1 /*
2 * Copyright (c) 1994, 2014, 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.*;
28 import java.lang.reflect.Executable;
29 import java.lang.annotation.Annotation;
30 import java.security.AccessControlContext;
31 import java.util.Properties;
32 import java.util.PropertyPermission;
33 import java.util.StringTokenizer;
34 import java.util.Map;
35 import java.security.AccessController;
36 import java.security.PrivilegedAction;
37 import java.security.AllPermission;
38 import java.nio.channels.Channel;
39 import java.nio.channels.spi.SelectorProvider;
40 import sun.nio.ch.Interruptible;
41 import sun.reflect.CallerSensitive;
42 import sun.reflect.Reflection;
43 import sun.security.util.SecurityConstants;
44 import sun.reflect.annotation.AnnotationType;
45 import jdk.internal.HotSpotIntrinsicCandidate;
46
47 /**
48 * The <code>System</code> class contains several useful class fields
49 * and methods. It cannot be instantiated.
50 *
51 * <p>Among the facilities provided by the <code>System</code> class
52 * are standard input, standard output, and error output streams;
53 * access to externally defined properties and environment
54 * variables; a means of loading files and libraries; and a utility
55 * method for quickly copying a portion of an array.
56 *
57 * @author unascribed
58 * @since 1.0
59 */
60 public final class System {
61
62 /* register the natives via the static initializer.
63 *
64 * VM will invoke the initializeSystemClass method to complete
65 * the initialization for this class separated from clinit.
66 * Note that to use properties set by the VM, see the constraints
67 * described in the initializeSystemClass method.
68 */
69 private static native void registerNatives();
70 static {
71 registerNatives();
72 }
73
74 /** Don't let anyone instantiate this class */
75 private System() {
76 }
77
78 /**
79 * The "standard" input stream. This stream is already
80 * open and ready to supply input data. Typically this stream
81 * corresponds to keyboard input or another input source specified by
82 * the host environment or user.
83 */
84 public final static InputStream in = null;
85
86 /**
87 * The "standard" output stream. This stream is already
88 * open and ready to accept output data. Typically this stream
89 * corresponds to display output or another output destination
90 * specified by the host environment or user.
91 * <p>
92 * For simple stand-alone Java applications, a typical way to write
93 * a line of output data is:
94 * <blockquote><pre>
95 * System.out.println(data)
96 * </pre></blockquote>
97 * <p>
98 * See the <code>println</code> methods in class <code>PrintStream</code>.
99 *
100 * @see java.io.PrintStream#println()
101 * @see java.io.PrintStream#println(boolean)
102 * @see java.io.PrintStream#println(char)
103 * @see java.io.PrintStream#println(char[])
104 * @see java.io.PrintStream#println(double)
105 * @see java.io.PrintStream#println(float)
106 * @see java.io.PrintStream#println(int)
107 * @see java.io.PrintStream#println(long)
108 * @see java.io.PrintStream#println(java.lang.Object)
109 * @see java.io.PrintStream#println(java.lang.String)
110 */
111 public final static PrintStream out = null;
112
113 /**
114 * The "standard" error output stream. This stream is already
115 * open and ready to accept output data.
116 * <p>
117 * Typically this stream corresponds to display output or another
118 * output destination specified by the host environment or user. By
119 * convention, this output stream is used to display error messages
120 * or other information that should come to the immediate attention
121 * of a user even if the principal output stream, the value of the
122 * variable <code>out</code>, has been redirected to a file or other
123 * destination that is typically not continuously monitored.
124 */
125 public final static PrintStream err = null;
126
127 /* The security manager for the system.
128 */
129 private static volatile SecurityManager security = null;
130
131 /**
132 * Reassigns the "standard" input stream.
133 *
134 * <p>First, if there is a security manager, its <code>checkPermission</code>
135 * method is called with a <code>RuntimePermission("setIO")</code> permission
136 * to see if it's ok to reassign the "standard" input stream.
137 *
138 * @param in the new standard input stream.
139 *
140 * @throws SecurityException
141 * if a security manager exists and its
142 * <code>checkPermission</code> method doesn't allow
143 * reassigning of the standard input stream.
144 *
145 * @see SecurityManager#checkPermission
146 * @see java.lang.RuntimePermission
147 *
148 * @since 1.1
149 */
150 public static void setIn(InputStream in) {
151 checkIO();
152 setIn0(in);
153 }
154
155 /**
156 * Reassigns the "standard" output stream.
157 *
158 * <p>First, if there is a security manager, its <code>checkPermission</code>
159 * method is called with a <code>RuntimePermission("setIO")</code> permission
160 * to see if it's ok to reassign the "standard" output stream.
161 *
162 * @param out the new standard output stream
163 *
164 * @throws SecurityException
165 * if a security manager exists and its
166 * <code>checkPermission</code> method doesn't allow
167 * reassigning of the standard output stream.
168 *
169 * @see SecurityManager#checkPermission
170 * @see java.lang.RuntimePermission
171 *
172 * @since 1.1
173 */
174 public static void setOut(PrintStream out) {
175 checkIO();
176 setOut0(out);
177 }
178
179 /**
180 * Reassigns the "standard" error output stream.
181 *
182 * <p>First, if there is a security manager, its <code>checkPermission</code>
183 * method is called with a <code>RuntimePermission("setIO")</code> permission
184 * to see if it's ok to reassign the "standard" error output stream.
185 *
186 * @param err the new standard error output stream.
187 *
188 * @throws SecurityException
189 * if a security manager exists and its
190 * <code>checkPermission</code> method doesn't allow
191 * reassigning of the standard error output stream.
192 *
193 * @see SecurityManager#checkPermission
194 * @see java.lang.RuntimePermission
195 *
196 * @since 1.1
197 */
198 public static void setErr(PrintStream err) {
199 checkIO();
200 setErr0(err);
201 }
202
203 private static volatile Console cons = null;
204 /**
205 * Returns the unique {@link java.io.Console Console} object associated
206 * with the current Java virtual machine, if any.
207 *
208 * @return The system console, if any, otherwise <tt>null</tt>.
209 *
210 * @since 1.6
211 */
212 public static Console console() {
213 if (cons == null) {
214 synchronized (System.class) {
215 cons = sun.misc.SharedSecrets.getJavaIOAccess().console();
216 }
217 }
218 return cons;
219 }
220
221 /**
222 * Returns the channel inherited from the entity that created this
223 * Java virtual machine.
224 *
225 * <p> This method returns the channel obtained by invoking the
226 * {@link java.nio.channels.spi.SelectorProvider#inheritedChannel
227 * inheritedChannel} method of the system-wide default
228 * {@link java.nio.channels.spi.SelectorProvider} object. </p>
229 *
230 * <p> In addition to the network-oriented channels described in
231 * {@link java.nio.channels.spi.SelectorProvider#inheritedChannel
232 * inheritedChannel}, this method may return other kinds of
233 * channels in the future.
234 *
235 * @return The inherited channel, if any, otherwise <tt>null</tt>.
236 *
237 * @throws IOException
238 * If an I/O error occurs
239 *
240 * @throws SecurityException
241 * If a security manager is present and it does not
242 * permit access to the channel.
243 *
244 * @since 1.5
245 */
246 public static Channel inheritedChannel() throws IOException {
247 return SelectorProvider.provider().inheritedChannel();
248 }
249
250 private static void checkIO() {
251 SecurityManager sm = getSecurityManager();
252 if (sm != null) {
253 sm.checkPermission(new RuntimePermission("setIO"));
254 }
255 }
256
257 private static native void setIn0(InputStream in);
258 private static native void setOut0(PrintStream out);
259 private static native void setErr0(PrintStream err);
260
261 /**
262 * Sets the System security.
263 *
264 * <p> If there is a security manager already installed, this method first
265 * calls the security manager's <code>checkPermission</code> method
266 * with a <code>RuntimePermission("setSecurityManager")</code>
267 * permission to ensure it's ok to replace the existing
268 * security manager.
269 * This may result in throwing a <code>SecurityException</code>.
270 *
271 * <p> Otherwise, the argument is established as the current
272 * security manager. If the argument is <code>null</code> and no
273 * security manager has been established, then no action is taken and
274 * the method simply returns.
275 *
276 * @param s the security manager.
277 * @exception SecurityException if the security manager has already
278 * been set and its <code>checkPermission</code> method
279 * doesn't allow it to be replaced.
280 * @see #getSecurityManager
281 * @see SecurityManager#checkPermission
282 * @see java.lang.RuntimePermission
283 */
284 public static
285 void setSecurityManager(final SecurityManager s) {
286 try {
287 s.checkPackageAccess("java.lang");
288 } catch (Exception e) {
289 // no-op
290 }
291 setSecurityManager0(s);
292 }
293
294 private static synchronized
295 void setSecurityManager0(final SecurityManager s) {
296 SecurityManager sm = getSecurityManager();
297 if (sm != null) {
298 // ask the currently installed security manager if we
299 // can replace it.
300 sm.checkPermission(new RuntimePermission
301 ("setSecurityManager"));
302 }
303
304 if ((s != null) && (s.getClass().getClassLoader() != null)) {
305 // New security manager class is not on bootstrap classpath.
306 // Cause policy to get initialized before we install the new
307 // security manager, in order to prevent infinite loops when
308 // trying to initialize the policy (which usually involves
309 // accessing some security and/or system properties, which in turn
310 // calls the installed security manager's checkPermission method
311 // which will loop infinitely if there is a non-system class
312 // (in this case: the new security manager class) on the stack).
313 AccessController.doPrivileged(new PrivilegedAction<>() {
314 public Object run() {
315 s.getClass().getProtectionDomain().implies
316 (SecurityConstants.ALL_PERMISSION);
317 return null;
318 }
319 });
320 }
321
322 security = s;
323 }
324
325 /**
326 * Gets the system security interface.
327 *
328 * @return if a security manager has already been established for the
329 * current application, then that security manager is returned;
330 * otherwise, <code>null</code> is returned.
331 * @see #setSecurityManager
332 */
333 public static SecurityManager getSecurityManager() {
334 return security;
335 }
336
337 /**
338 * Returns the current time in milliseconds. Note that
339 * while the unit of time of the return value is a millisecond,
340 * the granularity of the value depends on the underlying
341 * operating system and may be larger. For example, many
342 * operating systems measure time in units of tens of
343 * milliseconds.
344 *
345 * <p> See the description of the class <code>Date</code> for
346 * a discussion of slight discrepancies that may arise between
347 * "computer time" and coordinated universal time (UTC).
348 *
349 * @return the difference, measured in milliseconds, between
350 * the current time and midnight, January 1, 1970 UTC.
351 * @see java.util.Date
352 */
353 @HotSpotIntrinsicCandidate
354 public static native long currentTimeMillis();
355
356 /**
357 * Returns the current value of the running Java Virtual Machine's
358 * high-resolution time source, in nanoseconds.
359 *
360 * <p>This method can only be used to measure elapsed time and is
361 * not related to any other notion of system or wall-clock time.
362 * The value returned represents nanoseconds since some fixed but
363 * arbitrary <i>origin</i> time (perhaps in the future, so values
364 * may be negative). The same origin is used by all invocations of
365 * this method in an instance of a Java virtual machine; other
366 * virtual machine instances are likely to use a different origin.
367 *
368 * <p>This method provides nanosecond precision, but not necessarily
369 * nanosecond resolution (that is, how frequently the value changes)
370 * - no guarantees are made except that the resolution is at least as
371 * good as that of {@link #currentTimeMillis()}.
372 *
373 * <p>Differences in successive calls that span greater than
374 * approximately 292 years (2<sup>63</sup> nanoseconds) will not
375 * correctly compute elapsed time due to numerical overflow.
376 *
377 * <p>The values returned by this method become meaningful only when
378 * the difference between two such values, obtained within the same
379 * instance of a Java virtual machine, is computed.
380 *
381 * <p>For example, to measure how long some code takes to execute:
382 * <pre> {@code
383 * long startTime = System.nanoTime();
384 * // ... the code being measured ...
385 * long elapsedNanos = System.nanoTime() - startTime;}</pre>
386 *
387 * <p>To compare elapsed time against a timeout, use <pre> {@code
388 * if (System.nanoTime() - startTime >= timeoutNanos) ...}</pre>
389 * instead of <pre> {@code
390 * if (System.nanoTime() >= startTime + timeoutNanos) ...}</pre>
391 * because of the possibility of numerical overflow.
392 *
393 * @return the current value of the running Java Virtual Machine's
394 * high-resolution time source, in nanoseconds
395 * @since 1.5
396 */
397 @HotSpotIntrinsicCandidate
398 public static native long nanoTime();
399
400 /**
401 * Copies an array from the specified source array, beginning at the
402 * specified position, to the specified position of the destination array.
403 * A subsequence of array components are copied from the source
404 * array referenced by <code>src</code> to the destination array
405 * referenced by <code>dest</code>. The number of components copied is
406 * equal to the <code>length</code> argument. The components at
407 * positions <code>srcPos</code> through
408 * <code>srcPos+length-1</code> in the source array are copied into
409 * positions <code>destPos</code> through
410 * <code>destPos+length-1</code>, respectively, of the destination
411 * array.
412 * <p>
413 * If the <code>src</code> and <code>dest</code> arguments refer to the
414 * same array object, then the copying is performed as if the
415 * components at positions <code>srcPos</code> through
416 * <code>srcPos+length-1</code> were first copied to a temporary
417 * array with <code>length</code> components and then the contents of
418 * the temporary array were copied into positions
419 * <code>destPos</code> through <code>destPos+length-1</code> of the
420 * destination array.
421 * <p>
422 * If <code>dest</code> is <code>null</code>, then a
423 * <code>NullPointerException</code> is thrown.
424 * <p>
425 * If <code>src</code> is <code>null</code>, then a
426 * <code>NullPointerException</code> is thrown and the destination
427 * array is not modified.
428 * <p>
429 * Otherwise, if any of the following is true, an
430 * <code>ArrayStoreException</code> is thrown and the destination is
431 * not modified:
432 * <ul>
433 * <li>The <code>src</code> argument refers to an object that is not an
434 * array.
435 * <li>The <code>dest</code> argument refers to an object that is not an
436 * array.
437 * <li>The <code>src</code> argument and <code>dest</code> argument refer
438 * to arrays whose component types are different primitive types.
439 * <li>The <code>src</code> argument refers to an array with a primitive
440 * component type and the <code>dest</code> argument refers to an array
441 * with a reference component type.
442 * <li>The <code>src</code> argument refers to an array with a reference
443 * component type and the <code>dest</code> argument refers to an array
444 * with a primitive component type.
445 * </ul>
446 * <p>
447 * Otherwise, if any of the following is true, an
448 * <code>IndexOutOfBoundsException</code> is
449 * thrown and the destination is not modified:
450 * <ul>
451 * <li>The <code>srcPos</code> argument is negative.
452 * <li>The <code>destPos</code> argument is negative.
453 * <li>The <code>length</code> argument is negative.
454 * <li><code>srcPos+length</code> is greater than
455 * <code>src.length</code>, the length of the source array.
456 * <li><code>destPos+length</code> is greater than
457 * <code>dest.length</code>, the length of the destination array.
458 * </ul>
459 * <p>
460 * Otherwise, if any actual component of the source array from
461 * position <code>srcPos</code> through
462 * <code>srcPos+length-1</code> cannot be converted to the component
463 * type of the destination array by assignment conversion, an
464 * <code>ArrayStoreException</code> is thrown. In this case, let
465 * <b><i>k</i></b> be the smallest nonnegative integer less than
466 * length such that <code>src[srcPos+</code><i>k</i><code>]</code>
467 * cannot be converted to the component type of the destination
468 * array; when the exception is thrown, source array components from
469 * positions <code>srcPos</code> through
470 * <code>srcPos+</code><i>k</i><code>-1</code>
471 * will already have been copied to destination array positions
472 * <code>destPos</code> through
473 * <code>destPos+</code><i>k</I><code>-1</code> and no other
474 * positions of the destination array will have been modified.
475 * (Because of the restrictions already itemized, this
476 * paragraph effectively applies only to the situation where both
477 * arrays have component types that are reference types.)
478 *
479 * @param src the source array.
480 * @param srcPos starting position in the source array.
481 * @param dest the destination array.
482 * @param destPos starting position in the destination data.
483 * @param length the number of array elements to be copied.
484 * @exception IndexOutOfBoundsException if copying would cause
485 * access of data outside array bounds.
486 * @exception ArrayStoreException if an element in the <code>src</code>
487 * array could not be stored into the <code>dest</code> array
488 * because of a type mismatch.
489 * @exception NullPointerException if either <code>src</code> or
490 * <code>dest</code> is <code>null</code>.
491 */
492 @HotSpotIntrinsicCandidate
493 public static native void arraycopy(Object src, int srcPos,
494 Object dest, int destPos,
495 int length);
496
497 /**
498 * Returns the same hash code for the given object as
499 * would be returned by the default method hashCode(),
500 * whether or not the given object's class overrides
501 * hashCode().
502 * The hash code for the null reference is zero.
503 *
504 * @param x object for which the hashCode is to be calculated
505 * @return the hashCode
506 * @since 1.1
507 */
508 @HotSpotIntrinsicCandidate
509 public static native int identityHashCode(Object x);
510
511 /**
512 * System properties. The following properties are guaranteed to be defined:
513 * <dl>
514 * <dt>java.version <dd>Java version number
515 * <dt>java.vendor <dd>Java vendor specific string
516 * <dt>java.vendor.url <dd>Java vendor URL
517 * <dt>java.home <dd>Java installation directory
518 * <dt>java.class.version <dd>Java class version number
519 * <dt>java.class.path <dd>Java classpath
520 * <dt>os.name <dd>Operating System Name
521 * <dt>os.arch <dd>Operating System Architecture
522 * <dt>os.version <dd>Operating System Version
523 * <dt>file.separator <dd>File separator ("/" on Unix)
524 * <dt>path.separator <dd>Path separator (":" on Unix)
525 * <dt>line.separator <dd>Line separator ("\n" on Unix)
526 * <dt>user.name <dd>User account name
527 * <dt>user.home <dd>User home directory
528 * <dt>user.dir <dd>User's current working directory
529 * </dl>
530 */
531
532 private static Properties props;
533 private static native Properties initProperties(Properties props);
534
535 /**
536 * Determines the current system properties.
537 * <p>
538 * First, if there is a security manager, its
539 * <code>checkPropertiesAccess</code> method is called with no
540 * arguments. This may result in a security exception.
541 * <p>
542 * The current set of system properties for use by the
543 * {@link #getProperty(String)} method is returned as a
544 * <code>Properties</code> object. If there is no current set of
545 * system properties, a set of system properties is first created and
546 * initialized. This set of system properties always includes values
547 * for the following keys:
548 * <table summary="Shows property keys and associated values">
549 * <tr><th>Key</th>
550 * <th>Description of Associated Value</th></tr>
551 * <tr><td><code>java.version</code></td>
552 * <td>Java Runtime Environment version</td></tr>
553 * <tr><td><code>java.vendor</code></td>
554 * <td>Java Runtime Environment vendor</td></tr>
555 * <tr><td><code>java.vendor.url</code></td>
556 * <td>Java vendor URL</td></tr>
557 * <tr><td><code>java.home</code></td>
558 * <td>Java installation directory</td></tr>
559 * <tr><td><code>java.vm.specification.version</code></td>
560 * <td>Java Virtual Machine specification version</td></tr>
561 * <tr><td><code>java.vm.specification.vendor</code></td>
562 * <td>Java Virtual Machine specification vendor</td></tr>
563 * <tr><td><code>java.vm.specification.name</code></td>
564 * <td>Java Virtual Machine specification name</td></tr>
565 * <tr><td><code>java.vm.version</code></td>
566 * <td>Java Virtual Machine implementation version</td></tr>
567 * <tr><td><code>java.vm.vendor</code></td>
568 * <td>Java Virtual Machine implementation vendor</td></tr>
569 * <tr><td><code>java.vm.name</code></td>
570 * <td>Java Virtual Machine implementation name</td></tr>
571 * <tr><td><code>java.specification.version</code></td>
572 * <td>Java Runtime Environment specification version</td></tr>
573 * <tr><td><code>java.specification.vendor</code></td>
574 * <td>Java Runtime Environment specification vendor</td></tr>
575 * <tr><td><code>java.specification.name</code></td>
576 * <td>Java Runtime Environment specification name</td></tr>
577 * <tr><td><code>java.class.version</code></td>
578 * <td>Java class format version number</td></tr>
579 * <tr><td><code>java.class.path</code></td>
580 * <td>Java class path</td></tr>
581 * <tr><td><code>java.library.path</code></td>
582 * <td>List of paths to search when loading libraries</td></tr>
583 * <tr><td><code>java.io.tmpdir</code></td>
584 * <td>Default temp file path</td></tr>
585 * <tr><td><code>java.compiler</code></td>
586 * <td>Name of JIT compiler to use</td></tr>
587 * <tr><td><code>os.name</code></td>
588 * <td>Operating system name</td></tr>
589 * <tr><td><code>os.arch</code></td>
590 * <td>Operating system architecture</td></tr>
591 * <tr><td><code>os.version</code></td>
592 * <td>Operating system version</td></tr>
593 * <tr><td><code>file.separator</code></td>
594 * <td>File separator ("/" on UNIX)</td></tr>
595 * <tr><td><code>path.separator</code></td>
596 * <td>Path separator (":" on UNIX)</td></tr>
597 * <tr><td><code>line.separator</code></td>
598 * <td>Line separator ("\n" on UNIX)</td></tr>
599 * <tr><td><code>user.name</code></td>
600 * <td>User's account name</td></tr>
601 * <tr><td><code>user.home</code></td>
602 * <td>User's home directory</td></tr>
603 * <tr><td><code>user.dir</code></td>
604 * <td>User's current working directory</td></tr>
605 * </table>
606 * <p>
607 * Multiple paths in a system property value are separated by the path
608 * separator character of the platform.
609 * <p>
610 * Note that even if the security manager does not permit the
611 * <code>getProperties</code> operation, it may choose to permit the
612 * {@link #getProperty(String)} operation.
613 *
614 * @return the system properties
615 * @exception SecurityException if a security manager exists and its
616 * <code>checkPropertiesAccess</code> method doesn't allow access
617 * to the system properties.
618 * @see #setProperties
619 * @see java.lang.SecurityException
620 * @see java.lang.SecurityManager#checkPropertiesAccess()
621 * @see java.util.Properties
622 */
623 public static Properties getProperties() {
624 SecurityManager sm = getSecurityManager();
625 if (sm != null) {
626 sm.checkPropertiesAccess();
627 }
628
629 return props;
630 }
631
632 /**
633 * Returns the system-dependent line separator string. It always
634 * returns the same value - the initial value of the {@linkplain
635 * #getProperty(String) system property} {@code line.separator}.
636 *
637 * <p>On UNIX systems, it returns {@code "\n"}; on Microsoft
638 * Windows systems it returns {@code "\r\n"}.
639 *
640 * @return the system-dependent line separator string
641 * @since 1.7
642 */
643 public static String lineSeparator() {
644 return lineSeparator;
645 }
646
647 private static String lineSeparator;
648
649 /**
650 * Sets the system properties to the <code>Properties</code>
651 * argument.
652 * <p>
653 * First, if there is a security manager, its
654 * <code>checkPropertiesAccess</code> method is called with no
655 * arguments. This may result in a security exception.
656 * <p>
657 * The argument becomes the current set of system properties for use
658 * by the {@link #getProperty(String)} method. If the argument is
659 * <code>null</code>, then the current set of system properties is
660 * forgotten.
661 *
662 * @param props the new system properties.
663 * @exception SecurityException if a security manager exists and its
664 * <code>checkPropertiesAccess</code> method doesn't allow access
665 * to the system properties.
666 * @see #getProperties
667 * @see java.util.Properties
668 * @see java.lang.SecurityException
669 * @see java.lang.SecurityManager#checkPropertiesAccess()
670 */
671 public static void setProperties(Properties props) {
672 SecurityManager sm = getSecurityManager();
673 if (sm != null) {
674 sm.checkPropertiesAccess();
675 }
676 if (props == null) {
677 props = new Properties();
678 initProperties(props);
679 }
680 System.props = props;
681 }
682
683 /**
684 * Gets the system property indicated by the specified key.
685 * <p>
686 * First, if there is a security manager, its
687 * <code>checkPropertyAccess</code> method is called with the key as
688 * its argument. This may result in a SecurityException.
689 * <p>
690 * If there is no current set of system properties, a set of system
691 * properties is first created and initialized in the same manner as
692 * for the <code>getProperties</code> method.
693 *
694 * @param key the name of the system property.
695 * @return the string value of the system property,
696 * or <code>null</code> if there is no property with that key.
697 *
698 * @exception SecurityException if a security manager exists and its
699 * <code>checkPropertyAccess</code> method doesn't allow
700 * access to the specified system property.
701 * @exception NullPointerException if <code>key</code> is
702 * <code>null</code>.
703 * @exception IllegalArgumentException if <code>key</code> is empty.
704 * @see #setProperty
705 * @see java.lang.SecurityException
706 * @see java.lang.SecurityManager#checkPropertyAccess(java.lang.String)
707 * @see java.lang.System#getProperties()
708 */
709 public static String getProperty(String key) {
710 checkKey(key);
711 SecurityManager sm = getSecurityManager();
712 if (sm != null) {
713 sm.checkPropertyAccess(key);
714 }
715
716 return props.getProperty(key);
717 }
718
719 /**
720 * Gets the system property indicated by the specified key.
721 * <p>
722 * First, if there is a security manager, its
723 * <code>checkPropertyAccess</code> method is called with the
724 * <code>key</code> as its argument.
725 * <p>
726 * If there is no current set of system properties, a set of system
727 * properties is first created and initialized in the same manner as
728 * for the <code>getProperties</code> method.
729 *
730 * @param key the name of the system property.
731 * @param def a default value.
732 * @return the string value of the system property,
733 * or the default value if there is no property with that key.
734 *
735 * @exception SecurityException if a security manager exists and its
736 * <code>checkPropertyAccess</code> method doesn't allow
737 * access to the specified system property.
738 * @exception NullPointerException if <code>key</code> is
739 * <code>null</code>.
740 * @exception IllegalArgumentException if <code>key</code> is empty.
741 * @see #setProperty
742 * @see java.lang.SecurityManager#checkPropertyAccess(java.lang.String)
743 * @see java.lang.System#getProperties()
744 */
745 public static String getProperty(String key, String def) {
746 checkKey(key);
747 SecurityManager sm = getSecurityManager();
748 if (sm != null) {
749 sm.checkPropertyAccess(key);
750 }
751
752 return props.getProperty(key, def);
753 }
754
755 /**
756 * Sets the system property indicated by the specified key.
757 * <p>
758 * First, if a security manager exists, its
759 * <code>SecurityManager.checkPermission</code> method
760 * is called with a <code>PropertyPermission(key, "write")</code>
761 * permission. This may result in a SecurityException being thrown.
762 * If no exception is thrown, the specified property is set to the given
763 * value.
764 *
765 * @param key the name of the system property.
766 * @param value the value of the system property.
767 * @return the previous value of the system property,
768 * or <code>null</code> if it did not have one.
769 *
770 * @exception SecurityException if a security manager exists and its
771 * <code>checkPermission</code> method doesn't allow
772 * setting of the specified property.
773 * @exception NullPointerException if <code>key</code> or
774 * <code>value</code> is <code>null</code>.
775 * @exception IllegalArgumentException if <code>key</code> is empty.
776 * @see #getProperty
777 * @see java.lang.System#getProperty(java.lang.String)
778 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
779 * @see java.util.PropertyPermission
780 * @see SecurityManager#checkPermission
781 * @since 1.2
782 */
783 public static String setProperty(String key, String value) {
784 checkKey(key);
785 SecurityManager sm = getSecurityManager();
786 if (sm != null) {
787 sm.checkPermission(new PropertyPermission(key,
788 SecurityConstants.PROPERTY_WRITE_ACTION));
789 }
790
791 return (String) props.setProperty(key, value);
792 }
793
794 /**
795 * Removes the system property indicated by the specified key.
796 * <p>
797 * First, if a security manager exists, its
798 * <code>SecurityManager.checkPermission</code> method
799 * is called with a <code>PropertyPermission(key, "write")</code>
800 * permission. This may result in a SecurityException being thrown.
801 * If no exception is thrown, the specified property is removed.
802 *
803 * @param key the name of the system property to be removed.
804 * @return the previous string value of the system property,
805 * or <code>null</code> if there was no property with that key.
806 *
807 * @exception SecurityException if a security manager exists and its
808 * <code>checkPropertyAccess</code> method doesn't allow
809 * access to the specified system property.
810 * @exception NullPointerException if <code>key</code> is
811 * <code>null</code>.
812 * @exception IllegalArgumentException if <code>key</code> is empty.
813 * @see #getProperty
814 * @see #setProperty
815 * @see java.util.Properties
816 * @see java.lang.SecurityException
817 * @see java.lang.SecurityManager#checkPropertiesAccess()
818 * @since 1.5
819 */
820 public static String clearProperty(String key) {
821 checkKey(key);
822 SecurityManager sm = getSecurityManager();
823 if (sm != null) {
824 sm.checkPermission(new PropertyPermission(key, "write"));
825 }
826
827 return (String) props.remove(key);
828 }
829
830 private static void checkKey(String key) {
831 if (key == null) {
832 throw new NullPointerException("key can't be null");
833 }
834 if (key.equals("")) {
835 throw new IllegalArgumentException("key can't be empty");
836 }
837 }
838
839 /**
840 * Gets the value of the specified environment variable. An
841 * environment variable is a system-dependent external named
842 * value.
843 *
844 * <p>If a security manager exists, its
845 * {@link SecurityManager#checkPermission checkPermission}
846 * method is called with a
847 * <code>{@link RuntimePermission}("getenv."+name)</code>
848 * permission. This may result in a {@link SecurityException}
849 * being thrown. If no exception is thrown the value of the
850 * variable <code>name</code> is returned.
851 *
852 * <p><a name="EnvironmentVSSystemProperties"><i>System
853 * properties</i> and <i>environment variables</i></a> are both
854 * conceptually mappings between names and values. Both
855 * mechanisms can be used to pass user-defined information to a
856 * Java process. Environment variables have a more global effect,
857 * because they are visible to all descendants of the process
858 * which defines them, not just the immediate Java subprocess.
859 * They can have subtly different semantics, such as case
860 * insensitivity, on different operating systems. For these
861 * reasons, environment variables are more likely to have
862 * unintended side effects. It is best to use system properties
863 * where possible. Environment variables should be used when a
864 * global effect is desired, or when an external system interface
865 * requires an environment variable (such as <code>PATH</code>).
866 *
867 * <p>On UNIX systems the alphabetic case of <code>name</code> is
868 * typically significant, while on Microsoft Windows systems it is
869 * typically not. For example, the expression
870 * <code>System.getenv("FOO").equals(System.getenv("foo"))</code>
871 * is likely to be true on Microsoft Windows.
872 *
873 * @param name the name of the environment variable
874 * @return the string value of the variable, or <code>null</code>
875 * if the variable is not defined in the system environment
876 * @throws NullPointerException if <code>name</code> is <code>null</code>
877 * @throws SecurityException
878 * if a security manager exists and its
879 * {@link SecurityManager#checkPermission checkPermission}
880 * method doesn't allow access to the environment variable
881 * <code>name</code>
882 * @see #getenv()
883 * @see ProcessBuilder#environment()
884 */
885 public static String getenv(String name) {
886 SecurityManager sm = getSecurityManager();
887 if (sm != null) {
888 sm.checkPermission(new RuntimePermission("getenv."+name));
889 }
890
891 return ProcessEnvironment.getenv(name);
892 }
893
894
895 /**
896 * Returns an unmodifiable string map view of the current system environment.
897 * The environment is a system-dependent mapping from names to
898 * values which is passed from parent to child processes.
899 *
900 * <p>If the system does not support environment variables, an
901 * empty map is returned.
902 *
903 * <p>The returned map will never contain null keys or values.
904 * Attempting to query the presence of a null key or value will
905 * throw a {@link NullPointerException}. Attempting to query
906 * the presence of a key or value which is not of type
907 * {@link String} will throw a {@link ClassCastException}.
908 *
909 * <p>The returned map and its collection views may not obey the
910 * general contract of the {@link Object#equals} and
911 * {@link Object#hashCode} methods.
912 *
913 * <p>The returned map is typically case-sensitive on all platforms.
914 *
915 * <p>If a security manager exists, its
916 * {@link SecurityManager#checkPermission checkPermission}
917 * method is called with a
918 * <code>{@link RuntimePermission}("getenv.*")</code>
919 * permission. This may result in a {@link SecurityException} being
920 * thrown.
921 *
922 * <p>When passing information to a Java subprocess,
923 * <a href=#EnvironmentVSSystemProperties>system properties</a>
924 * are generally preferred over environment variables.
925 *
926 * @return the environment as a map of variable names to values
927 * @throws SecurityException
928 * if a security manager exists and its
929 * {@link SecurityManager#checkPermission checkPermission}
930 * method doesn't allow access to the process environment
931 * @see #getenv(String)
932 * @see ProcessBuilder#environment()
933 * @since 1.5
934 */
935 public static java.util.Map<String,String> getenv() {
936 SecurityManager sm = getSecurityManager();
937 if (sm != null) {
938 sm.checkPermission(new RuntimePermission("getenv.*"));
939 }
940
941 return ProcessEnvironment.getenv();
942 }
943
944 /**
945 * Terminates the currently running Java Virtual Machine. The
946 * argument serves as a status code; by convention, a nonzero status
947 * code indicates abnormal termination.
948 * <p>
949 * This method calls the <code>exit</code> method in class
950 * <code>Runtime</code>. This method never returns normally.
951 * <p>
952 * The call <code>System.exit(n)</code> is effectively equivalent to
953 * the call:
954 * <blockquote><pre>
955 * Runtime.getRuntime().exit(n)
956 * </pre></blockquote>
957 *
958 * @param status exit status.
959 * @throws SecurityException
960 * if a security manager exists and its <code>checkExit</code>
961 * method doesn't allow exit with the specified status.
962 * @see java.lang.Runtime#exit(int)
963 */
964 public static void exit(int status) {
965 Runtime.getRuntime().exit(status);
966 }
967
968 /**
969 * Runs the garbage collector.
970 * <p>
971 * Calling the <code>gc</code> method suggests that the Java Virtual
972 * Machine expend effort toward recycling unused objects in order to
973 * make the memory they currently occupy available for quick reuse.
974 * When control returns from the method call, the Java Virtual
975 * Machine has made a best effort to reclaim space from all discarded
976 * objects.
977 * <p>
978 * The call <code>System.gc()</code> is effectively equivalent to the
979 * call:
980 * <blockquote><pre>
981 * Runtime.getRuntime().gc()
982 * </pre></blockquote>
983 *
984 * @see java.lang.Runtime#gc()
985 */
986 public static void gc() {
987 Runtime.getRuntime().gc();
988 }
989
990 /**
991 * Runs the finalization methods of any objects pending finalization.
992 * <p>
993 * Calling this method suggests that the Java Virtual Machine expend
994 * effort toward running the <code>finalize</code> methods of objects
995 * that have been found to be discarded but whose <code>finalize</code>
996 * methods have not yet been run. When control returns from the
997 * method call, the Java Virtual Machine has made a best effort to
998 * complete all outstanding finalizations.
999 * <p>
1000 * The call <code>System.runFinalization()</code> is effectively
1001 * equivalent to the call:
1002 * <blockquote><pre>
1003 * Runtime.getRuntime().runFinalization()
1004 * </pre></blockquote>
1005 *
1006 * @see java.lang.Runtime#runFinalization()
1007 */
1008 public static void runFinalization() {
1009 Runtime.getRuntime().runFinalization();
1010 }
1011
1012 /**
1013 * Enable or disable finalization on exit; doing so specifies that the
1014 * finalizers of all objects that have finalizers that have not yet been
1015 * automatically invoked are to be run before the Java runtime exits.
1016 * By default, finalization on exit is disabled.
1017 *
1018 * <p>If there is a security manager,
1019 * its <code>checkExit</code> method is first called
1020 * with 0 as its argument to ensure the exit is allowed.
1021 * This could result in a SecurityException.
1022 *
1023 * @deprecated This method is inherently unsafe. It may result in
1024 * finalizers being called on live objects while other threads are
1025 * concurrently manipulating those objects, resulting in erratic
1026 * behavior or deadlock.
1027 * @param value indicating enabling or disabling of finalization
1028 * @throws SecurityException
1029 * if a security manager exists and its <code>checkExit</code>
1030 * method doesn't allow the exit.
1031 *
1032 * @see java.lang.Runtime#exit(int)
1033 * @see java.lang.Runtime#gc()
1034 * @see java.lang.SecurityManager#checkExit(int)
1035 * @since 1.1
1036 */
1037 @Deprecated
1038 public static void runFinalizersOnExit(boolean value) {
1039 Runtime.runFinalizersOnExit(value);
1040 }
1041
1042 /**
1043 * Loads the native library specified by the filename argument. The filename
1044 * argument must be an absolute path name.
1045 *
1046 * If the filename argument, when stripped of any platform-specific library
1047 * prefix, path, and file extension, indicates a library whose name is,
1048 * for example, L, and a native library called L is statically linked
1049 * with the VM, then the JNI_OnLoad_L function exported by the library
1050 * is invoked rather than attempting to load a dynamic library.
1051 * A filename matching the argument does not have to exist in the
1052 * file system.
1053 * See the JNI Specification for more details.
1054 *
1055 * Otherwise, the filename argument is mapped to a native library image in
1056 * an implementation-dependent manner.
1057 *
1058 * <p>
1059 * The call <code>System.load(name)</code> is effectively equivalent
1060 * to the call:
1061 * <blockquote><pre>
1062 * Runtime.getRuntime().load(name)
1063 * </pre></blockquote>
1064 *
1065 * @param filename the file to load.
1066 * @exception SecurityException if a security manager exists and its
1067 * <code>checkLink</code> method doesn't allow
1068 * loading of the specified dynamic library
1069 * @exception UnsatisfiedLinkError if either the filename is not an
1070 * absolute path name, the native library is not statically
1071 * linked with the VM, or the library cannot be mapped to
1072 * a native library image by the host system.
1073 * @exception NullPointerException if <code>filename</code> is
1074 * <code>null</code>
1075 * @see java.lang.Runtime#load(java.lang.String)
1076 * @see java.lang.SecurityManager#checkLink(java.lang.String)
1077 */
1078 @CallerSensitive
1079 public static void load(String filename) {
1080 Runtime.getRuntime().load0(Reflection.getCallerClass(), filename);
1081 }
1082
1083 /**
1084 * Loads the native library specified by the <code>libname</code>
1085 * argument. The <code>libname</code> argument must not contain any platform
1086 * specific prefix, file extension or path. If a native library
1087 * called <code>libname</code> is statically linked with the VM, then the
1088 * JNI_OnLoad_<code>libname</code> function exported by the library is invoked.
1089 * See the JNI Specification for more details.
1090 *
1091 * Otherwise, the libname argument is loaded from a system library
1092 * location and mapped to a native library image in an implementation-
1093 * dependent manner.
1094 * <p>
1095 * The call <code>System.loadLibrary(name)</code> is effectively
1096 * equivalent to the call
1097 * <blockquote><pre>
1098 * Runtime.getRuntime().loadLibrary(name)
1099 * </pre></blockquote>
1100 *
1101 * @param libname the name of the library.
1102 * @exception SecurityException if a security manager exists and its
1103 * <code>checkLink</code> method doesn't allow
1104 * loading of the specified dynamic library
1105 * @exception UnsatisfiedLinkError if either the libname argument
1106 * contains a file path, the native library is not statically
1107 * linked with the VM, or the library cannot be mapped to a
1108 * native library image by the host system.
1109 * @exception NullPointerException if <code>libname</code> is
1110 * <code>null</code>
1111 * @see java.lang.Runtime#loadLibrary(java.lang.String)
1112 * @see java.lang.SecurityManager#checkLink(java.lang.String)
1113 */
1114 @CallerSensitive
1115 public static void loadLibrary(String libname) {
1116 Runtime.getRuntime().loadLibrary0(Reflection.getCallerClass(), libname);
1117 }
1118
1119 /**
1120 * Maps a library name into a platform-specific string representing
1121 * a native library.
1122 *
1123 * @param libname the name of the library.
1124 * @return a platform-dependent native library name.
1125 * @exception NullPointerException if <code>libname</code> is
1126 * <code>null</code>
1127 * @see java.lang.System#loadLibrary(java.lang.String)
1128 * @see java.lang.ClassLoader#findLibrary(java.lang.String)
1129 * @since 1.2
1130 */
1131 public static native String mapLibraryName(String libname);
1132
1133 /**
1134 * Create PrintStream for stdout/err based on encoding.
1135 */
1136 private static PrintStream newPrintStream(FileOutputStream fos, String enc) {
1137 if (enc != null) {
1138 try {
1139 return new PrintStream(new BufferedOutputStream(fos, 128), true, enc);
1140 } catch (UnsupportedEncodingException uee) {}
1141 }
1142 return new PrintStream(new BufferedOutputStream(fos, 128), true);
1143 }
1144
1145
1146 /**
1147 * Initialize the system class. Called after thread initialization.
1148 */
1149 private static void initializeSystemClass() {
1150
1151 // VM might invoke JNU_NewStringPlatform() to set those encoding
1152 // sensitive properties (user.home, user.name, boot.class.path, etc.)
1153 // during "props" initialization, in which it may need access, via
1154 // System.getProperty(), to the related system encoding property that
1155 // have been initialized (put into "props") at early stage of the
1156 // initialization. So make sure the "props" is available at the
1157 // very beginning of the initialization and all system properties to
1158 // be put into it directly.
1159 props = new Properties();
1160 initProperties(props); // initialized by the VM
1161
1162 // There are certain system configurations that may be controlled by
1163 // VM options such as the maximum amount of direct memory and
1164 // Integer cache size used to support the object identity semantics
1165 // of autoboxing. Typically, the library will obtain these values
1166 // from the properties set by the VM. If the properties are for
1167 // internal implementation use only, these properties should be
1168 // removed from the system properties.
1169 //
1170 // See java.lang.Integer.IntegerCache and the
1171 // sun.misc.VM.saveAndRemoveProperties method for example.
1172 //
1173 // Save a private copy of the system properties object that
1174 // can only be accessed by the internal implementation. Remove
1175 // certain system properties that are not intended for public access.
1176 sun.misc.VM.saveAndRemoveProperties(props);
1177
1178
1179 lineSeparator = props.getProperty("line.separator");
1180 sun.misc.Version.init();
1181
1182 FileInputStream fdIn = new FileInputStream(FileDescriptor.in);
1183 FileOutputStream fdOut = new FileOutputStream(FileDescriptor.out);
1184 FileOutputStream fdErr = new FileOutputStream(FileDescriptor.err);
1185 setIn0(new BufferedInputStream(fdIn));
1186 setOut0(newPrintStream(fdOut, props.getProperty("sun.stdout.encoding")));
1187 setErr0(newPrintStream(fdErr, props.getProperty("sun.stderr.encoding")));
1188
1189 // Load the zip library now in order to keep java.util.zip.ZipFile
1190 // from trying to use itself to load this library later.
1191 loadLibrary("zip");
1192
1193 // Setup Java signal handlers for HUP, TERM, and INT (where available).
1194 Terminator.setup();
1195
1196 // Initialize any miscellaneous operating system settings that need to be
1197 // set for the class libraries. Currently this is no-op everywhere except
1198 // for Windows where the process-wide error mode is set before the java.io
1199 // classes are used.
1200 sun.misc.VM.initializeOSEnvironment();
1201
1202 // The main thread is not added to its thread group in the same
1203 // way as other threads; we must do it ourselves here.
1204 Thread current = Thread.currentThread();
1205 current.getThreadGroup().add(current);
1206
1207 // register shared secrets
1208 setJavaLangAccess();
1209
1210 // Subsystems that are invoked during initialization can invoke
1211 // sun.misc.VM.isBooted() in order to avoid doing things that should
1212 // wait until the application class loader has been set up.
1213 // IMPORTANT: Ensure that this remains the last initialization action!
1214 sun.misc.VM.booted();
1215 }
1216
1217 private static void setJavaLangAccess() {
1218 // Allow privileged classes outside of java.lang
1219 sun.misc.SharedSecrets.setJavaLangAccess(new sun.misc.JavaLangAccess(){
1220 public sun.reflect.ConstantPool getConstantPool(Class<?> klass) {
1221 return klass.getConstantPool();
1222 }
1223 public boolean casAnnotationType(Class<?> klass, AnnotationType oldType, AnnotationType newType) {
1224 return klass.casAnnotationType(oldType, newType);
1225 }
1226 public AnnotationType getAnnotationType(Class<?> klass) {
1227 return klass.getAnnotationType();
1228 }
1229 public Map<Class<? extends Annotation>, Annotation> getDeclaredAnnotationMap(Class<?> klass) {
1230 return klass.getDeclaredAnnotationMap();
1231 }
1232 public byte[] getRawClassAnnotations(Class<?> klass) {
1233 return klass.getRawAnnotations();
1234 }
1235 public byte[] getRawClassTypeAnnotations(Class<?> klass) {
1236 return klass.getRawTypeAnnotations();
1237 }
1238 public byte[] getRawExecutableTypeAnnotations(Executable executable) {
1239 return Class.getExecutableTypeAnnotationBytes(executable);
1240 }
1241 public <E extends Enum<E>>
1242 E[] getEnumConstantsShared(Class<E> klass) {
1243 return klass.getEnumConstantsShared();
1244 }
1245 public void blockedOn(Thread t, Interruptible b) {
1246 t.blockedOn(b);
1247 }
1248 public void registerShutdownHook(int slot, boolean registerShutdownInProgress, Runnable hook) {
1249 Shutdown.add(slot, registerShutdownInProgress, hook);
1250 }
1251 public int getStackTraceDepth(Throwable t) {
1252 return t.getStackTraceDepth();
1253 }
1254 public StackTraceElement getStackTraceElement(Throwable t, int i) {
1255 return t.getStackTraceElement(i);
1256 }
1257 public String newStringUnsafe(char[] chars) {
1258 return new String(chars, true);
1259 }
1260 public Thread newThreadWithAcc(Runnable target, AccessControlContext acc) {
1261 return new Thread(target, acc);
1262 }
1263 public void invokeFinalize(Object o) throws Throwable {
1264 o.finalize();
1265 }
1266 public void formatUnsignedLong(long val, int shift, char[] buf, int offset, int len) {
1267 Long.formatUnsignedLong(val, shift, buf, offset, len);
1268 }
1269 public void formatUnsignedInt(int val, int shift, char[] buf, int offset, int len) {
1270 Integer.formatUnsignedInt(val, shift, buf, offset, len);
1271 }
1272 });
1273 }
1274 }