process exec(String cmdarray[]) throws IOException {
483 return exec(cmdarray, null, null);
484 }
485
486 /**
487 * Executes the specified command and arguments in a separate process
488 * with the specified environment.
489 *
490 * <p>This is a convenience method. An invocation of the form
491 * <tt>exec(cmdarray, envp)</tt>
492 * behaves in exactly the same way as the invocation
493 * <tt>{@link #exec(String[], String[], File) exec}(cmdarray, envp, null)</tt>.
494 *
495 * @param cmdarray array containing the command to call and
496 * its arguments.
497 *
498 * @param envp array of strings, each element of which
499 * has environment variable settings in the format
500 * <i>name</i>=<i>value</i>, or
501 * <tt>null</tt> if the subprocess should inherit
502 * the environment of the current process.
503 *
504 * @return A new {@link Process} object for managing the subprocess
505 *
506 * @throws SecurityException
507 * If a security manager exists and its
508 * {@link SecurityManager#checkExec checkExec}
509 * method doesn't allow creation of the subprocess
510 *
511 * @throws IOException
512 * If an I/O error occurs
513 *
514 * @throws NullPointerException
515 * If <code>cmdarray</code> is <code>null</code>,
516 * or one of the elements of <code>cmdarray</code> is <code>null</code>,
517 * or one of the elements of <code>envp</code> is <code>null</code>
518 *
519 * @throws IndexOutOfBoundsException
520 * If <code>cmdarray</code> is an empty array
521 * (has length <code>0</code>)
522 *
523 * @see ProcessBuilder
524 */
525 public Process exec(String[] cmdarray, String[] envp) throws IOException {
526 return exec(cmdarray, envp, null);
527 }
528
529
530 /**
531 * Executes the specified command and arguments in a separate process with
532 * the specified environment and working directory.
533 *
534 * <p>Given an array of strings <code>cmdarray</code>, representing the
535 * tokens of a command line, and an array of strings <code>envp</code>,
536 * representing "environment" variable settings, this method creates
537 * a new process in which to execute the specified command.
538 *
539 * <p>This method checks that <code>cmdarray</code> is a valid operating
540 * system command. Which commands are valid is system-dependent,
541 * but at the very least the command must be a non-empty list of
542 * non-null strings.
543 *
544 * <p>If <tt>envp</tt> is <tt>null</tt>, the subprocess inherits the
545 * environment settings of the current process.
546 *
547 * <p>A minimal set of system dependent environment variables may
548 * be required to start a process on some operating systems.
549 * As a result, the subprocess may inherit additional environment variable
550 * settings beyond those in the specified environment.
551 *
552 * <p>{@link ProcessBuilder#start()} is now the preferred way to
553 * start a process with a modified environment.
554 *
555 * <p>The working directory of the new subprocess is specified by <tt>dir</tt>.
556 * If <tt>dir</tt> is <tt>null</tt>, the subprocess inherits the
557 * current working directory of the current process.
558 *
559 * <p>If a security manager exists, its
560 * {@link SecurityManager#checkExec checkExec}
561 * method is invoked with the first component of the array
562 * <code>cmdarray</code> as its argument. This may result in a
563 * {@link SecurityException} being thrown.
564 *
565 * <p>Starting an operating system process is highly system-dependent.
566 * Among the many things that can go wrong are:
567 * <ul>
568 * <li>The operating system program file was not found.
569 * <li>Access to the program file was denied.
570 * <li>The working directory does not exist.
571 * </ul>
572 *
573 * <p>In such cases an exception will be thrown. The exact nature
574 * of the exception is system-dependent, but it will always be a
575 * subclass of {@link IOException}.
576 *
577 *
578 * @param cmdarray array containing the command to call and
579 * its arguments.
580 *
581 * @param envp array of strings, each element of which
582 * has environment variable settings in the format
583 * <i>name</i>=<i>value</i>, or
584 * <tt>null</tt> if the subprocess should inherit
585 * the environment of the current process.
586 *
587 * @param dir the working directory of the subprocess, or
588 * <tt>null</tt> if the subprocess should inherit
589 * the working directory of the current process.
590 *
591 * @return A new {@link Process} object for managing the subprocess
592 *
593 * @throws SecurityException
594 * If a security manager exists and its
595 * {@link SecurityManager#checkExec checkExec}
596 * method doesn't allow creation of the subprocess
597 *
598 * @throws IOException
599 * If an I/O error occurs
600 *
601 * @throws NullPointerException
602 * If <code>cmdarray</code> is <code>null</code>,
603 * or one of the elements of <code>cmdarray</code> is <code>null</code>,
604 * or one of the elements of <code>envp</code> is <code>null</code>
605 *
606 * @throws IndexOutOfBoundsException
607 * If <code>cmdarray</code> is an empty array
608 * (has length <code>0</code>)
609 *
610 * @see ProcessBuilder
611 * @since 1.3
612 */
613 public Process exec(String[] cmdarray, String[] envp, File dir)
614 throws IOException {
615 return new ProcessBuilder(cmdarray)
616 .environment(envp)
617 .directory(dir)
618 .start();
619 }
620
621 /**
622 * Returns the number of processors available to the Java virtual machine.
623 *
624 * <p> This value may change during a particular invocation of the virtual
625 * machine. Applications that are sensitive to the number of available
626 * processors should therefore occasionally poll this property and adjust
627 * their resource usage appropriately. </p>
628 *
629 * @return the maximum number of processors available to the virtual
630 * machine; never smaller than one
631 * @since 1.4
632 */
633 public native int availableProcessors();
634
635 /**
636 * Returns the amount of free memory in the Java Virtual Machine.
637 * Calling the
638 * <code>gc</code> method may result in increasing the value returned
639 * by <code>freeMemory.</code>
640 *
641 * @return an approximation to the total amount of memory currently
642 * available for future allocated objects, measured in bytes.
643 */
644 public native long freeMemory();
645
646 /**
647 * Returns the total amount of memory in the Java virtual machine.
648 * The value returned by this method may vary over time, depending on
649 * the host environment.
650 * <p>
651 * Note that the amount of memory required to hold an object of any
652 * given type may be implementation-dependent.
653 *
654 * @return the total amount of memory currently available for current
655 * and future objects, measured in bytes.
656 */
657 public native long totalMemory();
658
659 /**
660 * Returns the maximum amount of memory that the Java virtual machine will
661 * attempt to use. If there is no inherent limit then the value {@link
662 * java.lang.Long#MAX_VALUE} will be returned. </p>
663 *
664 * @return the maximum amount of memory that the virtual machine will
665 * attempt to use, measured in bytes
666 * @since 1.4
667 */
668 public native long maxMemory();
669
670 /**
671 * Runs the garbage collector.
672 * Calling this method suggests that the Java virtual machine expend
673 * effort toward recycling unused objects in order to make the memory
674 * they currently occupy available for quick reuse. When control
675 * returns from the method call, the virtual machine has made
676 * its best effort to recycle all discarded objects.
677 * <p>
678 * The name <code>gc</code> stands for "garbage
679 * collector". The virtual machine performs this recycling
680 * process automatically as needed, in a separate thread, even if the
681 * <code>gc</code> method is not invoked explicitly.
682 * <p>
683 * The method {@link System#gc()} is the conventional and convenient
684 * means of invoking this method.
685 */
686 public native void gc();
687
688 /* Wormhole for calling java.lang.ref.Finalizer.runFinalization */
689 private static native void runFinalization0();
690
691 /**
692 * Runs the finalization methods of any objects pending finalization.
693 * Calling this method suggests that the Java virtual machine expend
694 * effort toward running the <code>finalize</code> methods of objects
695 * that have been found to be discarded but whose <code>finalize</code>
696 * methods have not yet been run. When control returns from the
697 * method call, the virtual machine has made a best effort to
698 * complete all outstanding finalizations.
699 * <p>
700 * The virtual machine performs the finalization process
701 * automatically as needed, in a separate thread, if the
702 * <code>runFinalization</code> method is not invoked explicitly.
703 * <p>
704 * The method {@link System#runFinalization()} is the conventional
705 * and convenient means of invoking this method.
706 *
707 * @see java.lang.Object#finalize()
708 */
709 public void runFinalization() {
710 runFinalization0();
711 }
712
713 /**
714 * Enables/Disables tracing of instructions.
715 * If the <code>boolean</code> argument is <code>true</code>, this
716 * method suggests that the Java virtual machine emit debugging
717 * information for each instruction in the virtual machine as it
718 * is executed. The format of this information, and the file or other
719 * output stream to which it is emitted, depends on the host environment.
720 * The virtual machine may ignore this request if it does not support
721 * this feature. The destination of the trace output is system
722 * dependent.
723 * <p>
724 * If the <code>boolean</code> argument is <code>false</code>, this
725 * method causes the virtual machine to stop performing the
726 * detailed instruction trace it is performing.
727 *
728 * @param on <code>true</code> to enable instruction tracing;
729 * <code>false</code> to disable this feature.
730 */
731 public native void traceInstructions(boolean on);
732
733 /**
734 * Enables/Disables tracing of method calls.
735 * If the <code>boolean</code> argument is <code>true</code>, this
736 * method suggests that the Java virtual machine emit debugging
737 * information for each method in the virtual machine as it is
738 * called. The format of this information, and the file or other output
739 * stream to which it is emitted, depends on the host environment. The
740 * virtual machine may ignore this request if it does not support
741 * this feature.
742 * <p>
743 * Calling this method with argument false suggests that the
744 * virtual machine cease emitting per-call debugging information.
745 *
746 * @param on <code>true</code> to enable instruction tracing;
747 * <code>false</code> to disable this feature.
748 */
749 public native void traceMethodCalls(boolean on);
750
751 /**
752 * Loads the specified filename as a dynamic library. The filename
753 * argument must be a complete path name,
754 * (for example
755 * <code>Runtime.getRuntime().load("/home/avh/lib/libX11.so");</code>).
756 * <p>
757 * First, if there is a security manager, its <code>checkLink</code>
758 * method is called with the <code>filename</code> as its argument.
759 * This may result in a security exception.
760 * <p>
761 * This is similar to the method {@link #loadLibrary(String)}, but it
762 * accepts a general file name as an argument rather than just a library
763 * name, allowing any file of native code to be loaded.
764 * <p>
765 * The method {@link System#load(String)} is the conventional and
766 * convenient means of invoking this method.
767 *
768 * @param filename the file to load.
769 * @exception SecurityException if a security manager exists and its
770 * <code>checkLink</code> method doesn't allow
771 * loading of the specified dynamic library
772 * @exception UnsatisfiedLinkError if the file does not exist.
773 * @exception NullPointerException if <code>filename</code> is
774 * <code>null</code>
775 * @see java.lang.Runtime#getRuntime()
776 * @see java.lang.SecurityException
777 * @see java.lang.SecurityManager#checkLink(java.lang.String)
778 */
779 public void load(String filename) {
780 load0(System.getCallerClass(), filename);
781 }
782
783 synchronized void load0(Class fromClass, String filename) {
784 SecurityManager security = System.getSecurityManager();
785 if (security != null) {
786 security.checkLink(filename);
787 }
788 if (!(new File(filename).isAbsolute())) {
789 throw new UnsatisfiedLinkError(
790 "Expecting an absolute path of the library: " + filename);
791 }
792 ClassLoader.loadLibrary(fromClass, filename, true);
793 }
794
795 /**
796 * Loads the dynamic library with the specified library name.
797 * A file containing native code is loaded from the local file system
798 * from a place where library files are conventionally obtained. The
799 * details of this process are implementation-dependent. The
800 * mapping from a library name to a specific filename is done in a
801 * system-specific manner.
802 * <p>
803 * First, if there is a security manager, its <code>checkLink</code>
804 * method is called with the <code>libname</code> as its argument.
805 * This may result in a security exception.
806 * <p>
807 * The method {@link System#loadLibrary(String)} is the conventional
808 * and convenient means of invoking this method. If native
809 * methods are to be used in the implementation of a class, a standard
810 * strategy is to put the native code in a library file (call it
811 * <code>LibFile</code>) and then to put a static initializer:
812 * <blockquote><pre>
813 * static { System.loadLibrary("LibFile"); }
814 * </pre></blockquote>
815 * within the class declaration. When the class is loaded and
816 * initialized, the necessary native code implementation for the native
817 * methods will then be loaded as well.
818 * <p>
819 * If this method is called more than once with the same library
820 * name, the second and subsequent calls are ignored.
821 *
822 * @param libname the name of the library.
823 * @exception SecurityException if a security manager exists and its
824 * <code>checkLink</code> method doesn't allow
825 * loading of the specified dynamic library
826 * @exception UnsatisfiedLinkError if the library does not exist.
827 * @exception NullPointerException if <code>libname</code> is
828 * <code>null</code>
829 * @see java.lang.SecurityException
830 * @see java.lang.SecurityManager#checkLink(java.lang.String)
831 */
832 public void loadLibrary(String libname) {
833 loadLibrary0(System.getCallerClass(), libname);
834 }
835
836 synchronized void loadLibrary0(Class fromClass, String libname) {
837 SecurityManager security = System.getSecurityManager();
838 if (security != null) {
839 security.checkLink(libname);
840 }
841 if (libname.indexOf((int)File.separatorChar) != -1) {
842 throw new UnsatisfiedLinkError(
843 "Directory separator should not appear in library name: " + libname);
844 }
845 ClassLoader.loadLibrary(fromClass, libname, false);
846 }
847
848 /**
849 * Creates a localized version of an input stream. This method takes
850 * an <code>InputStream</code> and returns an <code>InputStream</code>
851 * equivalent to the argument in all respects except that it is
852 * localized: as characters in the local character set are read from
853 * the stream, they are automatically converted from the local
854 * character set to Unicode.
855 * <p>
856 * If the argument is already a localized stream, it may be returned
857 * as the result.
858 *
859 * @param in InputStream to localize
860 * @return a localized input stream
861 * @see java.io.InputStream
862 * @see java.io.BufferedReader#BufferedReader(java.io.Reader)
863 * @see java.io.InputStreamReader#InputStreamReader(java.io.InputStream)
864 * @deprecated As of JDK 1.1, the preferred way to translate a byte
865 * stream in the local encoding into a character stream in Unicode is via
866 * the <code>InputStreamReader</code> and <code>BufferedReader</code>
867 * classes.
868 */
869 @Deprecated
870 public InputStream getLocalizedInputStream(InputStream in) {
871 return in;
872 }
873
874 /**
875 * Creates a localized version of an output stream. This method
876 * takes an <code>OutputStream</code> and returns an
877 * <code>OutputStream</code> equivalent to the argument in all respects
878 * except that it is localized: as Unicode characters are written to
879 * the stream, they are automatically converted to the local
880 * character set.
881 * <p>
882 * If the argument is already a localized stream, it may be returned
883 * as the result.
884 *
885 * @deprecated As of JDK 1.1, the preferred way to translate a
886 * Unicode character stream into a byte stream in the local encoding is via
887 * the <code>OutputStreamWriter</code>, <code>BufferedWriter</code>, and
888 * <code>PrintWriter</code> classes.
889 *
890 * @param out OutputStream to localize
891 * @return a localized output stream
892 * @see java.io.OutputStream
893 * @see java.io.BufferedWriter#BufferedWriter(java.io.Writer)
894 * @see java.io.OutputStreamWriter#OutputStreamWriter(java.io.OutputStream)
895 * @see java.io.PrintWriter#PrintWriter(java.io.OutputStream)
896 */
897 @Deprecated
898 public OutputStream getLocalizedOutputStream(OutputStream out) {
899 return out;
900 }
901
902 }
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