1 /*
2 * Copyright (c) 1994, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25 package java.lang;
26
27 import java.io.*;
28 import java.lang.reflect.Executable;
29 import java.lang.annotation.Annotation;
30 import java.security.AccessControlContext;
31 import java.util.Properties;
32 import java.util.PropertyPermission;
33 import java.util.StringTokenizer;
34 import java.util.Map;
35 import java.security.AccessController;
36 import java.security.PrivilegedAction;
37 import java.security.AllPermission;
38 import java.nio.channels.Channel;
39 import java.nio.channels.spi.SelectorProvider;
40 import sun.nio.ch.Interruptible;
41 import sun.reflect.CallerSensitive;
42 import sun.reflect.Reflection;
43 import sun.security.util.SecurityConstants;
44 import sun.reflect.annotation.AnnotationType;
45
46 /**
47 * The <code>System</code> class contains several useful class fields
48 * and methods. It cannot be instantiated.
49 *
50 * <p>Among the facilities provided by the <code>System</code> class
51 * are standard input, standard output, and error output streams;
52 * access to externally defined properties and environment
53 * variables; a means of loading files and libraries; and a utility
54 * method for quickly copying a portion of an array.
55 *
56 * @author unascribed
57 * @since JDK1.0
58 */
59 public final class System {
60
61 /* register the natives via the static initializer.
62 *
63 * VM will invoke the initializeSystemClass method to complete
64 * the initialization for this class separated from clinit.
65 * Note that to use properties set by the VM, see the constraints
66 * described in the initializeSystemClass method.
67 */
68 private static native void registerNatives();
69 static {
70 registerNatives();
71 }
72
73 /** Don't let anyone instantiate this class */
74 private System() {
75 }
76
77 /**
78 * The "standard" input stream. This stream is already
79 * open and ready to supply input data. Typically this stream
80 * corresponds to keyboard input or another input source specified by
81 * the host environment or user.
82 */
83 public final static InputStream in = null;
84
85 /**
86 * The "standard" output stream. This stream is already
87 * open and ready to accept output data. Typically this stream
88 * corresponds to display output or another output destination
89 * specified by the host environment or user.
90 * <p>
91 * For simple stand-alone Java applications, a typical way to write
92 * a line of output data is:
93 * <blockquote><pre>
94 * System.out.println(data)
95 * </pre></blockquote>
96 * <p>
97 * See the <code>println</code> methods in class <code>PrintStream</code>.
98 *
99 * @see java.io.PrintStream#println()
100 * @see java.io.PrintStream#println(boolean)
101 * @see java.io.PrintStream#println(char)
102 * @see java.io.PrintStream#println(char[])
103 * @see java.io.PrintStream#println(double)
104 * @see java.io.PrintStream#println(float)
105 * @see java.io.PrintStream#println(int)
106 * @see java.io.PrintStream#println(long)
107 * @see java.io.PrintStream#println(java.lang.Object)
108 * @see java.io.PrintStream#println(java.lang.String)
109 */
110 public final static PrintStream out = null;
111
112 /**
113 * The "standard" error output stream. This stream is already
114 * open and ready to accept output data.
115 * <p>
116 * Typically this stream corresponds to display output or another
117 * output destination specified by the host environment or user. By
118 * convention, this output stream is used to display error messages
119 * or other information that should come to the immediate attention
120 * of a user even if the principal output stream, the value of the
121 * variable <code>out</code>, has been redirected to a file or other
122 * destination that is typically not continuously monitored.
123 */
124 public final static PrintStream err = null;
125
126 /* The security manager for the system.
127 */
128 private static volatile SecurityManager security = null;
129
130 /**
131 * Reassigns the "standard" input stream.
132 *
133 * <p>First, if there is a security manager, its <code>checkPermission</code>
134 * method is called with a <code>RuntimePermission("setIO")</code> permission
135 * to see if it's ok to reassign the "standard" input stream.
136 * <p>
137 *
138 * @param in the new standard input stream.
139 *
140 * @throws SecurityException
141 * if a security manager exists and its
142 * <code>checkPermission</code> method doesn't allow
143 * reassigning of the standard input stream.
144 *
145 * @see SecurityManager#checkPermission
146 * @see java.lang.RuntimePermission
147 *
148 * @since JDK1.1
149 */
150 public static void setIn(InputStream in) {
151 checkIO();
152 setIn0(in);
153 }
154
155 /**
156 * Reassigns the "standard" output stream.
157 *
158 * <p>First, if there is a security manager, its <code>checkPermission</code>
159 * method is called with a <code>RuntimePermission("setIO")</code> permission
160 * to see if it's ok to reassign the "standard" output stream.
161 *
162 * @param out the new standard output stream
163 *
164 * @throws SecurityException
165 * if a security manager exists and its
166 * <code>checkPermission</code> method doesn't allow
167 * reassigning of the standard output stream.
168 *
169 * @see SecurityManager#checkPermission
170 * @see java.lang.RuntimePermission
171 *
172 * @since JDK1.1
173 */
174 public static void setOut(PrintStream out) {
175 checkIO();
176 setOut0(out);
177 }
178
179 /**
180 * Reassigns the "standard" error output stream.
181 *
182 * <p>First, if there is a security manager, its <code>checkPermission</code>
183 * method is called with a <code>RuntimePermission("setIO")</code> permission
184 * to see if it's ok to reassign the "standard" error output stream.
185 *
186 * @param err the new standard error output stream.
187 *
188 * @throws SecurityException
189 * if a security manager exists and its
190 * <code>checkPermission</code> method doesn't allow
191 * reassigning of the standard error output stream.
192 *
193 * @see SecurityManager#checkPermission
194 * @see java.lang.RuntimePermission
195 *
196 * @since JDK1.1
197 */
198 public static void setErr(PrintStream err) {
199 checkIO();
200 setErr0(err);
201 }
202
203 private static volatile Console cons = null;
204 /**
205 * Returns the unique {@link java.io.Console Console} object associated
206 * with the current Java virtual machine, if any.
207 *
208 * @return The system console, if any, otherwise <tt>null</tt>.
209 *
210 * @since 1.6
211 */
212 public static Console console() {
213 if (cons == null) {
214 synchronized (System.class) {
215 cons = sun.misc.SharedSecrets.getJavaIOAccess().console();
216 }
217 }
218 return cons;
219 }
220
221 /**
222 * Returns the channel inherited from the entity that created this
223 * Java virtual machine.
224 *
225 * <p> This method returns the channel obtained by invoking the
226 * {@link java.nio.channels.spi.SelectorProvider#inheritedChannel
227 * inheritedChannel} method of the system-wide default
228 * {@link java.nio.channels.spi.SelectorProvider} object. </p>
229 *
230 * <p> In addition to the network-oriented channels described in
231 * {@link java.nio.channels.spi.SelectorProvider#inheritedChannel
232 * inheritedChannel}, this method may return other kinds of
233 * channels in the future.
234 *
235 * @return The inherited channel, if any, otherwise <tt>null</tt>.
236 *
237 * @throws IOException
238 * If an I/O error occurs
239 *
240 * @throws SecurityException
241 * If a security manager is present and it does not
242 * permit access to the channel.
243 *
244 * @since 1.5
245 */
246 public static Channel inheritedChannel() throws IOException {
247 return SelectorProvider.provider().inheritedChannel();
248 }
249
250 private static void checkIO() {
251 SecurityManager sm = getSecurityManager();
252 if (sm != null) {
253 sm.checkPermission(new RuntimePermission("setIO"));
254 }
255 }
256
257 private static native void setIn0(InputStream in);
258 private static native void setOut0(PrintStream out);
259 private static native void setErr0(PrintStream err);
260
261 /**
262 * Sets the System security.
263 *
264 * <p> If there is a security manager already installed, this method first
265 * calls the security manager's <code>checkPermission</code> method
266 * with a <code>RuntimePermission("setSecurityManager")</code>
267 * permission to ensure it's ok to replace the existing
268 * security manager.
269 * This may result in throwing a <code>SecurityException</code>.
270 *
271 * <p> Otherwise, the argument is established as the current
272 * security manager. If the argument is <code>null</code> and no
273 * security manager has been established, then no action is taken and
274 * the method simply returns.
275 *
276 * @param s the security manager.
277 * @exception SecurityException if the security manager has already
278 * been set and its <code>checkPermission</code> method
279 * doesn't allow it to be replaced.
280 * @see #getSecurityManager
281 * @see SecurityManager#checkPermission
282 * @see java.lang.RuntimePermission
283 */
284 public static
285 void setSecurityManager(final SecurityManager s) {
286 try {
287 s.checkPackageAccess("java.lang");
288 } catch (Exception e) {
289 // no-op
290 }
291 setSecurityManager0(s);
292 }
293
294 private static synchronized
295 void setSecurityManager0(final SecurityManager s) {
296 SecurityManager sm = getSecurityManager();
297 if (sm != null) {
298 // ask the currently installed security manager if we
299 // can replace it.
300 sm.checkPermission(new RuntimePermission
301 ("setSecurityManager"));
302 }
303
304 if ((s != null) && (s.getClass().getClassLoader() != null)) {
305 // New security manager class is not on bootstrap classpath.
306 // Cause policy to get initialized before we install the new
307 // security manager, in order to prevent infinite loops when
308 // trying to initialize the policy (which usually involves
309 // accessing some security and/or system properties, which in turn
310 // calls the installed security manager's checkPermission method
311 // which will loop infinitely if there is a non-system class
312 // (in this case: the new security manager class) on the stack).
313 AccessController.doPrivileged(new PrivilegedAction<Object>() {
314 public Object run() {
315 s.getClass().getProtectionDomain().implies
316 (SecurityConstants.ALL_PERMISSION);
317 return null;
318 }
319 });
320 }
321
322 security = s;
323 }
324
325 /**
326 * Gets the system security interface.
327 *
328 * @return if a security manager has already been established for the
329 * current application, then that security manager is returned;
330 * otherwise, <code>null</code> is returned.
331 * @see #setSecurityManager
332 */
333 public static SecurityManager getSecurityManager() {
334 return security;
335 }
336
337 /**
338 * Returns the current time in milliseconds. Note that
339 * while the unit of time of the return value is a millisecond,
340 * the granularity of the value depends on the underlying
341 * operating system and may be larger. For example, many
342 * operating systems measure time in units of tens of
343 * milliseconds.
344 *
345 * <p> See the description of the class <code>Date</code> for
346 * a discussion of slight discrepancies that may arise between
347 * "computer time" and coordinated universal time (UTC).
348 *
349 * @return the difference, measured in milliseconds, between
350 * the current time and midnight, January 1, 1970 UTC.
351 * @see java.util.Date
352 */
353 public static native long currentTimeMillis();
354
355 /**
356 * Returns the current value of the running Java Virtual Machine's
357 * high-resolution time source, in nanoseconds.
358 *
359 * <p>This method can only be used to measure elapsed time and is
360 * not related to any other notion of system or wall-clock time.
361 * The value returned represents nanoseconds since some fixed but
362 * arbitrary <i>origin</i> time (perhaps in the future, so values
363 * may be negative). The same origin is used by all invocations of
364 * this method in an instance of a Java virtual machine; other
365 * virtual machine instances are likely to use a different origin.
366 *
367 * <p>This method provides nanosecond precision, but not necessarily
368 * nanosecond resolution (that is, how frequently the value changes)
369 * - no guarantees are made except that the resolution is at least as
370 * good as that of {@link #currentTimeMillis()}.
371 *
372 * <p>Differences in successive calls that span greater than
373 * approximately 292 years (2<sup>63</sup> nanoseconds) will not
374 * correctly compute elapsed time due to numerical overflow.
375 *
376 * <p>The values returned by this method become meaningful only when
377 * the difference between two such values, obtained within the same
378 * instance of a Java virtual machine, is computed.
379 *
380 * <p> For example, to measure how long some code takes to execute:
381 * <pre> {@code
382 * long startTime = System.nanoTime();
383 * // ... the code being measured ...
384 * long estimatedTime = System.nanoTime() - startTime;}</pre>
385 *
386 * <p>To compare two nanoTime values
387 * <pre> {@code
388 * long t0 = System.nanoTime();
389 * ...
390 * long t1 = System.nanoTime();}</pre>
391 *
392 * one should use {@code t1 - t0 < 0}, not {@code t1 < t0},
393 * because of the possibility of numerical overflow.
394 *
395 * @return the current value of the running Java Virtual Machine's
396 * high-resolution time source, in nanoseconds
397 * @since 1.5
398 */
399 public static native long nanoTime();
400
401 /**
402 * Copies an array from the specified source array, beginning at the
403 * specified position, to the specified position of the destination array.
404 * A subsequence of array components are copied from the source
405 * array referenced by <code>src</code> to the destination array
406 * referenced by <code>dest</code>. The number of components copied is
407 * equal to the <code>length</code> argument. The components at
408 * positions <code>srcPos</code> through
409 * <code>srcPos+length-1</code> in the source array are copied into
410 * positions <code>destPos</code> through
411 * <code>destPos+length-1</code>, respectively, of the destination
412 * array.
413 * <p>
414 * If the <code>src</code> and <code>dest</code> arguments refer to the
415 * same array object, then the copying is performed as if the
416 * components at positions <code>srcPos</code> through
417 * <code>srcPos+length-1</code> were first copied to a temporary
418 * array with <code>length</code> components and then the contents of
419 * the temporary array were copied into positions
420 * <code>destPos</code> through <code>destPos+length-1</code> of the
421 * destination array.
422 * <p>
423 * If <code>dest</code> is <code>null</code>, then a
424 * <code>NullPointerException</code> is thrown.
425 * <p>
426 * If <code>src</code> is <code>null</code>, then a
427 * <code>NullPointerException</code> is thrown and the destination
428 * array is not modified.
429 * <p>
430 * Otherwise, if any of the following is true, an
431 * <code>ArrayStoreException</code> is thrown and the destination is
432 * not modified:
433 * <ul>
434 * <li>The <code>src</code> argument refers to an object that is not an
435 * array.
436 * <li>The <code>dest</code> argument refers to an object that is not an
437 * array.
438 * <li>The <code>src</code> argument and <code>dest</code> argument refer
439 * to arrays whose component types are different primitive types.
440 * <li>The <code>src</code> argument refers to an array with a primitive
441 * component type and the <code>dest</code> argument refers to an array
442 * with a reference component type.
443 * <li>The <code>src</code> argument refers to an array with a reference
444 * component type and the <code>dest</code> argument refers to an array
445 * with a primitive component type.
446 * </ul>
447 * <p>
448 * Otherwise, if any of the following is true, an
449 * <code>IndexOutOfBoundsException</code> is
450 * thrown and the destination is not modified:
451 * <ul>
452 * <li>The <code>srcPos</code> argument is negative.
453 * <li>The <code>destPos</code> argument is negative.
454 * <li>The <code>length</code> argument is negative.
455 * <li><code>srcPos+length</code> is greater than
456 * <code>src.length</code>, the length of the source array.
457 * <li><code>destPos+length</code> is greater than
458 * <code>dest.length</code>, the length of the destination array.
459 * </ul>
460 * <p>
461 * Otherwise, if any actual component of the source array from
462 * position <code>srcPos</code> through
463 * <code>srcPos+length-1</code> cannot be converted to the component
464 * type of the destination array by assignment conversion, an
465 * <code>ArrayStoreException</code> is thrown. In this case, let
466 * <b><i>k</i></b> be the smallest nonnegative integer less than
467 * length such that <code>src[srcPos+</code><i>k</i><code>]</code>
468 * cannot be converted to the component type of the destination
469 * array; when the exception is thrown, source array components from
470 * positions <code>srcPos</code> through
471 * <code>srcPos+</code><i>k</i><code>-1</code>
472 * will already have been copied to destination array positions
473 * <code>destPos</code> through
474 * <code>destPos+</code><i>k</I><code>-1</code> and no other
475 * positions of the destination array will have been modified.
476 * (Because of the restrictions already itemized, this
477 * paragraph effectively applies only to the situation where both
478 * arrays have component types that are reference types.)
479 *
480 * @param src the source array.
481 * @param srcPos starting position in the source array.
482 * @param dest the destination array.
483 * @param destPos starting position in the destination data.
484 * @param length the number of array elements to be copied.
485 * @exception IndexOutOfBoundsException if copying would cause
486 * access of data outside array bounds.
487 * @exception ArrayStoreException if an element in the <code>src</code>
488 * array could not be stored into the <code>dest</code> array
489 * because of a type mismatch.
490 * @exception NullPointerException if either <code>src</code> or
491 * <code>dest</code> is <code>null</code>.
492 */
493 public static native void arraycopy(Object src, int srcPos,
494 Object dest, int destPos,
495 int length);
496
497 /**
498 * Returns the same hash code for the given object as
499 * would be returned by the default method hashCode(),
500 * whether or not the given object's class overrides
501 * hashCode().
502 * The hash code for the null reference is zero.
503 *
504 * @param x object for which the hashCode is to be calculated
505 * @return the hashCode
506 * @since JDK1.1
507 */
508 public static native int identityHashCode(Object x);
509
510 /**
511 * System properties. The following properties are guaranteed to be defined:
512 * <dl>
513 * <dt>java.version <dd>Java version number
514 * <dt>java.vendor <dd>Java vendor specific string
515 * <dt>java.vendor.url <dd>Java vendor URL
516 * <dt>java.home <dd>Java installation directory
517 * <dt>java.class.version <dd>Java class version number
518 * <dt>java.class.path <dd>Java classpath
519 * <dt>os.name <dd>Operating System Name
520 * <dt>os.arch <dd>Operating System Architecture
521 * <dt>os.version <dd>Operating System Version
522 * <dt>file.separator <dd>File separator ("/" on Unix)
523 * <dt>path.separator <dd>Path separator (":" on Unix)
524 * <dt>line.separator <dd>Line separator ("\n" on Unix)
525 * <dt>user.name <dd>User account name
526 * <dt>user.home <dd>User home directory
527 * <dt>user.dir <dd>User's current working directory
528 * </dl>
529 */
530
531 private static Properties props;
532 private static native Properties initProperties(Properties props);
533
534 /**
535 * Determines the current system properties.
536 * <p>
537 * First, if there is a security manager, its
538 * <code>checkPropertiesAccess</code> method is called with no
539 * arguments. This may result in a security exception.
540 * <p>
541 * The current set of system properties for use by the
542 * {@link #getProperty(String)} method is returned as a
543 * <code>Properties</code> object. If there is no current set of
544 * system properties, a set of system properties is first created and
545 * initialized. This set of system properties always includes values
546 * for the following keys:
547 * <table summary="Shows property keys and associated values">
548 * <tr><th>Key</th>
549 * <th>Description of Associated Value</th></tr>
550 * <tr><td><code>java.version</code></td>
551 * <td>Java Runtime Environment version</td></tr>
552 * <tr><td><code>java.vendor</code></td>
553 * <td>Java Runtime Environment vendor</td></tr>
554 * <tr><td><code>java.vendor.url</code></td>
555 * <td>Java vendor URL</td></tr>
556 * <tr><td><code>java.home</code></td>
557 * <td>Java installation directory</td></tr>
558 * <tr><td><code>java.vm.specification.version</code></td>
559 * <td>Java Virtual Machine specification version</td></tr>
560 * <tr><td><code>java.vm.specification.vendor</code></td>
561 * <td>Java Virtual Machine specification vendor</td></tr>
562 * <tr><td><code>java.vm.specification.name</code></td>
563 * <td>Java Virtual Machine specification name</td></tr>
564 * <tr><td><code>java.vm.version</code></td>
565 * <td>Java Virtual Machine implementation version</td></tr>
566 * <tr><td><code>java.vm.vendor</code></td>
567 * <td>Java Virtual Machine implementation vendor</td></tr>
568 * <tr><td><code>java.vm.name</code></td>
569 * <td>Java Virtual Machine implementation name</td></tr>
570 * <tr><td><code>java.specification.version</code></td>
571 * <td>Java Runtime Environment specification version</td></tr>
572 * <tr><td><code>java.specification.vendor</code></td>
573 * <td>Java Runtime Environment specification vendor</td></tr>
574 * <tr><td><code>java.specification.name</code></td>
575 * <td>Java Runtime Environment specification name</td></tr>
576 * <tr><td><code>java.class.version</code></td>
577 * <td>Java class format version number</td></tr>
578 * <tr><td><code>java.class.path</code></td>
579 * <td>Java class path</td></tr>
580 * <tr><td><code>java.library.path</code></td>
581 * <td>List of paths to search when loading libraries</td></tr>
582 * <tr><td><code>java.io.tmpdir</code></td>
583 * <td>Default temp file path</td></tr>
584 * <tr><td><code>java.compiler</code></td>
585 * <td>Name of JIT compiler to use</td></tr>
586 * <tr><td><code>java.ext.dirs</code></td>
587 * <td>Path of extension directory or directories
588 * <b>Deprecated.</b> <i>This property, and the mechanism
589 * which implements it, may be removed in a future
590 * release.</i> </td></tr>
591 * <tr><td><code>os.name</code></td>
592 * <td>Operating system name</td></tr>
593 * <tr><td><code>os.arch</code></td>
594 * <td>Operating system architecture</td></tr>
595 * <tr><td><code>os.version</code></td>
596 * <td>Operating system version</td></tr>
597 * <tr><td><code>file.separator</code></td>
598 * <td>File separator ("/" on UNIX)</td></tr>
599 * <tr><td><code>path.separator</code></td>
600 * <td>Path separator (":" on UNIX)</td></tr>
601 * <tr><td><code>line.separator</code></td>
602 * <td>Line separator ("\n" on UNIX)</td></tr>
603 * <tr><td><code>user.name</code></td>
604 * <td>User's account name</td></tr>
605 * <tr><td><code>user.home</code></td>
606 * <td>User's home directory</td></tr>
607 * <tr><td><code>user.dir</code></td>
608 * <td>User's current working directory</td></tr>
609 * </table>
610 * <p>
611 * Multiple paths in a system property value are separated by the path
612 * separator character of the platform.
613 * <p>
614 * Note that even if the security manager does not permit the
615 * <code>getProperties</code> operation, it may choose to permit the
616 * {@link #getProperty(String)} operation.
617 *
618 * @return the system properties
619 * @exception SecurityException if a security manager exists and its
620 * <code>checkPropertiesAccess</code> method doesn't allow access
621 * to the system properties.
622 * @see #setProperties
623 * @see java.lang.SecurityException
624 * @see java.lang.SecurityManager#checkPropertiesAccess()
625 * @see java.util.Properties
626 */
627 public static Properties getProperties() {
628 SecurityManager sm = getSecurityManager();
629 if (sm != null) {
630 sm.checkPropertiesAccess();
631 }
632
633 return props;
634 }
635
636 /**
637 * Returns the system-dependent line separator string. It always
638 * returns the same value - the initial value of the {@linkplain
639 * #getProperty(String) system property} {@code line.separator}.
640 *
641 * <p>On UNIX systems, it returns {@code "\n"}; on Microsoft
642 * Windows systems it returns {@code "\r\n"}.
643 *
644 * @return the system-dependent line separator string
645 * @since 1.7
646 */
647 public static String lineSeparator() {
648 return lineSeparator;
649 }
650
651 private static String lineSeparator;
652
653 /**
654 * Sets the system properties to the <code>Properties</code>
655 * argument.
656 * <p>
657 * First, if there is a security manager, its
658 * <code>checkPropertiesAccess</code> method is called with no
659 * arguments. This may result in a security exception.
660 * <p>
661 * The argument becomes the current set of system properties for use
662 * by the {@link #getProperty(String)} method. If the argument is
663 * <code>null</code>, then the current set of system properties is
664 * forgotten.
665 *
666 * @param props the new system properties.
667 * @exception SecurityException if a security manager exists and its
668 * <code>checkPropertiesAccess</code> method doesn't allow access
669 * to the system properties.
670 * @see #getProperties
671 * @see java.util.Properties
672 * @see java.lang.SecurityException
673 * @see java.lang.SecurityManager#checkPropertiesAccess()
674 */
675 public static void setProperties(Properties props) {
676 SecurityManager sm = getSecurityManager();
677 if (sm != null) {
678 sm.checkPropertiesAccess();
679 }
680 if (props == null) {
681 props = new Properties();
682 initProperties(props);
683 }
684 System.props = props;
685 }
686
687 /**
688 * Gets the system property indicated by the specified key.
689 * <p>
690 * First, if there is a security manager, its
691 * <code>checkPropertyAccess</code> method is called with the key as
692 * its argument. This may result in a SecurityException.
693 * <p>
694 * If there is no current set of system properties, a set of system
695 * properties is first created and initialized in the same manner as
696 * for the <code>getProperties</code> method.
697 *
698 * @param key the name of the system property.
699 * @return the string value of the system property,
700 * or <code>null</code> if there is no property with that key.
701 *
702 * @exception SecurityException if a security manager exists and its
703 * <code>checkPropertyAccess</code> method doesn't allow
704 * access to the specified system property.
705 * @exception NullPointerException if <code>key</code> is
706 * <code>null</code>.
707 * @exception IllegalArgumentException if <code>key</code> is empty.
708 * @see #setProperty
709 * @see java.lang.SecurityException
710 * @see java.lang.SecurityManager#checkPropertyAccess(java.lang.String)
711 * @see java.lang.System#getProperties()
712 */
713 public static String getProperty(String key) {
714 checkKey(key);
715 SecurityManager sm = getSecurityManager();
716 if (sm != null) {
717 sm.checkPropertyAccess(key);
718 }
719
720 return props.getProperty(key);
721 }
722
723 /**
724 * Gets the system property indicated by the specified key.
725 * <p>
726 * First, if there is a security manager, its
727 * <code>checkPropertyAccess</code> method is called with the
728 * <code>key</code> as its argument.
729 * <p>
730 * If there is no current set of system properties, a set of system
731 * properties is first created and initialized in the same manner as
732 * for the <code>getProperties</code> method.
733 *
734 * @param key the name of the system property.
735 * @param def a default value.
736 * @return the string value of the system property,
737 * or the default value if there is no property with that key.
738 *
739 * @exception SecurityException if a security manager exists and its
740 * <code>checkPropertyAccess</code> method doesn't allow
741 * access to the specified system property.
742 * @exception NullPointerException if <code>key</code> is
743 * <code>null</code>.
744 * @exception IllegalArgumentException if <code>key</code> is empty.
745 * @see #setProperty
746 * @see java.lang.SecurityManager#checkPropertyAccess(java.lang.String)
747 * @see java.lang.System#getProperties()
748 */
749 public static String getProperty(String key, String def) {
750 checkKey(key);
751 SecurityManager sm = getSecurityManager();
752 if (sm != null) {
753 sm.checkPropertyAccess(key);
754 }
755
756 return props.getProperty(key, def);
757 }
758
759 /**
760 * Sets the system property indicated by the specified key.
761 * <p>
762 * First, if a security manager exists, its
763 * <code>SecurityManager.checkPermission</code> method
764 * is called with a <code>PropertyPermission(key, "write")</code>
765 * permission. This may result in a SecurityException being thrown.
766 * If no exception is thrown, the specified property is set to the given
767 * value.
768 * <p>
769 *
770 * @param key the name of the system property.
771 * @param value the value of the system property.
772 * @return the previous value of the system property,
773 * or <code>null</code> if it did not have one.
774 *
775 * @exception SecurityException if a security manager exists and its
776 * <code>checkPermission</code> method doesn't allow
777 * setting of the specified property.
778 * @exception NullPointerException if <code>key</code> or
779 * <code>value</code> is <code>null</code>.
780 * @exception IllegalArgumentException if <code>key</code> is empty.
781 * @see #getProperty
782 * @see java.lang.System#getProperty(java.lang.String)
783 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
784 * @see java.util.PropertyPermission
785 * @see SecurityManager#checkPermission
786 * @since 1.2
787 */
788 public static String setProperty(String key, String value) {
789 checkKey(key);
790 SecurityManager sm = getSecurityManager();
791 if (sm != null) {
792 sm.checkPermission(new PropertyPermission(key,
793 SecurityConstants.PROPERTY_WRITE_ACTION));
794 }
795
796 return (String) props.setProperty(key, value);
797 }
798
799 /**
800 * Removes the system property indicated by the specified key.
801 * <p>
802 * First, if a security manager exists, its
803 * <code>SecurityManager.checkPermission</code> method
804 * is called with a <code>PropertyPermission(key, "write")</code>
805 * permission. This may result in a SecurityException being thrown.
806 * If no exception is thrown, the specified property is removed.
807 * <p>
808 *
809 * @param key the name of the system property to be removed.
810 * @return the previous string value of the system property,
811 * or <code>null</code> if there was no property with that key.
812 *
813 * @exception SecurityException if a security manager exists and its
814 * <code>checkPropertyAccess</code> method doesn't allow
815 * access to the specified system property.
816 * @exception NullPointerException if <code>key</code> is
817 * <code>null</code>.
818 * @exception IllegalArgumentException if <code>key</code> is empty.
819 * @see #getProperty
820 * @see #setProperty
821 * @see java.util.Properties
822 * @see java.lang.SecurityException
823 * @see java.lang.SecurityManager#checkPropertiesAccess()
824 * @since 1.5
825 */
826 public static String clearProperty(String key) {
827 checkKey(key);
828 SecurityManager sm = getSecurityManager();
829 if (sm != null) {
830 sm.checkPermission(new PropertyPermission(key, "write"));
831 }
832
833 return (String) props.remove(key);
834 }
835
836 private static void checkKey(String key) {
837 if (key == null) {
838 throw new NullPointerException("key can't be null");
839 }
840 if (key.equals("")) {
841 throw new IllegalArgumentException("key can't be empty");
842 }
843 }
844
845 /**
846 * Gets the value of the specified environment variable. An
847 * environment variable is a system-dependent external named
848 * value.
849 *
850 * <p>If a security manager exists, its
851 * {@link SecurityManager#checkPermission checkPermission}
852 * method is called with a
853 * <code>{@link RuntimePermission}("getenv."+name)</code>
854 * permission. This may result in a {@link SecurityException}
855 * being thrown. If no exception is thrown the value of the
856 * variable <code>name</code> is returned.
857 *
858 * <p><a name="EnvironmentVSSystemProperties"><i>System
859 * properties</i> and <i>environment variables</i></a> are both
860 * conceptually mappings between names and values. Both
861 * mechanisms can be used to pass user-defined information to a
862 * Java process. Environment variables have a more global effect,
863 * because they are visible to all descendants of the process
864 * which defines them, not just the immediate Java subprocess.
865 * They can have subtly different semantics, such as case
866 * insensitivity, on different operating systems. For these
867 * reasons, environment variables are more likely to have
868 * unintended side effects. It is best to use system properties
869 * where possible. Environment variables should be used when a
870 * global effect is desired, or when an external system interface
871 * requires an environment variable (such as <code>PATH</code>).
872 *
873 * <p>On UNIX systems the alphabetic case of <code>name</code> is
874 * typically significant, while on Microsoft Windows systems it is
875 * typically not. For example, the expression
876 * <code>System.getenv("FOO").equals(System.getenv("foo"))</code>
877 * is likely to be true on Microsoft Windows.
878 *
879 * @param name the name of the environment variable
880 * @return the string value of the variable, or <code>null</code>
881 * if the variable is not defined in the system environment
882 * @throws NullPointerException if <code>name</code> is <code>null</code>
883 * @throws SecurityException
884 * if a security manager exists and its
885 * {@link SecurityManager#checkPermission checkPermission}
886 * method doesn't allow access to the environment variable
887 * <code>name</code>
888 * @see #getenv()
889 * @see ProcessBuilder#environment()
890 */
891 public static String getenv(String name) {
892 SecurityManager sm = getSecurityManager();
893 if (sm != null) {
894 sm.checkPermission(new RuntimePermission("getenv."+name));
895 }
896
897 return ProcessEnvironment.getenv(name);
898 }
899
900
901 /**
902 * Returns an unmodifiable string map view of the current system environment.
903 * The environment is a system-dependent mapping from names to
904 * values which is passed from parent to child processes.
905 *
906 * <p>If the system does not support environment variables, an
907 * empty map is returned.
908 *
909 * <p>The returned map will never contain null keys or values.
910 * Attempting to query the presence of a null key or value will
911 * throw a {@link NullPointerException}. Attempting to query
912 * the presence of a key or value which is not of type
913 * {@link String} will throw a {@link ClassCastException}.
914 *
915 * <p>The returned map and its collection views may not obey the
916 * general contract of the {@link Object#equals} and
917 * {@link Object#hashCode} methods.
918 *
919 * <p>The returned map is typically case-sensitive on all platforms.
920 *
921 * <p>If a security manager exists, its
922 * {@link SecurityManager#checkPermission checkPermission}
923 * method is called with a
924 * <code>{@link RuntimePermission}("getenv.*")</code>
925 * permission. This may result in a {@link SecurityException} being
926 * thrown.
927 *
928 * <p>When passing information to a Java subprocess,
929 * <a href=#EnvironmentVSSystemProperties>system properties</a>
930 * are generally preferred over environment variables.
931 *
932 * @return the environment as a map of variable names to values
933 * @throws SecurityException
934 * if a security manager exists and its
935 * {@link SecurityManager#checkPermission checkPermission}
936 * method doesn't allow access to the process environment
937 * @see #getenv(String)
938 * @see ProcessBuilder#environment()
939 * @since 1.5
940 */
941 public static java.util.Map<String,String> getenv() {
942 SecurityManager sm = getSecurityManager();
943 if (sm != null) {
944 sm.checkPermission(new RuntimePermission("getenv.*"));
945 }
946
947 return ProcessEnvironment.getenv();
948 }
949
950 /**
951 * Terminates the currently running Java Virtual Machine. The
952 * argument serves as a status code; by convention, a nonzero status
953 * code indicates abnormal termination.
954 * <p>
955 * This method calls the <code>exit</code> method in class
956 * <code>Runtime</code>. This method never returns normally.
957 * <p>
958 * The call <code>System.exit(n)</code> is effectively equivalent to
959 * the call:
960 * <blockquote><pre>
961 * Runtime.getRuntime().exit(n)
962 * </pre></blockquote>
963 *
964 * @param status exit status.
965 * @throws SecurityException
966 * if a security manager exists and its <code>checkExit</code>
967 * method doesn't allow exit with the specified status.
968 * @see java.lang.Runtime#exit(int)
969 */
970 public static void exit(int status) {
971 Runtime.getRuntime().exit(status);
972 }
973
974 /**
975 * Runs the garbage collector.
976 * <p>
977 * Calling the <code>gc</code> method suggests that the Java Virtual
978 * Machine expend effort toward recycling unused objects in order to
979 * make the memory they currently occupy available for quick reuse.
980 * When control returns from the method call, the Java Virtual
981 * Machine has made a best effort to reclaim space from all discarded
982 * objects.
983 * <p>
984 * The call <code>System.gc()</code> is effectively equivalent to the
985 * call:
986 * <blockquote><pre>
987 * Runtime.getRuntime().gc()
988 * </pre></blockquote>
989 *
990 * @see java.lang.Runtime#gc()
991 */
992 public static void gc() {
993 Runtime.getRuntime().gc();
994 }
995
996 /**
997 * Runs the finalization methods of any objects pending finalization.
998 * <p>
999 * Calling this method suggests that the Java Virtual Machine expend
1000 * effort toward running the <code>finalize</code> methods of objects
1001 * that have been found to be discarded but whose <code>finalize</code>
1002 * methods have not yet been run. When control returns from the
1003 * method call, the Java Virtual Machine has made a best effort to
1004 * complete all outstanding finalizations.
1005 * <p>
1006 * The call <code>System.runFinalization()</code> is effectively
1007 * equivalent to the call:
1008 * <blockquote><pre>
1009 * Runtime.getRuntime().runFinalization()
1010 * </pre></blockquote>
1011 *
1012 * @see java.lang.Runtime#runFinalization()
1013 */
1014 public static void runFinalization() {
1015 Runtime.getRuntime().runFinalization();
1016 }
1017
1018 /**
1019 * Enable or disable finalization on exit; doing so specifies that the
1020 * finalizers of all objects that have finalizers that have not yet been
1021 * automatically invoked are to be run before the Java runtime exits.
1022 * By default, finalization on exit is disabled.
1023 *
1024 * <p>If there is a security manager,
1025 * its <code>checkExit</code> method is first called
1026 * with 0 as its argument to ensure the exit is allowed.
1027 * This could result in a SecurityException.
1028 *
1029 * @deprecated This method is inherently unsafe. It may result in
1030 * finalizers being called on live objects while other threads are
1031 * concurrently manipulating those objects, resulting in erratic
1032 * behavior or deadlock.
1033 * @param value indicating enabling or disabling of finalization
1034 * @throws SecurityException
1035 * if a security manager exists and its <code>checkExit</code>
1036 * method doesn't allow the exit.
1037 *
1038 * @see java.lang.Runtime#exit(int)
1039 * @see java.lang.Runtime#gc()
1040 * @see java.lang.SecurityManager#checkExit(int)
1041 * @since JDK1.1
1042 */
1043 @Deprecated
1044 public static void runFinalizersOnExit(boolean value) {
1045 Runtime.runFinalizersOnExit(value);
1046 }
1047
1048 /**
1049 * Loads the native library specified by the filename argument. The filename
1050 * argument must be an absolute path name.
1051 *
1052 * If the filename argument, when stripped of any platform-specific library
1053 * prefix, path, and file extension, indicates a library whose name is,
1054 * for example, L, and a native library called L is statically linked
1055 * with the VM, then the JNI_OnLoad_L function exported by the library
1056 * is invoked rather than attempting to load a dynamic library.
1057 * A filename matching the argument does not have to exist in the
1058 * file system.
1059 * See the JNI Specification for more details.
1060 *
1061 * Otherwise, the filename argument is mapped to a native library image in
1062 * an implementation-dependent manner.
1063 *
1064 * <p>
1065 * The call <code>System.load(name)</code> is effectively equivalent
1066 * to the call:
1067 * <blockquote><pre>
1068 * Runtime.getRuntime().load(name)
1069 * </pre></blockquote>
1070 *
1071 * @param filename the file to load.
1072 * @exception SecurityException if a security manager exists and its
1073 * <code>checkLink</code> method doesn't allow
1074 * loading of the specified dynamic library
1075 * @exception UnsatisfiedLinkError if either the filename is not an
1076 * absolute path name, the native library is not statically
1077 * linked with the VM, or the library cannot be mapped to
1078 * a native library image by the host system.
1079 * @exception NullPointerException if <code>filename</code> is
1080 * <code>null</code>
1081 * @see java.lang.Runtime#load(java.lang.String)
1082 * @see java.lang.SecurityManager#checkLink(java.lang.String)
1083 */
1084 @CallerSensitive
1085 public static void load(String filename) {
1086 Runtime.getRuntime().load0(Reflection.getCallerClass(), filename);
1087 }
1088
1089 /**
1090 * Loads the native library specified by the <code>libname</code>
1091 * argument. The <code>libname</code> argument must not contain any platform
1092 * specific prefix, file extension or path. If a native library
1093 * called <code>libname</code> is statically linked with the VM, then the
1094 * JNI_OnLoad_<code>libname</code> function exported by the library is invoked.
1095 * See the JNI Specification for more details.
1096 *
1097 * Otherwise, the libname argument is loaded from a system library
1098 * location and mapped to a native library image in an implementation-
1099 * dependent manner.
1100 * <p>
1101 * The call <code>System.loadLibrary(name)</code> is effectively
1102 * equivalent to the call
1103 * <blockquote><pre>
1104 * Runtime.getRuntime().loadLibrary(name)
1105 * </pre></blockquote>
1106 *
1107 * @param libname the name of the library.
1108 * @exception SecurityException if a security manager exists and its
1109 * <code>checkLink</code> method doesn't allow
1110 * loading of the specified dynamic library
1111 * @exception UnsatisfiedLinkError if either the libname argument
1112 * contains a file path, the native library is not statically
1113 * linked with the VM, or the library cannot be mapped to a
1114 * native library image by the host system.
1115 * @exception NullPointerException if <code>libname</code> is
1116 * <code>null</code>
1117 * @see java.lang.Runtime#loadLibrary(java.lang.String)
1118 * @see java.lang.SecurityManager#checkLink(java.lang.String)
1119 */
1120 @CallerSensitive
1121 public static void loadLibrary(String libname) {
1122 Runtime.getRuntime().loadLibrary0(Reflection.getCallerClass(), libname);
1123 }
1124
1125 /**
1126 * Maps a library name into a platform-specific string representing
1127 * a native library.
1128 *
1129 * @param libname the name of the library.
1130 * @return a platform-dependent native library name.
1131 * @exception NullPointerException if <code>libname</code> is
1132 * <code>null</code>
1133 * @see java.lang.System#loadLibrary(java.lang.String)
1134 * @see java.lang.ClassLoader#findLibrary(java.lang.String)
1135 * @since 1.2
1136 */
1137 public static native String mapLibraryName(String libname);
1138
1139 /**
1140 * Create PrintStream for stdout/err based on encoding.
1141 */
1142 private static PrintStream newPrintStream(FileOutputStream fos, String enc) {
1143 if (enc != null) {
1144 try {
1145 return new PrintStream(new BufferedOutputStream(fos, 128), true, enc);
1146 } catch (UnsupportedEncodingException uee) {}
1147 }
1148 return new PrintStream(new BufferedOutputStream(fos, 128), true);
1149 }
1150
1151
1152 /**
1153 * Initialize the system class. Called after thread initialization.
1154 */
1155 private static void initializeSystemClass() {
1156
1157 // VM might invoke JNU_NewStringPlatform() to set those encoding
1158 // sensitive properties (user.home, user.name, boot.class.path, etc.)
1159 // during "props" initialization, in which it may need access, via
1160 // System.getProperty(), to the related system encoding property that
1161 // have been initialized (put into "props") at early stage of the
1162 // initialization. So make sure the "props" is available at the
1163 // very beginning of the initialization and all system properties to
1164 // be put into it directly.
1165 props = new Properties();
1166 initProperties(props); // initialized by the VM
1167
1168 // There are certain system configurations that may be controlled by
1169 // VM options such as the maximum amount of direct memory and
1170 // Integer cache size used to support the object identity semantics
1171 // of autoboxing. Typically, the library will obtain these values
1172 // from the properties set by the VM. If the properties are for
1173 // internal implementation use only, these properties should be
1174 // removed from the system properties.
1175 //
1176 // See java.lang.Integer.IntegerCache and the
1177 // sun.misc.VM.saveAndRemoveProperties method for example.
1178 //
1179 // Save a private copy of the system properties object that
1180 // can only be accessed by the internal implementation. Remove
1181 // certain system properties that are not intended for public access.
1182 sun.misc.VM.saveAndRemoveProperties(props);
1183
1184
1185 lineSeparator = props.getProperty("line.separator");
1186 sun.misc.Version.init();
1187
1188 FileInputStream fdIn = new FileInputStream(FileDescriptor.in);
1189 FileOutputStream fdOut = new FileOutputStream(FileDescriptor.out);
1190 FileOutputStream fdErr = new FileOutputStream(FileDescriptor.err);
1191 setIn0(new BufferedInputStream(fdIn));
1192 setOut0(newPrintStream(fdOut, props.getProperty("sun.stdout.encoding")));
1193 setErr0(newPrintStream(fdErr, props.getProperty("sun.stderr.encoding")));
1194
1195 ClassLoader.initLibraryPaths();
1196
1197 // Load the zip library now in order to keep java.util.zip.ZipFile
1198 // from trying to use itself to load this library later.
1199 loadLibrary("zip");
1200
1201 // Setup Java signal handlers for HUP, TERM, and INT (where available).
1202 Terminator.setup();
1203
1204 // Initialize any miscellenous operating system settings that need to be
1205 // set for the class libraries. Currently this is no-op everywhere except
1206 // for Windows where the process-wide error mode is set before the java.io
1207 // classes are used.
1208 sun.misc.VM.initializeOSEnvironment();
1209
1210 // The main thread is not added to its thread group in the same
1211 // way as other threads; we must do it ourselves here.
1212 Thread current = Thread.currentThread();
1213 current.getThreadGroup().add(current);
1214
1215 // register shared secrets
1216 setJavaLangAccess();
1217
1218 // Subsystems that are invoked during initialization can invoke
1219 // sun.misc.VM.isBooted() in order to avoid doing things that should
1220 // wait until the application class loader has been set up.
1221 // IMPORTANT: Ensure that this remains the last initialization action!
1222 sun.misc.VM.booted();
1223 }
1224
1225 private static void setJavaLangAccess() {
1226 // Allow privileged classes outside of java.lang
1227 sun.misc.SharedSecrets.setJavaLangAccess(new sun.misc.JavaLangAccess(){
1228 public sun.reflect.ConstantPool getConstantPool(Class<?> klass) {
1229 return klass.getConstantPool();
1230 }
1231 public boolean casAnnotationType(Class<?> klass, AnnotationType oldType, AnnotationType newType) {
1232 return klass.casAnnotationType(oldType, newType);
1233 }
1234 public AnnotationType getAnnotationType(Class<?> klass) {
1235 return klass.getAnnotationType();
1236 }
1237 public Map<Class<? extends Annotation>, Annotation> getDeclaredAnnotationMap(Class<?> klass) {
1238 return klass.getDeclaredAnnotationMap();
1239 }
1240 public byte[] getRawClassAnnotations(Class<?> klass) {
1241 return klass.getRawAnnotations();
1242 }
1243 public byte[] getRawClassTypeAnnotations(Class<?> klass) {
1244 return klass.getRawTypeAnnotations();
1245 }
1246 public byte[] getRawExecutableTypeAnnotations(Executable executable) {
1247 return Class.getExecutableTypeAnnotationBytes(executable);
1248 }
1249 public <E extends Enum<E>>
1250 E[] getEnumConstantsShared(Class<E> klass) {
1251 return klass.getEnumConstantsShared();
1252 }
1253 public void blockedOn(Thread t, Interruptible b) {
1254 t.blockedOn(b);
1255 }
1256 public void registerShutdownHook(int slot, boolean registerShutdownInProgress, Runnable hook) {
1257 Shutdown.add(slot, registerShutdownInProgress, hook);
1258 }
1259 public int getStackTraceDepth(Throwable t) {
1260 return t.getStackTraceDepth();
1261 }
1262 public StackTraceElement getStackTraceElement(Throwable t, int i) {
1263 return t.getStackTraceElement(i);
1264 }
1265 public String newStringUnsafe(char[] chars) {
1266 return new String(chars, true);
1267 }
1268 public Thread newThreadWithAcc(Runnable target, AccessControlContext acc) {
1269 return new Thread(target, acc);
1270 }
1271 public void invokeFinalize(Object o) throws Throwable {
1272 o.finalize();
1273 }
1274 });
1275 }
1276 }