1 /*
2 * Copyright 1994-2007 Sun Microsystems, Inc. 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. Sun designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 * CA 95054 USA or visit www.sun.com if you need additional information or
23 * have any questions.
24 */
25 package java.lang;
26
27 import java.io.*;
28 import java.util.Properties;
29 import java.util.PropertyPermission;
30 import java.util.StringTokenizer;
31 import java.security.AccessController;
32 import java.security.PrivilegedAction;
33 import java.security.AllPermission;
34 import java.nio.channels.Channel;
35 import java.nio.channels.spi.SelectorProvider;
36 import sun.nio.ch.Interruptible;
37 import sun.net.InetAddressCachePolicy;
38 import sun.reflect.Reflection;
39 import sun.security.util.SecurityConstants;
40 import sun.reflect.annotation.AnnotationType;
41
42 /**
43 * The <code>System</code> class contains several useful class fields
44 * and methods. It cannot be instantiated.
45 *
46 * <p>Among the facilities provided by the <code>System</code> class
47 * are standard input, standard output, and error output streams;
48 * access to externally defined properties and environment
49 * variables; a means of loading files and libraries; and a utility
50 * method for quickly copying a portion of an array.
51 *
52 * @author unascribed
53 * @since JDK1.0
54 */
55 public final class System {
56
57 /* First thing---register the natives */
58 private static native void registerNatives();
59 static {
60 registerNatives();
61 }
62
63 /** Don't let anyone instantiate this class */
64 private System() {
65 }
66
67 /**
68 * The "standard" input stream. This stream is already
69 * open and ready to supply input data. Typically this stream
70 * corresponds to keyboard input or another input source specified by
71 * the host environment or user.
72 */
73 public final static InputStream in = nullInputStream();
74
75 /**
76 * The "standard" output stream. This stream is already
77 * open and ready to accept output data. Typically this stream
78 * corresponds to display output or another output destination
79 * specified by the host environment or user.
80 * <p>
81 * For simple stand-alone Java applications, a typical way to write
82 * a line of output data is:
83 * <blockquote><pre>
84 * System.out.println(data)
85 * </pre></blockquote>
86 * <p>
87 * See the <code>println</code> methods in class <code>PrintStream</code>.
88 *
89 * @see java.io.PrintStream#println()
90 * @see java.io.PrintStream#println(boolean)
91 * @see java.io.PrintStream#println(char)
92 * @see java.io.PrintStream#println(char[])
93 * @see java.io.PrintStream#println(double)
94 * @see java.io.PrintStream#println(float)
95 * @see java.io.PrintStream#println(int)
96 * @see java.io.PrintStream#println(long)
97 * @see java.io.PrintStream#println(java.lang.Object)
98 * @see java.io.PrintStream#println(java.lang.String)
99 */
100 public final static PrintStream out = nullPrintStream();
101
102 /**
103 * The "standard" error output stream. This stream is already
104 * open and ready to accept output data.
105 * <p>
106 * Typically this stream corresponds to display output or another
107 * output destination specified by the host environment or user. By
108 * convention, this output stream is used to display error messages
109 * or other information that should come to the immediate attention
110 * of a user even if the principal output stream, the value of the
111 * variable <code>out</code>, has been redirected to a file or other
112 * destination that is typically not continuously monitored.
113 */
114 public final static PrintStream err = nullPrintStream();
115
116 /* The security manager for the system.
117 */
118 private static volatile SecurityManager security = null;
119
120 /**
121 * Reassigns the "standard" input stream.
122 *
123 * <p>First, if there is a security manager, its <code>checkPermission</code>
124 * method is called with a <code>RuntimePermission("setIO")</code> permission
125 * to see if it's ok to reassign the "standard" input stream.
126 * <p>
127 *
128 * @param in the new standard input stream.
129 *
130 * @throws SecurityException
131 * if a security manager exists and its
132 * <code>checkPermission</code> method doesn't allow
133 * reassigning of the standard input stream.
134 *
135 * @see SecurityManager#checkPermission
136 * @see java.lang.RuntimePermission
137 *
138 * @since JDK1.1
139 */
140 public static void setIn(InputStream in) {
141 checkIO();
142 setIn0(in);
143 }
144
145 /**
146 * Reassigns the "standard" output stream.
147 *
148 * <p>First, if there is a security manager, its <code>checkPermission</code>
149 * method is called with a <code>RuntimePermission("setIO")</code> permission
150 * to see if it's ok to reassign the "standard" output stream.
151 *
152 * @param out the new standard output stream
153 *
154 * @throws SecurityException
155 * if a security manager exists and its
156 * <code>checkPermission</code> method doesn't allow
157 * reassigning of the standard output stream.
158 *
159 * @see SecurityManager#checkPermission
160 * @see java.lang.RuntimePermission
161 *
162 * @since JDK1.1
163 */
164 public static void setOut(PrintStream out) {
165 checkIO();
166 setOut0(out);
167 }
168
169 /**
170 * Reassigns the "standard" error output stream.
171 *
172 * <p>First, if there is a security manager, its <code>checkPermission</code>
173 * method is called with a <code>RuntimePermission("setIO")</code> permission
174 * to see if it's ok to reassign the "standard" error output stream.
175 *
176 * @param err the new standard error output stream.
177 *
178 * @throws SecurityException
179 * if a security manager exists and its
180 * <code>checkPermission</code> method doesn't allow
181 * reassigning of the standard error output stream.
182 *
183 * @see SecurityManager#checkPermission
184 * @see java.lang.RuntimePermission
185 *
186 * @since JDK1.1
187 */
188 public static void setErr(PrintStream err) {
189 checkIO();
190 setErr0(err);
191 }
192
193 private static volatile Console cons = null;
194 /**
195 * Returns the unique {@link java.io.Console Console} object associated
196 * with the current Java virtual machine, if any.
197 *
198 * @return The system console, if any, otherwise <tt>null</tt>.
199 *
200 * @since 1.6
201 */
202 public static Console console() {
203 if (cons == null) {
204 synchronized (System.class) {
205 cons = sun.misc.SharedSecrets.getJavaIOAccess().console();
206 }
207 }
208 return cons;
209 }
210
211 /**
212 * Returns the channel inherited from the entity that created this
213 * Java virtual machine.
214 *
215 * <p> This method returns the channel obtained by invoking the
216 * {@link java.nio.channels.spi.SelectorProvider#inheritedChannel
217 * inheritedChannel} method of the system-wide default
218 * {@link java.nio.channels.spi.SelectorProvider} object. </p>
219 *
220 * <p> In addition to the network-oriented channels described in
221 * {@link java.nio.channels.spi.SelectorProvider#inheritedChannel
222 * inheritedChannel}, this method may return other kinds of
223 * channels in the future.
224 *
225 * @return The inherited channel, if any, otherwise <tt>null</tt>.
226 *
227 * @throws IOException
228 * If an I/O error occurs
229 *
230 * @throws SecurityException
231 * If a security manager is present and it does not
232 * permit access to the channel.
233 *
234 * @since 1.5
235 */
236 public static Channel inheritedChannel() throws IOException {
237 return SelectorProvider.provider().inheritedChannel();
238 }
239
240 private static void checkIO() {
241 SecurityManager sm = getSecurityManager();
242 if (sm != null) {
243 sm.checkPermission(new RuntimePermission("setIO"));
244 }
245 }
246
247 private static native void setIn0(InputStream in);
248 private static native void setOut0(PrintStream out);
249 private static native void setErr0(PrintStream err);
250
251 /**
252 * Sets the System security.
253 *
254 * <p> If there is a security manager already installed, this method first
255 * calls the security manager's <code>checkPermission</code> method
256 * with a <code>RuntimePermission("setSecurityManager")</code>
257 * permission to ensure it's ok to replace the existing
258 * security manager.
259 * This may result in throwing a <code>SecurityException</code>.
260 *
261 * <p> Otherwise, the argument is established as the current
262 * security manager. If the argument is <code>null</code> and no
263 * security manager has been established, then no action is taken and
264 * the method simply returns.
265 *
266 * @param s the security manager.
267 * @exception SecurityException if the security manager has already
268 * been set and its <code>checkPermission</code> method
269 * doesn't allow it to be replaced.
270 * @see #getSecurityManager
271 * @see SecurityManager#checkPermission
272 * @see java.lang.RuntimePermission
273 */
274 public static
275 void setSecurityManager(final SecurityManager s) {
276 try {
277 s.checkPackageAccess("java.lang");
278 } catch (Exception e) {
279 // no-op
280 }
281 setSecurityManager0(s);
282 }
283
284 private static synchronized
285 void setSecurityManager0(final SecurityManager s) {
286 SecurityManager sm = getSecurityManager();
287 if (sm != null) {
288 // ask the currently installed security manager if we
289 // can replace it.
290 sm.checkPermission(new RuntimePermission
291 ("setSecurityManager"));
292 }
293
294 if ((s != null) && (s.getClass().getClassLoader() != null)) {
295 // New security manager class is not on bootstrap classpath.
296 // Cause policy to get initialized before we install the new
297 // security manager, in order to prevent infinite loops when
298 // trying to initialize the policy (which usually involves
299 // accessing some security and/or system properties, which in turn
300 // calls the installed security manager's checkPermission method
301 // which will loop infinitely if there is a non-system class
302 // (in this case: the new security manager class) on the stack).
303 AccessController.doPrivileged(new PrivilegedAction<Object>() {
304 public Object run() {
305 s.getClass().getProtectionDomain().implies
306 (SecurityConstants.ALL_PERMISSION);
307 return null;
308 }
309 });
310 }
311
312 security = s;
313 InetAddressCachePolicy.setIfNotSet(InetAddressCachePolicy.FOREVER);
314 }
315
316 /**
317 * Gets the system security interface.
318 *
319 * @return if a security manager has already been established for the
320 * current application, then that security manager is returned;
321 * otherwise, <code>null</code> is returned.
322 * @see #setSecurityManager
323 */
324 public static SecurityManager getSecurityManager() {
325 return security;
326 }
327
328 /**
329 * Returns the current time in milliseconds. Note that
330 * while the unit of time of the return value is a millisecond,
331 * the granularity of the value depends on the underlying
332 * operating system and may be larger. For example, many
333 * operating systems measure time in units of tens of
334 * milliseconds.
335 *
336 * <p> See the description of the class <code>Date</code> for
337 * a discussion of slight discrepancies that may arise between
338 * "computer time" and coordinated universal time (UTC).
339 *
340 * @return the difference, measured in milliseconds, between
341 * the current time and midnight, January 1, 1970 UTC.
342 * @see java.util.Date
343 */
344 public static native long currentTimeMillis();
345
346 /**
347 * Returns the current value of the running Java Virtual Machine's
348 * high-resolution time source, in nanoseconds.
349 *
350 * <p>This method can only be used to measure elapsed time and is
351 * not related to any other notion of system or wall-clock time.
352 * The value returned represents nanoseconds since some fixed but
353 * arbitrary <i>origin</i> time (perhaps in the future, so values
354 * may be negative). The same origin is used by all invocations of
355 * this method in an instance of a Java virtual machine; other
356 * virtual machine instances are likely to use a different origin.
357 *
358 * <p>This method provides nanosecond precision, but not necessarily
359 * nanosecond resolution (that is, how frequently the value changes)
360 * - no guarantees are made except that the resolution is at least as
361 * good as that of {@link #currentTimeMillis()}.
362 *
363 * <p>Differences in successive calls that span greater than
364 * approximately 292 years (2<sup>63</sup> nanoseconds) will not
365 * correctly compute elapsed time due to numerical overflow.
366 *
367 * <p>The values returned by this method become meaningful only when
368 * the difference between two such values, obtained within the same
369 * instance of a Java virtual machine, is computed.
370 *
371 * <p> For example, to measure how long some code takes to execute:
372 * <pre> {@code
373 * long startTime = System.nanoTime();
374 * // ... the code being measured ...
375 * long estimatedTime = System.nanoTime() - startTime;}</pre>
376 *
377 * <p>To compare two nanoTime values
378 * <pre> {@code
379 * long t0 = System.nanoTime();
380 * ...
381 * long t1 = System.nanoTime();}</pre>
382 *
383 * one should use {@code t1 - t0 < 0}, not {@code t1 < t0},
384 * because of the possibility of numerical overflow.
385 *
386 * @return the current value of the running Java Virtual Machine's
387 * high-resolution time source, in nanoseconds
388 * @since 1.5
389 */
390 public static native long nanoTime();
391
392 /**
393 * Copies an array from the specified source array, beginning at the
394 * specified position, to the specified position of the destination array.
395 * A subsequence of array components are copied from the source
396 * array referenced by <code>src</code> to the destination array
397 * referenced by <code>dest</code>. The number of components copied is
398 * equal to the <code>length</code> argument. The components at
399 * positions <code>srcPos</code> through
400 * <code>srcPos+length-1</code> in the source array are copied into
401 * positions <code>destPos</code> through
402 * <code>destPos+length-1</code>, respectively, of the destination
403 * array.
404 * <p>
405 * If the <code>src</code> and <code>dest</code> arguments refer to the
406 * same array object, then the copying is performed as if the
407 * components at positions <code>srcPos</code> through
408 * <code>srcPos+length-1</code> were first copied to a temporary
409 * array with <code>length</code> components and then the contents of
410 * the temporary array were copied into positions
411 * <code>destPos</code> through <code>destPos+length-1</code> of the
412 * destination array.
413 * <p>
414 * If <code>dest</code> is <code>null</code>, then a
415 * <code>NullPointerException</code> is thrown.
416 * <p>
417 * If <code>src</code> is <code>null</code>, then a
418 * <code>NullPointerException</code> is thrown and the destination
419 * array is not modified.
420 * <p>
421 * Otherwise, if any of the following is true, an
422 * <code>ArrayStoreException</code> is thrown and the destination is
423 * not modified:
424 * <ul>
425 * <li>The <code>src</code> argument refers to an object that is not an
426 * array.
427 * <li>The <code>dest</code> argument refers to an object that is not an
428 * array.
429 * <li>The <code>src</code> argument and <code>dest</code> argument refer
430 * to arrays whose component types are different primitive types.
431 * <li>The <code>src</code> argument refers to an array with a primitive
432 * component type and the <code>dest</code> argument refers to an array
433 * with a reference component type.
434 * <li>The <code>src</code> argument refers to an array with a reference
435 * component type and the <code>dest</code> argument refers to an array
436 * with a primitive component type.
437 * </ul>
438 * <p>
439 * Otherwise, if any of the following is true, an
440 * <code>IndexOutOfBoundsException</code> is
441 * thrown and the destination is not modified:
442 * <ul>
443 * <li>The <code>srcPos</code> argument is negative.
444 * <li>The <code>destPos</code> argument is negative.
445 * <li>The <code>length</code> argument is negative.
446 * <li><code>srcPos+length</code> is greater than
447 * <code>src.length</code>, the length of the source array.
448 * <li><code>destPos+length</code> is greater than
449 * <code>dest.length</code>, the length of the destination array.
450 * </ul>
451 * <p>
452 * Otherwise, if any actual component of the source array from
453 * position <code>srcPos</code> through
454 * <code>srcPos+length-1</code> cannot be converted to the component
455 * type of the destination array by assignment conversion, an
456 * <code>ArrayStoreException</code> is thrown. In this case, let
457 * <b><i>k</i></b> be the smallest nonnegative integer less than
458 * length such that <code>src[srcPos+</code><i>k</i><code>]</code>
459 * cannot be converted to the component type of the destination
460 * array; when the exception is thrown, source array components from
461 * positions <code>srcPos</code> through
462 * <code>srcPos+</code><i>k</i><code>-1</code>
463 * will already have been copied to destination array positions
464 * <code>destPos</code> through
465 * <code>destPos+</code><i>k</I><code>-1</code> and no other
466 * positions of the destination array will have been modified.
467 * (Because of the restrictions already itemized, this
468 * paragraph effectively applies only to the situation where both
469 * arrays have component types that are reference types.)
470 *
471 * @param src the source array.
472 * @param srcPos starting position in the source array.
473 * @param dest the destination array.
474 * @param destPos starting position in the destination data.
475 * @param length the number of array elements to be copied.
476 * @exception IndexOutOfBoundsException if copying would cause
477 * access of data outside array bounds.
478 * @exception ArrayStoreException if an element in the <code>src</code>
479 * array could not be stored into the <code>dest</code> array
480 * because of a type mismatch.
481 * @exception NullPointerException if either <code>src</code> or
482 * <code>dest</code> is <code>null</code>.
483 */
484 public static native void arraycopy(Object src, int srcPos,
485 Object dest, int destPos,
486 int length);
487
488 /**
489 * Returns the same hash code for the given object as
490 * would be returned by the default method hashCode(),
491 * whether or not the given object's class overrides
492 * hashCode().
493 * The hash code for the null reference is zero.
494 *
495 * @param x object for which the hashCode is to be calculated
496 * @return the hashCode
497 * @since JDK1.1
498 */
499 public static native int identityHashCode(Object x);
500
501 /**
502 * System properties. The following properties are guaranteed to be defined:
503 * <dl>
504 * <dt>java.version <dd>Java version number
505 * <dt>java.vendor <dd>Java vendor specific string
506 * <dt>java.vendor.url <dd>Java vendor URL
507 * <dt>java.home <dd>Java installation directory
508 * <dt>java.class.version <dd>Java class version number
509 * <dt>java.class.path <dd>Java classpath
510 * <dt>os.name <dd>Operating System Name
511 * <dt>os.arch <dd>Operating System Architecture
512 * <dt>os.version <dd>Operating System Version
513 * <dt>file.separator <dd>File separator ("/" on Unix)
514 * <dt>path.separator <dd>Path separator (":" on Unix)
515 * <dt>line.separator <dd>Line separator ("\n" on Unix)
516 * <dt>user.name <dd>User account name
517 * <dt>user.home <dd>User home directory
518 * <dt>user.dir <dd>User's current working directory
519 * </dl>
520 */
521
522 private static Properties props;
523 private static native Properties initProperties(Properties props);
524
525 /**
526 * Determines the current system properties.
527 * <p>
528 * First, if there is a security manager, its
529 * <code>checkPropertiesAccess</code> method is called with no
530 * arguments. This may result in a security exception.
531 * <p>
532 * The current set of system properties for use by the
533 * {@link #getProperty(String)} method is returned as a
534 * <code>Properties</code> object. If there is no current set of
535 * system properties, a set of system properties is first created and
536 * initialized. This set of system properties always includes values
537 * for the following keys:
538 * <table summary="Shows property keys and associated values">
539 * <tr><th>Key</th>
540 * <th>Description of Associated Value</th></tr>
541 * <tr><td><code>java.version</code></td>
542 * <td>Java Runtime Environment version</td></tr>
543 * <tr><td><code>java.vendor</code></td>
544 * <td>Java Runtime Environment vendor</td></tr
545 * <tr><td><code>java.vendor.url</code></td>
546 * <td>Java vendor URL</td></tr>
547 * <tr><td><code>java.home</code></td>
548 * <td>Java installation directory</td></tr>
549 * <tr><td><code>java.vm.specification.version</code></td>
550 * <td>Java Virtual Machine specification version</td></tr>
551 * <tr><td><code>java.vm.specification.vendor</code></td>
552 * <td>Java Virtual Machine specification vendor</td></tr>
553 * <tr><td><code>java.vm.specification.name</code></td>
554 * <td>Java Virtual Machine specification name</td></tr>
555 * <tr><td><code>java.vm.version</code></td>
556 * <td>Java Virtual Machine implementation version</td></tr>
557 * <tr><td><code>java.vm.vendor</code></td>
558 * <td>Java Virtual Machine implementation vendor</td></tr>
559 * <tr><td><code>java.vm.name</code></td>
560 * <td>Java Virtual Machine implementation name</td></tr>
561 * <tr><td><code>java.specification.version</code></td>
562 * <td>Java Runtime Environment specification version</td></tr>
563 * <tr><td><code>java.specification.vendor</code></td>
564 * <td>Java Runtime Environment specification vendor</td></tr>
565 * <tr><td><code>java.specification.name</code></td>
566 * <td>Java Runtime Environment specification name</td></tr>
567 * <tr><td><code>java.class.version</code></td>
568 * <td>Java class format version number</td></tr>
569 * <tr><td><code>java.class.path</code></td>
570 * <td>Java class path</td></tr>
571 * <tr><td><code>java.library.path</code></td>
572 * <td>List of paths to search when loading libraries</td></tr>
573 * <tr><td><code>java.io.tmpdir</code></td>
574 * <td>Default temp file path</td></tr>
575 * <tr><td><code>java.compiler</code></td>
576 * <td>Name of JIT compiler to use</td></tr>
577 * <tr><td><code>java.ext.dirs</code></td>
578 * <td>Path of extension directory or directories</td></tr>
579 * <tr><td><code>os.name</code></td>
580 * <td>Operating system name</td></tr>
581 * <tr><td><code>os.arch</code></td>
582 * <td>Operating system architecture</td></tr>
583 * <tr><td><code>os.version</code></td>
584 * <td>Operating system version</td></tr>
585 * <tr><td><code>file.separator</code></td>
586 * <td>File separator ("/" on UNIX)</td></tr>
587 * <tr><td><code>path.separator</code></td>
588 * <td>Path separator (":" on UNIX)</td></tr>
589 * <tr><td><code>line.separator</code></td>
590 * <td>Line separator ("\n" on UNIX)</td></tr>
591 * <tr><td><code>user.name</code></td>
592 * <td>User's account name</td></tr>
593 * <tr><td><code>user.home</code></td>
594 * <td>User's home directory</td></tr>
595 * <tr><td><code>user.dir</code></td>
596 * <td>User's current working directory</td></tr>
597 * </table>
598 * <p>
599 * Multiple paths in a system property value are separated by the path
600 * separator character of the platform.
601 * <p>
602 * Note that even if the security manager does not permit the
603 * <code>getProperties</code> operation, it may choose to permit the
604 * {@link #getProperty(String)} operation.
605 *
606 * @return the system properties
607 * @exception SecurityException if a security manager exists and its
608 * <code>checkPropertiesAccess</code> method doesn't allow access
609 * to the system properties.
610 * @see #setProperties
611 * @see java.lang.SecurityException
612 * @see java.lang.SecurityManager#checkPropertiesAccess()
613 * @see java.util.Properties
614 */
615 public static Properties getProperties() {
616 SecurityManager sm = getSecurityManager();
617 if (sm != null) {
618 sm.checkPropertiesAccess();
619 }
620
621 return props;
622 }
623
624 /**
625 * Sets the system properties to the <code>Properties</code>
626 * argument.
627 * <p>
628 * First, if there is a security manager, its
629 * <code>checkPropertiesAccess</code> method is called with no
630 * arguments. This may result in a security exception.
631 * <p>
632 * The argument becomes the current set of system properties for use
633 * by the {@link #getProperty(String)} method. If the argument is
634 * <code>null</code>, then the current set of system properties is
635 * forgotten.
636 *
637 * @param props the new system properties.
638 * @exception SecurityException if a security manager exists and its
639 * <code>checkPropertiesAccess</code> method doesn't allow access
640 * to the system properties.
641 * @see #getProperties
642 * @see java.util.Properties
643 * @see java.lang.SecurityException
644 * @see java.lang.SecurityManager#checkPropertiesAccess()
645 */
646 public static void setProperties(Properties props) {
647 SecurityManager sm = getSecurityManager();
648 if (sm != null) {
649 sm.checkPropertiesAccess();
650 }
651 if (props == null) {
652 props = new Properties();
653 initProperties(props);
654 }
655 System.props = props;
656 }
657
658 /**
659 * Gets the system property indicated by the specified key.
660 * <p>
661 * First, if there is a security manager, its
662 * <code>checkPropertyAccess</code> method is called with the key as
663 * its argument. This may result in a SecurityException.
664 * <p>
665 * If there is no current set of system properties, a set of system
666 * properties is first created and initialized in the same manner as
667 * for the <code>getProperties</code> method.
668 *
669 * @param key the name of the system property.
670 * @return the string value of the system property,
671 * or <code>null</code> if there is no property with that key.
672 *
673 * @exception SecurityException if a security manager exists and its
674 * <code>checkPropertyAccess</code> method doesn't allow
675 * access to the specified system property.
676 * @exception NullPointerException if <code>key</code> is
677 * <code>null</code>.
678 * @exception IllegalArgumentException if <code>key</code> is empty.
679 * @see #setProperty
680 * @see java.lang.SecurityException
681 * @see java.lang.SecurityManager#checkPropertyAccess(java.lang.String)
682 * @see java.lang.System#getProperties()
683 */
684 public static String getProperty(String key) {
685 checkKey(key);
686 SecurityManager sm = getSecurityManager();
687 if (sm != null) {
688 sm.checkPropertyAccess(key);
689 }
690
691 return props.getProperty(key);
692 }
693
694 /**
695 * Gets the system property indicated by the specified key.
696 * <p>
697 * First, if there is a security manager, its
698 * <code>checkPropertyAccess</code> method is called with the
699 * <code>key</code> as its argument.
700 * <p>
701 * If there is no current set of system properties, a set of system
702 * properties is first created and initialized in the same manner as
703 * for the <code>getProperties</code> method.
704 *
705 * @param key the name of the system property.
706 * @param def a default value.
707 * @return the string value of the system property,
708 * or the default value if there is no property with that key.
709 *
710 * @exception SecurityException if a security manager exists and its
711 * <code>checkPropertyAccess</code> method doesn't allow
712 * access to the specified system property.
713 * @exception NullPointerException if <code>key</code> is
714 * <code>null</code>.
715 * @exception IllegalArgumentException if <code>key</code> is empty.
716 * @see #setProperty
717 * @see java.lang.SecurityManager#checkPropertyAccess(java.lang.String)
718 * @see java.lang.System#getProperties()
719 */
720 public static String getProperty(String key, String def) {
721 checkKey(key);
722 SecurityManager sm = getSecurityManager();
723 if (sm != null) {
724 sm.checkPropertyAccess(key);
725 }
726
727 return props.getProperty(key, def);
728 }
729
730 /**
731 * Sets the system property indicated by the specified key.
732 * <p>
733 * First, if a security manager exists, its
734 * <code>SecurityManager.checkPermission</code> method
735 * is called with a <code>PropertyPermission(key, "write")</code>
736 * permission. This may result in a SecurityException being thrown.
737 * If no exception is thrown, the specified property is set to the given
738 * value.
739 * <p>
740 *
741 * @param key the name of the system property.
742 * @param value the value of the system property.
743 * @return the previous value of the system property,
744 * or <code>null</code> if it did not have one.
745 *
746 * @exception SecurityException if a security manager exists and its
747 * <code>checkPermission</code> method doesn't allow
748 * setting of the specified property.
749 * @exception NullPointerException if <code>key</code> or
750 * <code>value</code> is <code>null</code>.
751 * @exception IllegalArgumentException if <code>key</code> is empty.
752 * @see #getProperty
753 * @see java.lang.System#getProperty(java.lang.String)
754 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
755 * @see java.util.PropertyPermission
756 * @see SecurityManager#checkPermission
757 * @since 1.2
758 */
759 public static String setProperty(String key, String value) {
760 checkKey(key);
761 SecurityManager sm = getSecurityManager();
762 if (sm != null) {
763 sm.checkPermission(new PropertyPermission(key,
764 SecurityConstants.PROPERTY_WRITE_ACTION));
765 }
766
767 return (String) props.setProperty(key, value);
768 }
769
770 /**
771 * Removes the system property indicated by the specified key.
772 * <p>
773 * First, if a security manager exists, its
774 * <code>SecurityManager.checkPermission</code> method
775 * is called with a <code>PropertyPermission(key, "write")</code>
776 * permission. This may result in a SecurityException being thrown.
777 * If no exception is thrown, the specified property is removed.
778 * <p>
779 *
780 * @param key the name of the system property to be removed.
781 * @return the previous string value of the system property,
782 * or <code>null</code> if there was no property with that key.
783 *
784 * @exception SecurityException if a security manager exists and its
785 * <code>checkPropertyAccess</code> method doesn't allow
786 * access to the specified system property.
787 * @exception NullPointerException if <code>key</code> is
788 * <code>null</code>.
789 * @exception IllegalArgumentException if <code>key</code> is empty.
790 * @see #getProperty
791 * @see #setProperty
792 * @see java.util.Properties
793 * @see java.lang.SecurityException
794 * @see java.lang.SecurityManager#checkPropertiesAccess()
795 * @since 1.5
796 */
797 public static String clearProperty(String key) {
798 checkKey(key);
799 SecurityManager sm = getSecurityManager();
800 if (sm != null) {
801 sm.checkPermission(new PropertyPermission(key, "write"));
802 }
803
804 return (String) props.remove(key);
805 }
806
807 private static void checkKey(String key) {
808 if (key == null) {
809 throw new NullPointerException("key can't be null");
810 }
811 if (key.equals("")) {
812 throw new IllegalArgumentException("key can't be empty");
813 }
814 }
815
816 /**
817 * Gets the value of the specified environment variable. An
818 * environment variable is a system-dependent external named
819 * value.
820 *
821 * <p>If a security manager exists, its
822 * {@link SecurityManager#checkPermission checkPermission}
823 * method is called with a
824 * <code>{@link RuntimePermission}("getenv."+name)</code>
825 * permission. This may result in a {@link SecurityException}
826 * being thrown. If no exception is thrown the value of the
827 * variable <code>name</code> is returned.
828 *
829 * <p><a name="EnvironmentVSSystemProperties"><i>System
830 * properties</i> and <i>environment variables</i></a> are both
831 * conceptually mappings between names and values. Both
832 * mechanisms can be used to pass user-defined information to a
833 * Java process. Environment variables have a more global effect,
834 * because they are visible to all descendants of the process
835 * which defines them, not just the immediate Java subprocess.
836 * They can have subtly different semantics, such as case
837 * insensitivity, on different operating systems. For these
838 * reasons, environment variables are more likely to have
839 * unintended side effects. It is best to use system properties
840 * where possible. Environment variables should be used when a
841 * global effect is desired, or when an external system interface
842 * requires an environment variable (such as <code>PATH</code>).
843 *
844 * <p>On UNIX systems the alphabetic case of <code>name</code> is
845 * typically significant, while on Microsoft Windows systems it is
846 * typically not. For example, the expression
847 * <code>System.getenv("FOO").equals(System.getenv("foo"))</code>
848 * is likely to be true on Microsoft Windows.
849 *
850 * @param name the name of the environment variable
851 * @return the string value of the variable, or <code>null</code>
852 * if the variable is not defined in the system environment
853 * @throws NullPointerException if <code>name</code> is <code>null</code>
854 * @throws SecurityException
855 * if a security manager exists and its
856 * {@link SecurityManager#checkPermission checkPermission}
857 * method doesn't allow access to the environment variable
858 * <code>name</code>
859 * @see #getenv()
860 * @see ProcessBuilder#environment()
861 */
862 public static String getenv(String name) {
863 SecurityManager sm = getSecurityManager();
864 if (sm != null) {
865 sm.checkPermission(new RuntimePermission("getenv."+name));
866 }
867
868 return ProcessEnvironment.getenv(name);
869 }
870
871
872 /**
873 * Returns an unmodifiable string map view of the current system environment.
874 * The environment is a system-dependent mapping from names to
875 * values which is passed from parent to child processes.
876 *
877 * <p>If the system does not support environment variables, an
878 * empty map is returned.
879 *
880 * <p>The returned map will never contain null keys or values.
881 * Attempting to query the presence of a null key or value will
882 * throw a {@link NullPointerException}. Attempting to query
883 * the presence of a key or value which is not of type
884 * {@link String} will throw a {@link ClassCastException}.
885 *
886 * <p>The returned map and its collection views may not obey the
887 * general contract of the {@link Object#equals} and
888 * {@link Object#hashCode} methods.
889 *
890 * <p>The returned map is typically case-sensitive on all platforms.
891 *
892 * <p>If a security manager exists, its
893 * {@link SecurityManager#checkPermission checkPermission}
894 * method is called with a
895 * <code>{@link RuntimePermission}("getenv.*")</code>
896 * permission. This may result in a {@link SecurityException} being
897 * thrown.
898 *
899 * <p>When passing information to a Java subprocess,
900 * <a href=#EnvironmentVSSystemProperties>system properties</a>
901 * are generally preferred over environment variables.
902 *
903 * @return the environment as a map of variable names to values
904 * @throws SecurityException
905 * if a security manager exists and its
906 * {@link SecurityManager#checkPermission checkPermission}
907 * method doesn't allow access to the process environment
908 * @see #getenv(String)
909 * @see ProcessBuilder#environment()
910 * @since 1.5
911 */
912 public static java.util.Map<String,String> getenv() {
913 SecurityManager sm = getSecurityManager();
914 if (sm != null) {
915 sm.checkPermission(new RuntimePermission("getenv.*"));
916 }
917
918 return ProcessEnvironment.getenv();
919 }
920
921 /**
922 * Terminates the currently running Java Virtual Machine. The
923 * argument serves as a status code; by convention, a nonzero status
924 * code indicates abnormal termination.
925 * <p>
926 * This method calls the <code>exit</code> method in class
927 * <code>Runtime</code>. This method never returns normally.
928 * <p>
929 * The call <code>System.exit(n)</code> is effectively equivalent to
930 * the call:
931 * <blockquote><pre>
932 * Runtime.getRuntime().exit(n)
933 * </pre></blockquote>
934 *
935 * @param status exit status.
936 * @throws SecurityException
937 * if a security manager exists and its <code>checkExit</code>
938 * method doesn't allow exit with the specified status.
939 * @see java.lang.Runtime#exit(int)
940 */
941 public static void exit(int status) {
942 Runtime.getRuntime().exit(status);
943 }
944
945 /**
946 * Runs the garbage collector.
947 * <p>
948 * Calling the <code>gc</code> method suggests that the Java Virtual
949 * Machine expend effort toward recycling unused objects in order to
950 * make the memory they currently occupy available for quick reuse.
951 * When control returns from the method call, the Java Virtual
952 * Machine has made a best effort to reclaim space from all discarded
953 * objects.
954 * <p>
955 * The call <code>System.gc()</code> is effectively equivalent to the
956 * call:
957 * <blockquote><pre>
958 * Runtime.getRuntime().gc()
959 * </pre></blockquote>
960 *
961 * @see java.lang.Runtime#gc()
962 */
963 public static void gc() {
964 Runtime.getRuntime().gc();
965 }
966
967 /**
968 * Runs the finalization methods of any objects pending finalization.
969 * <p>
970 * Calling this method suggests that the Java Virtual Machine expend
971 * effort toward running the <code>finalize</code> methods of objects
972 * that have been found to be discarded but whose <code>finalize</code>
973 * methods have not yet been run. When control returns from the
974 * method call, the Java Virtual Machine has made a best effort to
975 * complete all outstanding finalizations.
976 * <p>
977 * The call <code>System.runFinalization()</code> is effectively
978 * equivalent to the call:
979 * <blockquote><pre>
980 * Runtime.getRuntime().runFinalization()
981 * </pre></blockquote>
982 *
983 * @see java.lang.Runtime#runFinalization()
984 */
985 public static void runFinalization() {
986 Runtime.getRuntime().runFinalization();
987 }
988
989 /**
990 * Enable or disable finalization on exit; doing so specifies that the
991 * finalizers of all objects that have finalizers that have not yet been
992 * automatically invoked are to be run before the Java runtime exits.
993 * By default, finalization on exit is disabled.
994 *
995 * <p>If there is a security manager,
996 * its <code>checkExit</code> method is first called
997 * with 0 as its argument to ensure the exit is allowed.
998 * This could result in a SecurityException.
999 *
1000 * @deprecated This method is inherently unsafe. It may result in
1001 * finalizers being called on live objects while other threads are
1002 * concurrently manipulating those objects, resulting in erratic
1003 * behavior or deadlock.
1004 * @param value indicating enabling or disabling of finalization
1005 * @throws SecurityException
1006 * if a security manager exists and its <code>checkExit</code>
1007 * method doesn't allow the exit.
1008 *
1009 * @see java.lang.Runtime#exit(int)
1010 * @see java.lang.Runtime#gc()
1011 * @see java.lang.SecurityManager#checkExit(int)
1012 * @since JDK1.1
1013 */
1014 @Deprecated
1015 public static void runFinalizersOnExit(boolean value) {
1016 Runtime.getRuntime().runFinalizersOnExit(value);
1017 }
1018
1019 /**
1020 * Loads a code file with the specified filename from the local file
1021 * system as a dynamic library. The filename
1022 * argument must be a complete path name.
1023 * <p>
1024 * The call <code>System.load(name)</code> is effectively equivalent
1025 * to the call:
1026 * <blockquote><pre>
1027 * Runtime.getRuntime().load(name)
1028 * </pre></blockquote>
1029 *
1030 * @param filename the file to load.
1031 * @exception SecurityException if a security manager exists and its
1032 * <code>checkLink</code> method doesn't allow
1033 * loading of the specified dynamic library
1034 * @exception UnsatisfiedLinkError if the file does not exist.
1035 * @exception NullPointerException if <code>filename</code> is
1036 * <code>null</code>
1037 * @see java.lang.Runtime#load(java.lang.String)
1038 * @see java.lang.SecurityManager#checkLink(java.lang.String)
1039 */
1040 public static void load(String filename) {
1041 Runtime.getRuntime().load0(getCallerClass(), filename);
1042 }
1043
1044 /**
1045 * Loads the system library specified by the <code>libname</code>
1046 * argument. The manner in which a library name is mapped to the
1047 * actual system library is system dependent.
1048 * <p>
1049 * The call <code>System.loadLibrary(name)</code> is effectively
1050 * equivalent to the call
1051 * <blockquote><pre>
1052 * Runtime.getRuntime().loadLibrary(name)
1053 * </pre></blockquote>
1054 *
1055 * @param libname the name of the library.
1056 * @exception SecurityException if a security manager exists and its
1057 * <code>checkLink</code> method doesn't allow
1058 * loading of the specified dynamic library
1059 * @exception UnsatisfiedLinkError if the library does not exist.
1060 * @exception NullPointerException if <code>libname</code> is
1061 * <code>null</code>
1062 * @see java.lang.Runtime#loadLibrary(java.lang.String)
1063 * @see java.lang.SecurityManager#checkLink(java.lang.String)
1064 */
1065 public static void loadLibrary(String libname) {
1066 Runtime.getRuntime().loadLibrary0(getCallerClass(), libname);
1067 }
1068
1069 /**
1070 * Maps a library name into a platform-specific string representing
1071 * a native library.
1072 *
1073 * @param libname the name of the library.
1074 * @return a platform-dependent native library name.
1075 * @exception NullPointerException if <code>libname</code> is
1076 * <code>null</code>
1077 * @see java.lang.System#loadLibrary(java.lang.String)
1078 * @see java.lang.ClassLoader#findLibrary(java.lang.String)
1079 * @since 1.2
1080 */
1081 public static native String mapLibraryName(String libname);
1082
1083 /**
1084 * The following two methods exist because in, out, and err must be
1085 * initialized to null. The compiler, however, cannot be permitted to
1086 * inline access to them, since they are later set to more sensible values
1087 * by initializeSystemClass().
1088 */
1089 private static InputStream nullInputStream() throws NullPointerException {
1090 if (currentTimeMillis() > 0) {
1091 return null;
1092 }
1093 throw new NullPointerException();
1094 }
1095
1096 private static PrintStream nullPrintStream() throws NullPointerException {
1097 if (currentTimeMillis() > 0) {
1098 return null;
1099 }
1100 throw new NullPointerException();
1101 }
1102
1103 /**
1104 * Initialize the system class. Called after thread initialization.
1105 */
1106 private static void initializeSystemClass() {
1107 props = new Properties();
1108 initProperties(props);
1109 sun.misc.Version.init();
1110 FileInputStream fdIn = new FileInputStream(FileDescriptor.in);
1111 FileOutputStream fdOut = new FileOutputStream(FileDescriptor.out);
1112 FileOutputStream fdErr = new FileOutputStream(FileDescriptor.err);
1113 setIn0(new BufferedInputStream(fdIn));
1114 setOut0(new PrintStream(new BufferedOutputStream(fdOut, 128), true));
1115 setErr0(new PrintStream(new BufferedOutputStream(fdErr, 128), true));
1116
1117 // Load the zip library now in order to keep java.util.zip.ZipFile
1118 // from trying to use itself to load this library later.
1119 loadLibrary("zip");
1120
1121 // Setup Java signal handlers for HUP, TERM, and INT (where available).
1122 Terminator.setup();
1123
1124 // Initialize any miscellenous operating system settings that need to be
1125 // set for the class libraries. Currently this is no-op everywhere except
1126 // for Windows where the process-wide error mode is set before the java.io
1127 // classes are used.
1128 sun.misc.VM.initializeOSEnvironment();
1129
1130 // Set the maximum amount of direct memory. This value is controlled
1131 // by the vm option -XX:MaxDirectMemorySize=<size>. This method acts
1132 // as an initializer only if it is called before sun.misc.VM.booted().
1133 sun.misc.VM.maxDirectMemory();
1134
1135 // Set a boolean to determine whether ClassLoader.loadClass accepts
1136 // array syntax. This value is controlled by the system property
1137 // "sun.lang.ClassLoader.allowArraySyntax". This method acts as
1138 // an initializer only if it is called before sun.misc.VM.booted().
1139 sun.misc.VM.allowArraySyntax();
1140
1141 // Subsystems that are invoked during initialization can invoke
1142 // sun.misc.VM.isBooted() in order to avoid doing things that should
1143 // wait until the application class loader has been set up.
1144 sun.misc.VM.booted();
1145
1146 // The main thread is not added to its thread group in the same
1147 // way as other threads; we must do it ourselves here.
1148 Thread current = Thread.currentThread();
1149 current.getThreadGroup().add(current);
1150
1151 // Allow privileged classes outside of java.lang
1152 sun.misc.SharedSecrets.setJavaLangAccess(new sun.misc.JavaLangAccess(){
1153 public sun.reflect.ConstantPool getConstantPool(Class klass) {
1154 return klass.getConstantPool();
1155 }
1156 public void setAnnotationType(Class klass, AnnotationType type) {
1157 klass.setAnnotationType(type);
1158 }
1159 public AnnotationType getAnnotationType(Class klass) {
1160 return klass.getAnnotationType();
1161 }
1162 public <E extends Enum<E>>
1163 E[] getEnumConstantsShared(Class<E> klass) {
1164 return klass.getEnumConstantsShared();
1165 }
1166 public void blockedOn(Thread t, Interruptible b) {
1167 t.blockedOn(b);
1168 }
1169 public void registerShutdownHook(int slot, Runnable r) {
1170 Shutdown.add(slot, r);
1171 }
1172 });
1173 }
1174
1175 /* returns the class of the caller. */
1176 static Class getCallerClass() {
1177 // NOTE use of more generic Reflection.getCallerClass()
1178 return Reflection.getCallerClass(3);
1179 }
1180 }