1 /*
2 * Copyright (c) 1994, 2011, 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.security.AccessControlContext;
29 import java.util.Properties;
30 import java.util.PropertyPermission;
31 import java.util.StringTokenizer;
32 import java.security.AccessController;
33 import java.security.PrivilegedAction;
34 import java.security.AllPermission;
35 import java.nio.channels.Channel;
36 import java.nio.channels.spi.SelectorProvider;
37 import sun.nio.ch.Interruptible;
38 import sun.reflect.CallerSensitive;
39 import sun.reflect.Reflection;
40 import sun.security.util.SecurityConstants;
41 import sun.reflect.annotation.AnnotationType;
42
43 /**
44 * The <code>System</code> class contains several useful class fields
45 * and methods. It cannot be instantiated.
46 *
47 * <p>Among the facilities provided by the <code>System</code> class
48 * are standard input, standard output, and error output streams;
49 * access to externally defined properties and environment
50 * variables; a means of loading files and libraries; and a utility
51 * method for quickly copying a portion of an array.
52 *
53 * @author unascribed
54 * @since JDK1.0
55 */
56 public final class System {
57
58 /* register the natives via the static initializer.
59 *
60 * VM will invoke the initializeSystemClass method to complete
61 * the initialization for this class separated from clinit.
62 * Note that to use properties set by the VM, see the constraints
63 * described in the initializeSystemClass method.
64 */
65 private static native void registerNatives();
66 static {
67 registerNatives();
68 }
69
70 /** Don't let anyone instantiate this class */
71 private System() {
72 }
73
74 /**
75 * The "standard" input stream. This stream is already
76 * open and ready to supply input data. Typically this stream
77 * corresponds to keyboard input or another input source specified by
78 * the host environment or user.
79 */
80 public final static InputStream in = null;
81
82 /**
83 * The "standard" output stream. This stream is already
84 * open and ready to accept output data. Typically this stream
85 * corresponds to display output or another output destination
86 * specified by the host environment or user.
87 * <p>
88 * For simple stand-alone Java applications, a typical way to write
89 * a line of output data is:
90 * <blockquote><pre>
91 * System.out.println(data)
92 * </pre></blockquote>
93 * <p>
94 * See the <code>println</code> methods in class <code>PrintStream</code>.
95 *
96 * @see java.io.PrintStream#println()
97 * @see java.io.PrintStream#println(boolean)
98 * @see java.io.PrintStream#println(char)
99 * @see java.io.PrintStream#println(char[])
100 * @see java.io.PrintStream#println(double)
101 * @see java.io.PrintStream#println(float)
102 * @see java.io.PrintStream#println(int)
103 * @see java.io.PrintStream#println(long)
104 * @see java.io.PrintStream#println(java.lang.Object)
105 * @see java.io.PrintStream#println(java.lang.String)
106 */
107 public final static PrintStream out = null;
108
109 /**
110 * The "standard" error output stream. This stream is already
111 * open and ready to accept output data.
112 * <p>
113 * Typically this stream corresponds to display output or another
114 * output destination specified by the host environment or user. By
115 * convention, this output stream is used to display error messages
116 * or other information that should come to the immediate attention
117 * of a user even if the principal output stream, the value of the
118 * variable <code>out</code>, has been redirected to a file or other
119 * destination that is typically not continuously monitored.
120 */
121 public final static PrintStream err = null;
122
123 /* The security manager for the system.
124 */
125 private static volatile SecurityManager security = null;
126
127 /**
128 * Reassigns the "standard" input stream.
129 *
130 * <p>First, if there is a security manager, its <code>checkPermission</code>
131 * method is called with a <code>RuntimePermission("setIO")</code> permission
132 * to see if it's ok to reassign the "standard" input stream.
133 * <p>
134 *
135 * @param in the new standard input stream.
136 *
137 * @throws SecurityException
138 * if a security manager exists and its
139 * <code>checkPermission</code> method doesn't allow
140 * reassigning of the standard input stream.
141 *
142 * @see SecurityManager#checkPermission
143 * @see java.lang.RuntimePermission
144 *
145 * @since JDK1.1
146 */
147 public static void setIn(InputStream in) {
148 checkIO();
149 setIn0(in);
150 }
151
152 /**
153 * Reassigns the "standard" output stream.
154 *
155 * <p>First, if there is a security manager, its <code>checkPermission</code>
156 * method is called with a <code>RuntimePermission("setIO")</code> permission
157 * to see if it's ok to reassign the "standard" output stream.
158 *
159 * @param out the new standard output stream
160 *
161 * @throws SecurityException
162 * if a security manager exists and its
163 * <code>checkPermission</code> method doesn't allow
164 * reassigning of the standard output stream.
165 *
166 * @see SecurityManager#checkPermission
167 * @see java.lang.RuntimePermission
168 *
169 * @since JDK1.1
170 */
171 public static void setOut(PrintStream out) {
172 checkIO();
173 setOut0(out);
174 }
175
176 /**
177 * Reassigns the "standard" error output stream.
178 *
179 * <p>First, if there is a security manager, its <code>checkPermission</code>
180 * method is called with a <code>RuntimePermission("setIO")</code> permission
181 * to see if it's ok to reassign the "standard" error output stream.
182 *
183 * @param err the new standard error output stream.
184 *
185 * @throws SecurityException
186 * if a security manager exists and its
187 * <code>checkPermission</code> method doesn't allow
188 * reassigning of the standard error output stream.
189 *
190 * @see SecurityManager#checkPermission
191 * @see java.lang.RuntimePermission
192 *
193 * @since JDK1.1
194 */
195 public static void setErr(PrintStream err) {
196 checkIO();
197 setErr0(err);
198 }
199
200 private static volatile Console cons = null;
201 /**
202 * Returns the unique {@link java.io.Console Console} object associated
203 * with the current Java virtual machine, if any.
204 *
205 * @return The system console, if any, otherwise <tt>null</tt>.
206 *
207 * @since 1.6
208 */
209 public static Console console() {
210 if (cons == null) {
211 synchronized (System.class) {
212 cons = sun.misc.SharedSecrets.getJavaIOAccess().console();
213 }
214 }
215 return cons;
216 }
217
218 /**
219 * Returns the channel inherited from the entity that created this
220 * Java virtual machine.
221 *
222 * <p> This method returns the channel obtained by invoking the
223 * {@link java.nio.channels.spi.SelectorProvider#inheritedChannel
224 * inheritedChannel} method of the system-wide default
225 * {@link java.nio.channels.spi.SelectorProvider} object. </p>
226 *
227 * <p> In addition to the network-oriented channels described in
228 * {@link java.nio.channels.spi.SelectorProvider#inheritedChannel
229 * inheritedChannel}, this method may return other kinds of
230 * channels in the future.
231 *
232 * @return The inherited channel, if any, otherwise <tt>null</tt>.
233 *
234 * @throws IOException
235 * If an I/O error occurs
236 *
237 * @throws SecurityException
238 * If a security manager is present and it does not
239 * permit access to the channel.
240 *
241 * @since 1.5
242 */
243 public static Channel inheritedChannel() throws IOException {
244 return SelectorProvider.provider().inheritedChannel();
245 }
246
247 private static void checkIO() {
248 SecurityManager sm = getSecurityManager();
249 if (sm != null) {
250 sm.checkPermission(new RuntimePermission("setIO"));
251 }
252 }
253
254 private static native void setIn0(InputStream in);
255 private static native void setOut0(PrintStream out);
256 private static native void setErr0(PrintStream err);
257
258 /**
259 * Sets the System security.
260 *
261 * <p> If there is a security manager already installed, this method first
262 * calls the security manager's <code>checkPermission</code> method
263 * with a <code>RuntimePermission("setSecurityManager")</code>
264 * permission to ensure it's ok to replace the existing
265 * security manager.
266 * This may result in throwing a <code>SecurityException</code>.
267 *
268 * <p> Otherwise, the argument is established as the current
269 * security manager. If the argument is <code>null</code> and no
270 * security manager has been established, then no action is taken and
271 * the method simply returns.
272 *
273 * @param s the security manager.
274 * @exception SecurityException if the security manager has already
275 * been set and its <code>checkPermission</code> method
276 * doesn't allow it to be replaced.
277 * @see #getSecurityManager
278 * @see SecurityManager#checkPermission
279 * @see java.lang.RuntimePermission
280 */
281 public static
282 void setSecurityManager(final SecurityManager s) {
283 try {
284 s.checkPackageAccess("java.lang");
285 } catch (Exception e) {
286 // no-op
287 }
288 setSecurityManager0(s);
289 }
290
291 private static synchronized
292 void setSecurityManager0(final SecurityManager s) {
293 SecurityManager sm = getSecurityManager();
294 if (sm != null) {
295 // ask the currently installed security manager if we
296 // can replace it.
297 sm.checkPermission(new RuntimePermission
298 ("setSecurityManager"));
299 }
300
301 if ((s != null) && (s.getClass().getClassLoader() != null)) {
302 // New security manager class is not on bootstrap classpath.
303 // Cause policy to get initialized before we install the new
304 // security manager, in order to prevent infinite loops when
305 // trying to initialize the policy (which usually involves
306 // accessing some security and/or system properties, which in turn
307 // calls the installed security manager's checkPermission method
308 // which will loop infinitely if there is a non-system class
309 // (in this case: the new security manager class) on the stack).
310 AccessController.doPrivileged(new PrivilegedAction<Object>() {
311 public Object run() {
312 s.getClass().getProtectionDomain().implies
313 (SecurityConstants.ALL_PERMISSION);
314 return null;
315 }
316 });
317 }
318
319 security = s;
320 }
321
322 /**
323 * Gets the system security interface.
324 *
325 * @return if a security manager has already been established for the
326 * current application, then that security manager is returned;
327 * otherwise, <code>null</code> is returned.
328 * @see #setSecurityManager
329 */
330 public static SecurityManager getSecurityManager() {
331 return security;
332 }
333
334 /**
335 * Returns the current time in milliseconds. Note that
336 * while the unit of time of the return value is a millisecond,
337 * the granularity of the value depends on the underlying
338 * operating system and may be larger. For example, many
339 * operating systems measure time in units of tens of
340 * milliseconds.
341 *
342 * <p> See the description of the class <code>Date</code> for
343 * a discussion of slight discrepancies that may arise between
344 * "computer time" and coordinated universal time (UTC).
345 *
346 * @return the difference, measured in milliseconds, between
347 * the current time and midnight, January 1, 1970 UTC.
348 * @see java.util.Date
349 */
350 public static native long currentTimeMillis();
351
352 /**
353 * Returns the current value of the running Java Virtual Machine's
354 * high-resolution time source, in nanoseconds.
355 *
356 * <p>This method can only be used to measure elapsed time and is
357 * not related to any other notion of system or wall-clock time.
358 * The value returned represents nanoseconds since some fixed but
359 * arbitrary <i>origin</i> time (perhaps in the future, so values
360 * may be negative). The same origin is used by all invocations of
361 * this method in an instance of a Java virtual machine; other
362 * virtual machine instances are likely to use a different origin.
363 *
364 * <p>This method provides nanosecond precision, but not necessarily
365 * nanosecond resolution (that is, how frequently the value changes)
366 * - no guarantees are made except that the resolution is at least as
367 * good as that of {@link #currentTimeMillis()}.
368 *
369 * <p>Differences in successive calls that span greater than
370 * approximately 292 years (2<sup>63</sup> nanoseconds) will not
371 * correctly compute elapsed time due to numerical overflow.
372 *
373 * <p>The values returned by this method become meaningful only when
374 * the difference between two such values, obtained within the same
375 * instance of a Java virtual machine, is computed.
376 *
377 * <p> For example, to measure how long some code takes to execute:
378 * <pre> {@code
379 * long startTime = System.nanoTime();
380 * // ... the code being measured ...
381 * long estimatedTime = System.nanoTime() - startTime;}</pre>
382 *
383 * <p>To compare two nanoTime values
384 * <pre> {@code
385 * long t0 = System.nanoTime();
386 * ...
387 * long t1 = System.nanoTime();}</pre>
388 *
389 * one should use {@code t1 - t0 < 0}, not {@code t1 < t0},
390 * because of the possibility of numerical overflow.
391 *
392 * @return the current value of the running Java Virtual Machine's
393 * high-resolution time source, in nanoseconds
394 * @since 1.5
395 */
396 public static native long nanoTime();
397
398 /**
399 * Copies an array from the specified source array, beginning at the
400 * specified position, to the specified position of the destination array.
401 * A subsequence of array components are copied from the source
402 * array referenced by <code>src</code> to the destination array
403 * referenced by <code>dest</code>. The number of components copied is
404 * equal to the <code>length</code> argument. The components at
405 * positions <code>srcPos</code> through
406 * <code>srcPos+length-1</code> in the source array are copied into
407 * positions <code>destPos</code> through
408 * <code>destPos+length-1</code>, respectively, of the destination
409 * array.
410 * <p>
411 * If the <code>src</code> and <code>dest</code> arguments refer to the
412 * same array object, then the copying is performed as if the
413 * components at positions <code>srcPos</code> through
414 * <code>srcPos+length-1</code> were first copied to a temporary
415 * array with <code>length</code> components and then the contents of
416 * the temporary array were copied into positions
417 * <code>destPos</code> through <code>destPos+length-1</code> of the
418 * destination array.
419 * <p>
420 * If <code>dest</code> is <code>null</code>, then a
421 * <code>NullPointerException</code> is thrown.
422 * <p>
423 * If <code>src</code> is <code>null</code>, then a
424 * <code>NullPointerException</code> is thrown and the destination
425 * array is not modified.
426 * <p>
427 * Otherwise, if any of the following is true, an
428 * <code>ArrayStoreException</code> is thrown and the destination is
429 * not modified:
430 * <ul>
431 * <li>The <code>src</code> argument refers to an object that is not an
432 * array.
433 * <li>The <code>dest</code> argument refers to an object that is not an
434 * array.
435 * <li>The <code>src</code> argument and <code>dest</code> argument refer
436 * to arrays whose component types are different primitive types.
437 * <li>The <code>src</code> argument refers to an array with a primitive
438 * component type and the <code>dest</code> argument refers to an array
439 * with a reference component type.
440 * <li>The <code>src</code> argument refers to an array with a reference
441 * component type and the <code>dest</code> argument refers to an array
442 * with a primitive component type.
443 * </ul>
444 * <p>
445 * Otherwise, if any of the following is true, an
446 * <code>IndexOutOfBoundsException</code> is
447 * thrown and the destination is not modified:
448 * <ul>
449 * <li>The <code>srcPos</code> argument is negative.
450 * <li>The <code>destPos</code> argument is negative.
451 * <li>The <code>length</code> argument is negative.
452 * <li><code>srcPos+length</code> is greater than
453 * <code>src.length</code>, the length of the source array.
454 * <li><code>destPos+length</code> is greater than
455 * <code>dest.length</code>, the length of the destination array.
456 * </ul>
457 * <p>
458 * Otherwise, if any actual component of the source array from
459 * position <code>srcPos</code> through
460 * <code>srcPos+length-1</code> cannot be converted to the component
461 * type of the destination array by assignment conversion, an
462 * <code>ArrayStoreException</code> is thrown. In this case, let
463 * <b><i>k</i></b> be the smallest nonnegative integer less than
464 * length such that <code>src[srcPos+</code><i>k</i><code>]</code>
465 * cannot be converted to the component type of the destination
466 * array; when the exception is thrown, source array components from
467 * positions <code>srcPos</code> through
468 * <code>srcPos+</code><i>k</i><code>-1</code>
469 * will already have been copied to destination array positions
470 * <code>destPos</code> through
471 * <code>destPos+</code><i>k</I><code>-1</code> and no other
472 * positions of the destination array will have been modified.
473 * (Because of the restrictions already itemized, this
474 * paragraph effectively applies only to the situation where both
475 * arrays have component types that are reference types.)
476 *
477 * @param src the source array.
478 * @param srcPos starting position in the source array.
479 * @param dest the destination array.
480 * @param destPos starting position in the destination data.
481 * @param length the number of array elements to be copied.
482 * @exception IndexOutOfBoundsException if copying would cause
483 * access of data outside array bounds.
484 * @exception ArrayStoreException if an element in the <code>src</code>
485 * array could not be stored into the <code>dest</code> array
486 * because of a type mismatch.
487 * @exception NullPointerException if either <code>src</code> or
488 * <code>dest</code> is <code>null</code>.
489 */
490 public static native void arraycopy(Object src, int srcPos,
491 Object dest, int destPos,
492 int length);
493
494 /**
495 * Returns the same hash code for the given object as
496 * would be returned by the default method hashCode(),
497 * whether or not the given object's class overrides
498 * hashCode().
499 * The hash code for the null reference is zero.
500 *
501 * @param x object for which the hashCode is to be calculated
502 * @return the hashCode
503 * @since JDK1.1
504 */
505 public static native int identityHashCode(Object x);
506
507 /**
508 * System properties. The following properties are guaranteed to be defined:
509 * <dl>
510 * <dt>java.version <dd>Java version number
511 * <dt>java.vendor <dd>Java vendor specific string
512 * <dt>java.vendor.url <dd>Java vendor URL
513 * <dt>java.home <dd>Java installation directory
514 * <dt>java.class.version <dd>Java class version number
515 * <dt>java.class.path <dd>Java classpath
516 * <dt>os.name <dd>Operating System Name
517 * <dt>os.arch <dd>Operating System Architecture
518 * <dt>os.version <dd>Operating System Version
519 * <dt>file.separator <dd>File separator ("/" on Unix)
520 * <dt>path.separator <dd>Path separator (":" on Unix)
521 * <dt>line.separator <dd>Line separator ("\n" on Unix)
522 * <dt>user.name <dd>User account name
523 * <dt>user.home <dd>User home directory
524 * <dt>user.dir <dd>User's current working directory
525 * </dl>
526 */
527
528 private static Properties props;
529 private static native Properties initProperties(Properties props);
530
531 /**
532 * Determines the current system properties.
533 * <p>
534 * First, if there is a security manager, its
535 * <code>checkPropertiesAccess</code> method is called with no
536 * arguments. This may result in a security exception.
537 * <p>
538 * The current set of system properties for use by the
539 * {@link #getProperty(String)} method is returned as a
540 * <code>Properties</code> object. If there is no current set of
541 * system properties, a set of system properties is first created and
542 * initialized. This set of system properties always includes values
543 * for the following keys:
544 * <table summary="Shows property keys and associated values">
545 * <tr><th>Key</th>
546 * <th>Description of Associated Value</th></tr>
547 * <tr><td><code>java.version</code></td>
548 * <td>Java Runtime Environment version</td></tr>
549 * <tr><td><code>java.vendor</code></td>
550 * <td>Java Runtime Environment vendor</td></tr
551 * <tr><td><code>java.vendor.url</code></td>
552 * <td>Java vendor URL</td></tr>
553 * <tr><td><code>java.home</code></td>
554 * <td>Java installation directory</td></tr>
555 * <tr><td><code>java.vm.specification.version</code></td>
556 * <td>Java Virtual Machine specification version</td></tr>
557 * <tr><td><code>java.vm.specification.vendor</code></td>
558 * <td>Java Virtual Machine specification vendor</td></tr>
559 * <tr><td><code>java.vm.specification.name</code></td>
560 * <td>Java Virtual Machine specification name</td></tr>
561 * <tr><td><code>java.vm.version</code></td>
562 * <td>Java Virtual Machine implementation version</td></tr>
563 * <tr><td><code>java.vm.vendor</code></td>
564 * <td>Java Virtual Machine implementation vendor</td></tr>
565 * <tr><td><code>java.vm.name</code></td>
566 * <td>Java Virtual Machine implementation name</td></tr>
567 * <tr><td><code>java.specification.version</code></td>
568 * <td>Java Runtime Environment specification version</td></tr>
569 * <tr><td><code>java.specification.vendor</code></td>
570 * <td>Java Runtime Environment specification vendor</td></tr>
571 * <tr><td><code>java.specification.name</code></td>
572 * <td>Java Runtime Environment specification name</td></tr>
573 * <tr><td><code>java.class.version</code></td>
574 * <td>Java class format version number</td></tr>
575 * <tr><td><code>java.class.path</code></td>
576 * <td>Java class path</td></tr>
577 * <tr><td><code>java.library.path</code></td>
578 * <td>List of paths to search when loading libraries</td></tr>
579 * <tr><td><code>java.io.tmpdir</code></td>
580 * <td>Default temp file path</td></tr>
581 * <tr><td><code>java.compiler</code></td>
582 * <td>Name of JIT compiler to use</td></tr>
583 * <tr><td><code>java.ext.dirs</code></td>
584 * <td>Path of extension directory or directories</td></tr>
585 * <tr><td><code>os.name</code></td>
586 * <td>Operating system name</td></tr>
587 * <tr><td><code>os.arch</code></td>
588 * <td>Operating system architecture</td></tr>
589 * <tr><td><code>os.version</code></td>
590 * <td>Operating system version</td></tr>
591 * <tr><td><code>file.separator</code></td>
592 * <td>File separator ("/" on UNIX)</td></tr>
593 * <tr><td><code>path.separator</code></td>
594 * <td>Path separator (":" on UNIX)</td></tr>
595 * <tr><td><code>line.separator</code></td>
596 * <td>Line separator ("\n" on UNIX)</td></tr>
597 * <tr><td><code>user.name</code></td>
598 * <td>User's account name</td></tr>
599 * <tr><td><code>user.home</code></td>
600 * <td>User's home directory</td></tr>
601 * <tr><td><code>user.dir</code></td>
602 * <td>User's current working directory</td></tr>
603 * </table>
604 * <p>
605 * Multiple paths in a system property value are separated by the path
606 * separator character of the platform.
607 * <p>
608 * Note that even if the security manager does not permit the
609 * <code>getProperties</code> operation, it may choose to permit the
610 * {@link #getProperty(String)} operation.
611 *
612 * @return the system properties
613 * @exception SecurityException if a security manager exists and its
614 * <code>checkPropertiesAccess</code> method doesn't allow access
615 * to the system properties.
616 * @see #setProperties
617 * @see java.lang.SecurityException
618 * @see java.lang.SecurityManager#checkPropertiesAccess()
619 * @see java.util.Properties
620 */
621 public static Properties getProperties() {
622 SecurityManager sm = getSecurityManager();
623 if (sm != null) {
624 sm.checkPropertiesAccess();
625 }
626
627 return props;
628 }
629
630 /**
631 * Returns the system-dependent line separator string. It always
632 * returns the same value - the initial value of the {@linkplain
633 * #getProperty(String) system property} {@code line.separator}.
634 *
635 * <p>On UNIX systems, it returns {@code "\n"}; on Microsoft
636 * Windows systems it returns {@code "\r\n"}.
637 */
638 public static String lineSeparator() {
639 return lineSeparator;
640 }
641
642 private static String lineSeparator;
643
644 /**
645 * Sets the system properties to the <code>Properties</code>
646 * argument.
647 * <p>
648 * First, if there is a security manager, its
649 * <code>checkPropertiesAccess</code> method is called with no
650 * arguments. This may result in a security exception.
651 * <p>
652 * The argument becomes the current set of system properties for use
653 * by the {@link #getProperty(String)} method. If the argument is
654 * <code>null</code>, then the current set of system properties is
655 * forgotten.
656 *
657 * @param props the new system properties.
658 * @exception SecurityException if a security manager exists and its
659 * <code>checkPropertiesAccess</code> method doesn't allow access
660 * to the system properties.
661 * @see #getProperties
662 * @see java.util.Properties
663 * @see java.lang.SecurityException
664 * @see java.lang.SecurityManager#checkPropertiesAccess()
665 */
666 public static void setProperties(Properties props) {
667 SecurityManager sm = getSecurityManager();
668 if (sm != null) {
669 sm.checkPropertiesAccess();
670 }
671 if (props == null) {
672 props = new Properties();
673 initProperties(props);
674 }
675 System.props = props;
676 }
677
678 /**
679 * Gets the system property indicated by the specified key.
680 * <p>
681 * First, if there is a security manager, its
682 * <code>checkPropertyAccess</code> method is called with the key as
683 * its argument. This may result in a SecurityException.
684 * <p>
685 * If there is no current set of system properties, a set of system
686 * properties is first created and initialized in the same manner as
687 * for the <code>getProperties</code> method.
688 *
689 * @param key the name of the system property.
690 * @return the string value of the system property,
691 * or <code>null</code> if there is no property with that key.
692 *
693 * @exception SecurityException if a security manager exists and its
694 * <code>checkPropertyAccess</code> method doesn't allow
695 * access to the specified system property.
696 * @exception NullPointerException if <code>key</code> is
697 * <code>null</code>.
698 * @exception IllegalArgumentException if <code>key</code> is empty.
699 * @see #setProperty
700 * @see java.lang.SecurityException
701 * @see java.lang.SecurityManager#checkPropertyAccess(java.lang.String)
702 * @see java.lang.System#getProperties()
703 */
704 public static String getProperty(String key) {
705 checkKey(key);
706 SecurityManager sm = getSecurityManager();
707 if (sm != null) {
708 sm.checkPropertyAccess(key);
709 }
710
711 return props.getProperty(key);
712 }
713
714 /**
715 * Gets the system property indicated by the specified key.
716 * <p>
717 * First, if there is a security manager, its
718 * <code>checkPropertyAccess</code> method is called with the
719 * <code>key</code> as its argument.
720 * <p>
721 * If there is no current set of system properties, a set of system
722 * properties is first created and initialized in the same manner as
723 * for the <code>getProperties</code> method.
724 *
725 * @param key the name of the system property.
726 * @param def a default value.
727 * @return the string value of the system property,
728 * or the default value if there is no property with that key.
729 *
730 * @exception SecurityException if a security manager exists and its
731 * <code>checkPropertyAccess</code> method doesn't allow
732 * access to the specified system property.
733 * @exception NullPointerException if <code>key</code> is
734 * <code>null</code>.
735 * @exception IllegalArgumentException if <code>key</code> is empty.
736 * @see #setProperty
737 * @see java.lang.SecurityManager#checkPropertyAccess(java.lang.String)
738 * @see java.lang.System#getProperties()
739 */
740 public static String getProperty(String key, String def) {
741 checkKey(key);
742 SecurityManager sm = getSecurityManager();
743 if (sm != null) {
744 sm.checkPropertyAccess(key);
745 }
746
747 return props.getProperty(key, def);
748 }
749
750 /**
751 * Sets the system property indicated by the specified key.
752 * <p>
753 * First, if a security manager exists, its
754 * <code>SecurityManager.checkPermission</code> method
755 * is called with a <code>PropertyPermission(key, "write")</code>
756 * permission. This may result in a SecurityException being thrown.
757 * If no exception is thrown, the specified property is set to the given
758 * value.
759 * <p>
760 *
761 * @param key the name of the system property.
762 * @param value the value of the system property.
763 * @return the previous value of the system property,
764 * or <code>null</code> if it did not have one.
765 *
766 * @exception SecurityException if a security manager exists and its
767 * <code>checkPermission</code> method doesn't allow
768 * setting of the specified property.
769 * @exception NullPointerException if <code>key</code> or
770 * <code>value</code> is <code>null</code>.
771 * @exception IllegalArgumentException if <code>key</code> is empty.
772 * @see #getProperty
773 * @see java.lang.System#getProperty(java.lang.String)
774 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
775 * @see java.util.PropertyPermission
776 * @see SecurityManager#checkPermission
777 * @since 1.2
778 */
779 public static String setProperty(String key, String value) {
780 checkKey(key);
781 SecurityManager sm = getSecurityManager();
782 if (sm != null) {
783 sm.checkPermission(new PropertyPermission(key,
784 SecurityConstants.PROPERTY_WRITE_ACTION));
785 }
786
787 return (String) props.setProperty(key, value);
788 }
789
790 /**
791 * Removes the system property indicated by the specified key.
792 * <p>
793 * First, if a security manager exists, its
794 * <code>SecurityManager.checkPermission</code> method
795 * is called with a <code>PropertyPermission(key, "write")</code>
796 * permission. This may result in a SecurityException being thrown.
797 * If no exception is thrown, the specified property is removed.
798 * <p>
799 *
800 * @param key the name of the system property to be removed.
801 * @return the previous string value of the system property,
802 * or <code>null</code> if there was no property with that key.
803 *
804 * @exception SecurityException if a security manager exists and its
805 * <code>checkPropertyAccess</code> method doesn't allow
806 * access to the specified system property.
807 * @exception NullPointerException if <code>key</code> is
808 * <code>null</code>.
809 * @exception IllegalArgumentException if <code>key</code> is empty.
810 * @see #getProperty
811 * @see #setProperty
812 * @see java.util.Properties
813 * @see java.lang.SecurityException
814 * @see java.lang.SecurityManager#checkPropertiesAccess()
815 * @since 1.5
816 */
817 public static String clearProperty(String key) {
818 checkKey(key);
819 SecurityManager sm = getSecurityManager();
820 if (sm != null) {
821 sm.checkPermission(new PropertyPermission(key, "write"));
822 }
823
824 return (String) props.remove(key);
825 }
826
827 private static void checkKey(String key) {
828 if (key == null) {
829 throw new NullPointerException("key can't be null");
830 }
831 if (key.equals("")) {
832 throw new IllegalArgumentException("key can't be empty");
833 }
834 }
835
836 /**
837 * Gets the value of the specified environment variable. An
838 * environment variable is a system-dependent external named
839 * value.
840 *
841 * <p>If a security manager exists, its
842 * {@link SecurityManager#checkPermission checkPermission}
843 * method is called with a
844 * <code>{@link RuntimePermission}("getenv."+name)</code>
845 * permission. This may result in a {@link SecurityException}
846 * being thrown. If no exception is thrown the value of the
847 * variable <code>name</code> is returned.
848 *
849 * <p><a name="EnvironmentVSSystemProperties"><i>System
850 * properties</i> and <i>environment variables</i></a> are both
851 * conceptually mappings between names and values. Both
852 * mechanisms can be used to pass user-defined information to a
853 * Java process. Environment variables have a more global effect,
854 * because they are visible to all descendants of the process
855 * which defines them, not just the immediate Java subprocess.
856 * They can have subtly different semantics, such as case
857 * insensitivity, on different operating systems. For these
858 * reasons, environment variables are more likely to have
859 * unintended side effects. It is best to use system properties
860 * where possible. Environment variables should be used when a
861 * global effect is desired, or when an external system interface
862 * requires an environment variable (such as <code>PATH</code>).
863 *
864 * <p>On UNIX systems the alphabetic case of <code>name</code> is
865 * typically significant, while on Microsoft Windows systems it is
866 * typically not. For example, the expression
867 * <code>System.getenv("FOO").equals(System.getenv("foo"))</code>
868 * is likely to be true on Microsoft Windows.
869 *
870 * @param name the name of the environment variable
871 * @return the string value of the variable, or <code>null</code>
872 * if the variable is not defined in the system environment
873 * @throws NullPointerException if <code>name</code> is <code>null</code>
874 * @throws SecurityException
875 * if a security manager exists and its
876 * {@link SecurityManager#checkPermission checkPermission}
877 * method doesn't allow access to the environment variable
878 * <code>name</code>
879 * @see #getenv()
880 * @see ProcessBuilder#environment()
881 */
882 public static String getenv(String name) {
883 SecurityManager sm = getSecurityManager();
884 if (sm != null) {
885 sm.checkPermission(new RuntimePermission("getenv."+name));
886 }
887
888 return ProcessEnvironment.getenv(name);
889 }
890
891
892 /**
893 * Returns an unmodifiable string map view of the current system environment.
894 * The environment is a system-dependent mapping from names to
895 * values which is passed from parent to child processes.
896 *
897 * <p>If the system does not support environment variables, an
898 * empty map is returned.
899 *
900 * <p>The returned map will never contain null keys or values.
901 * Attempting to query the presence of a null key or value will
902 * throw a {@link NullPointerException}. Attempting to query
903 * the presence of a key or value which is not of type
904 * {@link String} will throw a {@link ClassCastException}.
905 *
906 * <p>The returned map and its collection views may not obey the
907 * general contract of the {@link Object#equals} and
908 * {@link Object#hashCode} methods.
909 *
910 * <p>The returned map is typically case-sensitive on all platforms.
911 *
912 * <p>If a security manager exists, its
913 * {@link SecurityManager#checkPermission checkPermission}
914 * method is called with a
915 * <code>{@link RuntimePermission}("getenv.*")</code>
916 * permission. This may result in a {@link SecurityException} being
917 * thrown.
918 *
919 * <p>When passing information to a Java subprocess,
920 * <a href=#EnvironmentVSSystemProperties>system properties</a>
921 * are generally preferred over environment variables.
922 *
923 * @return the environment as a map of variable names to values
924 * @throws SecurityException
925 * if a security manager exists and its
926 * {@link SecurityManager#checkPermission checkPermission}
927 * method doesn't allow access to the process environment
928 * @see #getenv(String)
929 * @see ProcessBuilder#environment()
930 * @since 1.5
931 */
932 public static java.util.Map<String,String> getenv() {
933 SecurityManager sm = getSecurityManager();
934 if (sm != null) {
935 sm.checkPermission(new RuntimePermission("getenv.*"));
936 }
937
938 return ProcessEnvironment.getenv();
939 }
940
941 /**
942 * Terminates the currently running Java Virtual Machine. The
943 * argument serves as a status code; by convention, a nonzero status
944 * code indicates abnormal termination.
945 * <p>
946 * This method calls the <code>exit</code> method in class
947 * <code>Runtime</code>. This method never returns normally.
948 * <p>
949 * The call <code>System.exit(n)</code> is effectively equivalent to
950 * the call:
951 * <blockquote><pre>
952 * Runtime.getRuntime().exit(n)
953 * </pre></blockquote>
954 *
955 * @param status exit status.
956 * @throws SecurityException
957 * if a security manager exists and its <code>checkExit</code>
958 * method doesn't allow exit with the specified status.
959 * @see java.lang.Runtime#exit(int)
960 */
961 public static void exit(int status) {
962 Runtime.getRuntime().exit(status);
963 }
964
965 /**
966 * Runs the garbage collector.
967 * <p>
968 * Calling the <code>gc</code> method suggests that the Java Virtual
969 * Machine expend effort toward recycling unused objects in order to
970 * make the memory they currently occupy available for quick reuse.
971 * When control returns from the method call, the Java Virtual
972 * Machine has made a best effort to reclaim space from all discarded
973 * objects.
974 * <p>
975 * The call <code>System.gc()</code> is effectively equivalent to the
976 * call:
977 * <blockquote><pre>
978 * Runtime.getRuntime().gc()
979 * </pre></blockquote>
980 *
981 * @see java.lang.Runtime#gc()
982 */
983 public static void gc() {
984 Runtime.getRuntime().gc();
985 }
986
987 /**
988 * Runs the finalization methods of any objects pending finalization.
989 * <p>
990 * Calling this method suggests that the Java Virtual Machine expend
991 * effort toward running the <code>finalize</code> methods of objects
992 * that have been found to be discarded but whose <code>finalize</code>
993 * methods have not yet been run. When control returns from the
994 * method call, the Java Virtual Machine has made a best effort to
995 * complete all outstanding finalizations.
996 * <p>
997 * The call <code>System.runFinalization()</code> is effectively
998 * equivalent to the call:
999 * <blockquote><pre>
1000 * Runtime.getRuntime().runFinalization()
1001 * </pre></blockquote>
1002 *
1003 * @see java.lang.Runtime#runFinalization()
1004 */
1005 public static void runFinalization() {
1006 Runtime.getRuntime().runFinalization();
1007 }
1008
1009 /**
1010 * Enable or disable finalization on exit; doing so specifies that the
1011 * finalizers of all objects that have finalizers that have not yet been
1012 * automatically invoked are to be run before the Java runtime exits.
1013 * By default, finalization on exit is disabled.
1014 *
1015 * <p>If there is a security manager,
1016 * its <code>checkExit</code> method is first called
1017 * with 0 as its argument to ensure the exit is allowed.
1018 * This could result in a SecurityException.
1019 *
1020 * @deprecated This method is inherently unsafe. It may result in
1021 * finalizers being called on live objects while other threads are
1022 * concurrently manipulating those objects, resulting in erratic
1023 * behavior or deadlock.
1024 * @param value indicating enabling or disabling of finalization
1025 * @throws SecurityException
1026 * if a security manager exists and its <code>checkExit</code>
1027 * method doesn't allow the exit.
1028 *
1029 * @see java.lang.Runtime#exit(int)
1030 * @see java.lang.Runtime#gc()
1031 * @see java.lang.SecurityManager#checkExit(int)
1032 * @since JDK1.1
1033 */
1034 @Deprecated
1035 public static void runFinalizersOnExit(boolean value) {
1036 Runtime.getRuntime().runFinalizersOnExit(value);
1037 }
1038
1039 /**
1040 * Loads a code file with the specified filename from the local file
1041 * system as a dynamic library. The filename
1042 * argument must be a complete path name.
1043 * <p>
1044 * The call <code>System.load(name)</code> is effectively equivalent
1045 * to the call:
1046 * <blockquote><pre>
1047 * Runtime.getRuntime().load(name)
1048 * </pre></blockquote>
1049 *
1050 * @param filename the file to load.
1051 * @exception SecurityException if a security manager exists and its
1052 * <code>checkLink</code> method doesn't allow
1053 * loading of the specified dynamic library
1054 * @exception UnsatisfiedLinkError if the file does not exist.
1055 * @exception NullPointerException if <code>filename</code> is
1056 * <code>null</code>
1057 * @see java.lang.Runtime#load(java.lang.String)
1058 * @see java.lang.SecurityManager#checkLink(java.lang.String)
1059 */
1060 @CallerSensitive
1061 public static void load(String filename) {
1062 Runtime.getRuntime().load0(Reflection.getCallerClass(), filename);
1063 }
1064
1065 /**
1066 * Loads the system library specified by the <code>libname</code>
1067 * argument. The manner in which a library name is mapped to the
1068 * actual system library is system dependent.
1069 * <p>
1070 * The call <code>System.loadLibrary(name)</code> is effectively
1071 * equivalent to the call
1072 * <blockquote><pre>
1073 * Runtime.getRuntime().loadLibrary(name)
1074 * </pre></blockquote>
1075 *
1076 * @param libname the name of the library.
1077 * @exception SecurityException if a security manager exists and its
1078 * <code>checkLink</code> method doesn't allow
1079 * loading of the specified dynamic library
1080 * @exception UnsatisfiedLinkError if the library does not exist.
1081 * @exception NullPointerException if <code>libname</code> is
1082 * <code>null</code>
1083 * @see java.lang.Runtime#loadLibrary(java.lang.String)
1084 * @see java.lang.SecurityManager#checkLink(java.lang.String)
1085 */
1086 @CallerSensitive
1087 public static void loadLibrary(String libname) {
1088 Runtime.getRuntime().loadLibrary0(Reflection.getCallerClass(), libname);
1089 }
1090
1091 /**
1092 * Maps a library name into a platform-specific string representing
1093 * a native library.
1094 *
1095 * @param libname the name of the library.
1096 * @return a platform-dependent native library name.
1097 * @exception NullPointerException if <code>libname</code> is
1098 * <code>null</code>
1099 * @see java.lang.System#loadLibrary(java.lang.String)
1100 * @see java.lang.ClassLoader#findLibrary(java.lang.String)
1101 * @since 1.2
1102 */
1103 public static native String mapLibraryName(String libname);
1104
1105 /**
1106 * Initialize the system class. Called after thread initialization.
1107 */
1108 private static void initializeSystemClass() {
1109
1110 // VM might invoke JNU_NewStringPlatform() to set those encoding
1111 // sensitive properties (user.home, user.name, boot.class.path, etc.)
1112 // during "props" initialization, in which it may need access, via
1113 // System.getProperty(), to the related system encoding property that
1114 // have been initialized (put into "props") at early stage of the
1115 // initialization. So make sure the "props" is available at the
1116 // very beginning of the initialization and all system properties to
1117 // be put into it directly.
1118 props = new Properties();
1119 initProperties(props); // initialized by the VM
1120
1121 // There are certain system configurations that may be controlled by
1122 // VM options such as the maximum amount of direct memory and
1123 // Integer cache size used to support the object identity semantics
1124 // of autoboxing. Typically, the library will obtain these values
1125 // from the properties set by the VM. If the properties are for
1126 // internal implementation use only, these properties should be
1127 // removed from the system properties.
1128 //
1129 // See java.lang.Integer.IntegerCache and the
1130 // sun.misc.VM.saveAndRemoveProperties method for example.
1131 //
1132 // Save a private copy of the system properties object that
1133 // can only be accessed by the internal implementation. Remove
1134 // certain system properties that are not intended for public access.
1135 sun.misc.VM.saveAndRemoveProperties(props);
1136
1137
1138 lineSeparator = props.getProperty("line.separator");
1139 sun.misc.Version.init();
1140
1141 FileInputStream fdIn = new FileInputStream(FileDescriptor.in);
1142 FileOutputStream fdOut = new FileOutputStream(FileDescriptor.out);
1143 FileOutputStream fdErr = new FileOutputStream(FileDescriptor.err);
1144 setIn0(new BufferedInputStream(fdIn));
1145 setOut0(new PrintStream(new BufferedOutputStream(fdOut, 128), true));
1146 setErr0(new PrintStream(new BufferedOutputStream(fdErr, 128), true));
1147 // Load the zip library now in order to keep java.util.zip.ZipFile
1148 // from trying to use itself to load this library later.
1149 loadLibrary("zip");
1150
1151 // Setup Java signal handlers for HUP, TERM, and INT (where available).
1152 Terminator.setup();
1153
1154 // Initialize any miscellenous operating system settings that need to be
1155 // set for the class libraries. Currently this is no-op everywhere except
1156 // for Windows where the process-wide error mode is set before the java.io
1157 // classes are used.
1158 sun.misc.VM.initializeOSEnvironment();
1159
1160 // The main thread is not added to its thread group in the same
1161 // way as other threads; we must do it ourselves here.
1162 Thread current = Thread.currentThread();
1163 current.getThreadGroup().add(current);
1164
1165 // register shared secrets
1166 setJavaLangAccess();
1167
1168 // Subsystems that are invoked during initialization can invoke
1169 // sun.misc.VM.isBooted() in order to avoid doing things that should
1170 // wait until the application class loader has been set up.
1171 // IMPORTANT: Ensure that this remains the last initialization action!
1172 sun.misc.VM.booted();
1173 }
1174
1175 private static void setJavaLangAccess() {
1176 // Allow privileged classes outside of java.lang
1177 sun.misc.SharedSecrets.setJavaLangAccess(new sun.misc.JavaLangAccess(){
1178 public sun.reflect.ConstantPool getConstantPool(Class klass) {
1179 return klass.getConstantPool();
1180 }
1181 public void setAnnotationType(Class klass, AnnotationType type) {
1182 klass.setAnnotationType(type);
1183 }
1184 public AnnotationType getAnnotationType(Class klass) {
1185 return klass.getAnnotationType();
1186 }
1187 public <E extends Enum<E>>
1188 E[] getEnumConstantsShared(Class<E> klass) {
1189 return klass.getEnumConstantsShared();
1190 }
1191 public void blockedOn(Thread t, Interruptible b) {
1192 t.blockedOn(b);
1193 }
1194 public void registerShutdownHook(int slot, boolean registerShutdownInProgress, Runnable hook) {
1195 Shutdown.add(slot, registerShutdownInProgress, hook);
1196 }
1197 public int getStackTraceDepth(Throwable t) {
1198 return t.getStackTraceDepth();
1199 }
1200 public StackTraceElement getStackTraceElement(Throwable t, int i) {
1201 return t.getStackTraceElement(i);
1202 }
1203 public int getStringHash32(String string) {
1204 return string.hash32();
1205 }
1206 public Thread newThreadWithAcc(Runnable target, AccessControlContext acc) {
1207 return new Thread(target, acc);
1208 }
1209 public void invokeFinalize(Object o) throws Throwable {
1210 o.finalize();
1211 }
1212 });
1213 }
1214 }