1 /*
2 * Copyright (c) 1994, 2014, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25 package java.lang;
26
27 import java.io.*;
28 import java.lang.reflect.Executable;
29 import java.lang.annotation.Annotation;
30 import java.security.AccessControlContext;
31 import java.util.Properties;
32 import java.util.PropertyPermission;
33 import java.util.StringTokenizer;
34 import java.util.Map;
35 import java.security.AccessController;
36 import java.security.PrivilegedAction;
37 import java.security.AllPermission;
38 import java.nio.channels.Channel;
39 import java.nio.channels.spi.SelectorProvider;
40 import sun.nio.ch.Interruptible;
41 import sun.reflect.CallerSensitive;
42 import sun.reflect.Reflection;
43 import sun.security.util.SecurityConstants;
44 import sun.reflect.annotation.AnnotationType;
45 import jdk.internal.HotSpotIntrinsicCandidate;
46 import jdk.internal.misc.JavaLangAccess;;
47 import jdk.internal.misc.SharedSecrets;;
48
49 /**
50 * The <code>System</code> class contains several useful class fields
51 * and methods. It cannot be instantiated.
52 *
53 * <p>Among the facilities provided by the <code>System</code> class
54 * are standard input, standard output, and error output streams;
55 * access to externally defined properties and environment
56 * variables; a means of loading files and libraries; and a utility
57 * method for quickly copying a portion of an array.
58 *
59 * @author unascribed
60 * @since 1.0
61 */
62 public final class System {
63
64 /* register the natives via the static initializer.
65 *
66 * VM will invoke the initializeSystemClass method to complete
67 * the initialization for this class separated from clinit.
68 * Note that to use properties set by the VM, see the constraints
69 * described in the initializeSystemClass method.
70 */
71 private static native void registerNatives();
72 static {
73 registerNatives();
74 }
75
76 /** Don't let anyone instantiate this class */
77 private System() {
78 }
79
80 /**
81 * The "standard" input stream. This stream is already
82 * open and ready to supply input data. Typically this stream
83 * corresponds to keyboard input or another input source specified by
84 * the host environment or user.
85 */
86 public static final InputStream in = null;
87
88 /**
89 * The "standard" output stream. This stream is already
90 * open and ready to accept output data. Typically this stream
91 * corresponds to display output or another output destination
92 * specified by the host environment or user.
93 * <p>
94 * For simple stand-alone Java applications, a typical way to write
95 * a line of output data is:
96 * <blockquote><pre>
97 * System.out.println(data)
98 * </pre></blockquote>
99 * <p>
100 * See the <code>println</code> methods in class <code>PrintStream</code>.
101 *
102 * @see java.io.PrintStream#println()
103 * @see java.io.PrintStream#println(boolean)
104 * @see java.io.PrintStream#println(char)
105 * @see java.io.PrintStream#println(char[])
106 * @see java.io.PrintStream#println(double)
107 * @see java.io.PrintStream#println(float)
108 * @see java.io.PrintStream#println(int)
109 * @see java.io.PrintStream#println(long)
110 * @see java.io.PrintStream#println(java.lang.Object)
111 * @see java.io.PrintStream#println(java.lang.String)
112 */
113 public static final PrintStream out = null;
114
115 /**
116 * The "standard" error output stream. This stream is already
117 * open and ready to accept output data.
118 * <p>
119 * Typically this stream corresponds to display output or another
120 * output destination specified by the host environment or user. By
121 * convention, this output stream is used to display error messages
122 * or other information that should come to the immediate attention
123 * of a user even if the principal output stream, the value of the
124 * variable <code>out</code>, has been redirected to a file or other
125 * destination that is typically not continuously monitored.
126 */
127 public static final PrintStream err = null;
128
129 /* The security manager for the system.
130 */
131 private static volatile SecurityManager security = null;
132
133 /**
134 * Reassigns the "standard" input stream.
135 *
136 * <p>First, if there is a security manager, its <code>checkPermission</code>
137 * method is called with a <code>RuntimePermission("setIO")</code> permission
138 * to see if it's ok to reassign the "standard" input stream.
139 *
140 * @param in the new standard input stream.
141 *
142 * @throws SecurityException
143 * if a security manager exists and its
144 * <code>checkPermission</code> method doesn't allow
145 * reassigning of the standard input stream.
146 *
147 * @see SecurityManager#checkPermission
148 * @see java.lang.RuntimePermission
149 *
150 * @since 1.1
151 */
152 public static void setIn(InputStream in) {
153 checkIO();
154 setIn0(in);
155 }
156
157 /**
158 * Reassigns the "standard" output stream.
159 *
160 * <p>First, if there is a security manager, its <code>checkPermission</code>
161 * method is called with a <code>RuntimePermission("setIO")</code> permission
162 * to see if it's ok to reassign the "standard" output stream.
163 *
164 * @param out the new standard output stream
165 *
166 * @throws SecurityException
167 * if a security manager exists and its
168 * <code>checkPermission</code> method doesn't allow
169 * reassigning of the standard output stream.
170 *
171 * @see SecurityManager#checkPermission
172 * @see java.lang.RuntimePermission
173 *
174 * @since 1.1
175 */
176 public static void setOut(PrintStream out) {
177 checkIO();
178 setOut0(out);
179 }
180
181 /**
182 * Reassigns the "standard" error output stream.
183 *
184 * <p>First, if there is a security manager, its <code>checkPermission</code>
185 * method is called with a <code>RuntimePermission("setIO")</code> permission
186 * to see if it's ok to reassign the "standard" error output stream.
187 *
188 * @param err the new standard error output stream.
189 *
190 * @throws SecurityException
191 * if a security manager exists and its
192 * <code>checkPermission</code> method doesn't allow
193 * reassigning of the standard error output stream.
194 *
195 * @see SecurityManager#checkPermission
196 * @see java.lang.RuntimePermission
197 *
198 * @since 1.1
199 */
200 public static void setErr(PrintStream err) {
201 checkIO();
202 setErr0(err);
203 }
204
205 private static volatile Console cons = null;
206 /**
207 * Returns the unique {@link java.io.Console Console} object associated
208 * with the current Java virtual machine, if any.
209 *
210 * @return The system console, if any, otherwise {@code null}.
211 *
212 * @since 1.6
213 */
214 public static Console console() {
215 if (cons == null) {
216 synchronized (System.class) {
217 cons = SharedSecrets.getJavaIOAccess().console();
218 }
219 }
220 return cons;
221 }
222
223 /**
224 * Returns the channel inherited from the entity that created this
225 * Java virtual machine.
226 *
227 * <p> This method returns the channel obtained by invoking the
228 * {@link java.nio.channels.spi.SelectorProvider#inheritedChannel
229 * inheritedChannel} method of the system-wide default
230 * {@link java.nio.channels.spi.SelectorProvider} object. </p>
231 *
232 * <p> In addition to the network-oriented channels described in
233 * {@link java.nio.channels.spi.SelectorProvider#inheritedChannel
234 * inheritedChannel}, this method may return other kinds of
235 * channels in the future.
236 *
237 * @return The inherited channel, if any, otherwise {@code null}.
238 *
239 * @throws IOException
240 * If an I/O error occurs
241 *
242 * @throws SecurityException
243 * If a security manager is present and it does not
244 * permit access to the channel.
245 *
246 * @since 1.5
247 */
248 public static Channel inheritedChannel() throws IOException {
249 return SelectorProvider.provider().inheritedChannel();
250 }
251
252 private static void checkIO() {
253 SecurityManager sm = getSecurityManager();
254 if (sm != null) {
255 sm.checkPermission(new RuntimePermission("setIO"));
256 }
257 }
258
259 private static native void setIn0(InputStream in);
260 private static native void setOut0(PrintStream out);
261 private static native void setErr0(PrintStream err);
262
263 /**
264 * Sets the System security.
265 *
266 * <p> If there is a security manager already installed, this method first
267 * calls the security manager's <code>checkPermission</code> method
268 * with a <code>RuntimePermission("setSecurityManager")</code>
269 * permission to ensure it's ok to replace the existing
270 * security manager.
271 * This may result in throwing a <code>SecurityException</code>.
272 *
273 * <p> Otherwise, the argument is established as the current
274 * security manager. If the argument is <code>null</code> and no
275 * security manager has been established, then no action is taken and
276 * the method simply returns.
277 *
278 * @param s the security manager.
279 * @exception SecurityException if the security manager has already
280 * been set and its <code>checkPermission</code> method
281 * doesn't allow it to be replaced.
282 * @see #getSecurityManager
283 * @see SecurityManager#checkPermission
284 * @see java.lang.RuntimePermission
285 */
286 public static
287 void setSecurityManager(final SecurityManager s) {
288 try {
289 s.checkPackageAccess("java.lang");
290 } catch (Exception e) {
291 // no-op
292 }
293 setSecurityManager0(s);
294 }
295
296 private static synchronized
297 void setSecurityManager0(final SecurityManager s) {
298 SecurityManager sm = getSecurityManager();
299 if (sm != null) {
300 // ask the currently installed security manager if we
301 // can replace it.
302 sm.checkPermission(new RuntimePermission
303 ("setSecurityManager"));
304 }
305
306 if ((s != null) && (s.getClass().getClassLoader() != null)) {
307 // New security manager class is not on bootstrap classpath.
308 // Cause policy to get initialized before we install the new
309 // security manager, in order to prevent infinite loops when
310 // trying to initialize the policy (which usually involves
311 // accessing some security and/or system properties, which in turn
312 // calls the installed security manager's checkPermission method
313 // which will loop infinitely if there is a non-system class
314 // (in this case: the new security manager class) on the stack).
315 AccessController.doPrivileged(new PrivilegedAction<>() {
316 public Object run() {
317 s.getClass().getProtectionDomain().implies
318 (SecurityConstants.ALL_PERMISSION);
319 return null;
320 }
321 });
322 }
323
324 security = s;
325 }
326
327 /**
328 * Gets the system security interface.
329 *
330 * @return if a security manager has already been established for the
331 * current application, then that security manager is returned;
332 * otherwise, <code>null</code> is returned.
333 * @see #setSecurityManager
334 */
335 public static SecurityManager getSecurityManager() {
336 return security;
337 }
338
339 /**
340 * Returns the current time in milliseconds. Note that
341 * while the unit of time of the return value is a millisecond,
342 * the granularity of the value depends on the underlying
343 * operating system and may be larger. For example, many
344 * operating systems measure time in units of tens of
345 * milliseconds.
346 *
347 * <p> See the description of the class <code>Date</code> for
348 * a discussion of slight discrepancies that may arise between
349 * "computer time" and coordinated universal time (UTC).
350 *
351 * @return the difference, measured in milliseconds, between
352 * the current time and midnight, January 1, 1970 UTC.
353 * @see java.util.Date
354 */
355 @HotSpotIntrinsicCandidate
356 public static native long currentTimeMillis();
357
358 /**
359 * Returns the current value of the running Java Virtual Machine's
360 * high-resolution time source, in nanoseconds.
361 *
362 * <p>This method can only be used to measure elapsed time and is
363 * not related to any other notion of system or wall-clock time.
364 * The value returned represents nanoseconds since some fixed but
365 * arbitrary <i>origin</i> time (perhaps in the future, so values
366 * may be negative). The same origin is used by all invocations of
367 * this method in an instance of a Java virtual machine; other
368 * virtual machine instances are likely to use a different origin.
369 *
370 * <p>This method provides nanosecond precision, but not necessarily
371 * nanosecond resolution (that is, how frequently the value changes)
372 * - no guarantees are made except that the resolution is at least as
373 * good as that of {@link #currentTimeMillis()}.
374 *
375 * <p>Differences in successive calls that span greater than
376 * approximately 292 years (2<sup>63</sup> nanoseconds) will not
377 * correctly compute elapsed time due to numerical overflow.
378 *
379 * <p>The values returned by this method become meaningful only when
380 * the difference between two such values, obtained within the same
381 * instance of a Java virtual machine, is computed.
382 *
383 * <p>For example, to measure how long some code takes to execute:
384 * <pre> {@code
385 * long startTime = System.nanoTime();
386 * // ... the code being measured ...
387 * long elapsedNanos = System.nanoTime() - startTime;}</pre>
388 *
389 * <p>To compare elapsed time against a timeout, use <pre> {@code
390 * if (System.nanoTime() - startTime >= timeoutNanos) ...}</pre>
391 * instead of <pre> {@code
392 * if (System.nanoTime() >= startTime + timeoutNanos) ...}</pre>
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 @HotSpotIntrinsicCandidate
400 public static native long nanoTime();
401
402 /**
403 * Copies an array from the specified source array, beginning at the
404 * specified position, to the specified position of the destination array.
405 * A subsequence of array components are copied from the source
406 * array referenced by <code>src</code> to the destination array
407 * referenced by <code>dest</code>. The number of components copied is
408 * equal to the <code>length</code> argument. The components at
409 * positions <code>srcPos</code> through
410 * <code>srcPos+length-1</code> in the source array are copied into
411 * positions <code>destPos</code> through
412 * <code>destPos+length-1</code>, respectively, of the destination
413 * array.
414 * <p>
415 * If the <code>src</code> and <code>dest</code> arguments refer to the
416 * same array object, then the copying is performed as if the
417 * components at positions <code>srcPos</code> through
418 * <code>srcPos+length-1</code> were first copied to a temporary
419 * array with <code>length</code> components and then the contents of
420 * the temporary array were copied into positions
421 * <code>destPos</code> through <code>destPos+length-1</code> of the
422 * destination array.
423 * <p>
424 * If <code>dest</code> is <code>null</code>, then a
425 * <code>NullPointerException</code> is thrown.
426 * <p>
427 * If <code>src</code> is <code>null</code>, then a
428 * <code>NullPointerException</code> is thrown and the destination
429 * array is not modified.
430 * <p>
431 * Otherwise, if any of the following is true, an
432 * <code>ArrayStoreException</code> is thrown and the destination is
433 * not modified:
434 * <ul>
435 * <li>The <code>src</code> argument refers to an object that is not an
436 * array.
437 * <li>The <code>dest</code> argument refers to an object that is not an
438 * array.
439 * <li>The <code>src</code> argument and <code>dest</code> argument refer
440 * to arrays whose component types are different primitive types.
441 * <li>The <code>src</code> argument refers to an array with a primitive
442 * component type and the <code>dest</code> argument refers to an array
443 * with a reference component type.
444 * <li>The <code>src</code> argument refers to an array with a reference
445 * component type and the <code>dest</code> argument refers to an array
446 * with a primitive component type.
447 * </ul>
448 * <p>
449 * Otherwise, if any of the following is true, an
450 * <code>IndexOutOfBoundsException</code> is
451 * thrown and the destination is not modified:
452 * <ul>
453 * <li>The <code>srcPos</code> argument is negative.
454 * <li>The <code>destPos</code> argument is negative.
455 * <li>The <code>length</code> argument is negative.
456 * <li><code>srcPos+length</code> is greater than
457 * <code>src.length</code>, the length of the source array.
458 * <li><code>destPos+length</code> is greater than
459 * <code>dest.length</code>, the length of the destination array.
460 * </ul>
461 * <p>
462 * Otherwise, if any actual component of the source array from
463 * position <code>srcPos</code> through
464 * <code>srcPos+length-1</code> cannot be converted to the component
465 * type of the destination array by assignment conversion, an
466 * <code>ArrayStoreException</code> is thrown. In this case, let
467 * <b><i>k</i></b> be the smallest nonnegative integer less than
468 * length such that <code>src[srcPos+</code><i>k</i><code>]</code>
469 * cannot be converted to the component type of the destination
470 * array; when the exception is thrown, source array components from
471 * positions <code>srcPos</code> through
472 * <code>srcPos+</code><i>k</i><code>-1</code>
473 * will already have been copied to destination array positions
474 * <code>destPos</code> through
475 * <code>destPos+</code><i>k</I><code>-1</code> and no other
476 * positions of the destination array will have been modified.
477 * (Because of the restrictions already itemized, this
478 * paragraph effectively applies only to the situation where both
479 * arrays have component types that are reference types.)
480 *
481 * @param src the source array.
482 * @param srcPos starting position in the source array.
483 * @param dest the destination array.
484 * @param destPos starting position in the destination data.
485 * @param length the number of array elements to be copied.
486 * @exception IndexOutOfBoundsException if copying would cause
487 * access of data outside array bounds.
488 * @exception ArrayStoreException if an element in the <code>src</code>
489 * array could not be stored into the <code>dest</code> array
490 * because of a type mismatch.
491 * @exception NullPointerException if either <code>src</code> or
492 * <code>dest</code> is <code>null</code>.
493 */
494 @HotSpotIntrinsicCandidate
495 public static native void arraycopy(Object src, int srcPos,
496 Object dest, int destPos,
497 int length);
498
499 /**
500 * Returns the same hash code for the given object as
501 * would be returned by the default method hashCode(),
502 * whether or not the given object's class overrides
503 * hashCode().
504 * The hash code for the null reference is zero.
505 *
506 * @param x object for which the hashCode is to be calculated
507 * @return the hashCode
508 * @since 1.1
509 */
510 @HotSpotIntrinsicCandidate
511 public static native int identityHashCode(Object x);
512
513 /**
514 * System properties. The following properties are guaranteed to be defined:
515 * <dl>
516 * <dt>java.version <dd>Java version number
517 * <dt>java.vendor <dd>Java vendor specific string
518 * <dt>java.vendor.url <dd>Java vendor URL
519 * <dt>java.home <dd>Java installation directory
520 * <dt>java.class.version <dd>Java class version number
521 * <dt>java.class.path <dd>Java classpath
522 * <dt>os.name <dd>Operating System Name
523 * <dt>os.arch <dd>Operating System Architecture
524 * <dt>os.version <dd>Operating System Version
525 * <dt>file.separator <dd>File separator ("/" on Unix)
526 * <dt>path.separator <dd>Path separator (":" on Unix)
527 * <dt>line.separator <dd>Line separator ("\n" on Unix)
528 * <dt>user.name <dd>User account name
529 * <dt>user.home <dd>User home directory
530 * <dt>user.dir <dd>User's current working directory
531 * </dl>
532 */
533
534 private static Properties props;
535 private static native Properties initProperties(Properties props);
536
537 /**
538 * Determines the current system properties.
539 * <p>
540 * First, if there is a security manager, its
541 * <code>checkPropertiesAccess</code> method is called with no
542 * arguments. This may result in a security exception.
543 * <p>
544 * The current set of system properties for use by the
545 * {@link #getProperty(String)} method is returned as a
546 * <code>Properties</code> object. If there is no current set of
547 * system properties, a set of system properties is first created and
548 * initialized. This set of system properties always includes values
549 * for the following keys:
550 * <table summary="Shows property keys and associated values">
551 * <tr><th>Key</th>
552 * <th>Description of Associated Value</th></tr>
553 * <tr><td><code>java.version</code></td>
554 * <td>Java Runtime Environment version</td></tr>
555 * <tr><td><code>java.vendor</code></td>
556 * <td>Java Runtime Environment vendor</td></tr>
557 * <tr><td><code>java.vendor.url</code></td>
558 * <td>Java vendor URL</td></tr>
559 * <tr><td><code>java.home</code></td>
560 * <td>Java installation directory</td></tr>
561 * <tr><td><code>java.vm.specification.version</code></td>
562 * <td>Java Virtual Machine specification version</td></tr>
563 * <tr><td><code>java.vm.specification.vendor</code></td>
564 * <td>Java Virtual Machine specification vendor</td></tr>
565 * <tr><td><code>java.vm.specification.name</code></td>
566 * <td>Java Virtual Machine specification name</td></tr>
567 * <tr><td><code>java.vm.version</code></td>
568 * <td>Java Virtual Machine implementation version</td></tr>
569 * <tr><td><code>java.vm.vendor</code></td>
570 * <td>Java Virtual Machine implementation vendor</td></tr>
571 * <tr><td><code>java.vm.name</code></td>
572 * <td>Java Virtual Machine implementation name</td></tr>
573 * <tr><td><code>java.specification.version</code></td>
574 * <td>Java Runtime Environment specification version</td></tr>
575 * <tr><td><code>java.specification.vendor</code></td>
576 * <td>Java Runtime Environment specification vendor</td></tr>
577 * <tr><td><code>java.specification.name</code></td>
578 * <td>Java Runtime Environment specification name</td></tr>
579 * <tr><td><code>java.class.version</code></td>
580 * <td>Java class format version number</td></tr>
581 * <tr><td><code>java.class.path</code></td>
582 * <td>Java class path</td></tr>
583 * <tr><td><code>java.library.path</code></td>
584 * <td>List of paths to search when loading libraries</td></tr>
585 * <tr><td><code>java.io.tmpdir</code></td>
586 * <td>Default temp file path</td></tr>
587 * <tr><td><code>java.compiler</code></td>
588 * <td>Name of JIT compiler to use</td></tr>
589 * <tr><td><code>os.name</code></td>
590 * <td>Operating system name</td></tr>
591 * <tr><td><code>os.arch</code></td>
592 * <td>Operating system architecture</td></tr>
593 * <tr><td><code>os.version</code></td>
594 * <td>Operating system version</td></tr>
595 * <tr><td><code>file.separator</code></td>
596 * <td>File separator ("/" on UNIX)</td></tr>
597 * <tr><td><code>path.separator</code></td>
598 * <td>Path separator (":" on UNIX)</td></tr>
599 * <tr><td><code>line.separator</code></td>
600 * <td>Line separator ("\n" on UNIX)</td></tr>
601 * <tr><td><code>user.name</code></td>
602 * <td>User's account name</td></tr>
603 * <tr><td><code>user.home</code></td>
604 * <td>User's home directory</td></tr>
605 * <tr><td><code>user.dir</code></td>
606 * <td>User's current working directory</td></tr>
607 * </table>
608 * <p>
609 * Multiple paths in a system property value are separated by the path
610 * separator character of the platform.
611 * <p>
612 * Note that even if the security manager does not permit the
613 * <code>getProperties</code> operation, it may choose to permit the
614 * {@link #getProperty(String)} operation.
615 *
616 * @return the system properties
617 * @exception SecurityException if a security manager exists and its
618 * <code>checkPropertiesAccess</code> method doesn't allow access
619 * to the system properties.
620 * @see #setProperties
621 * @see java.lang.SecurityException
622 * @see java.lang.SecurityManager#checkPropertiesAccess()
623 * @see java.util.Properties
624 */
625 public static Properties getProperties() {
626 SecurityManager sm = getSecurityManager();
627 if (sm != null) {
628 sm.checkPropertiesAccess();
629 }
630
631 return props;
632 }
633
634 /**
635 * Returns the system-dependent line separator string. It always
636 * returns the same value - the initial value of the {@linkplain
637 * #getProperty(String) system property} {@code line.separator}.
638 *
639 * <p>On UNIX systems, it returns {@code "\n"}; on Microsoft
640 * Windows systems it returns {@code "\r\n"}.
641 *
642 * @return the system-dependent line separator string
643 * @since 1.7
644 */
645 public static String lineSeparator() {
646 return lineSeparator;
647 }
648
649 private static String lineSeparator;
650
651 /**
652 * Sets the system properties to the <code>Properties</code>
653 * argument.
654 * <p>
655 * First, if there is a security manager, its
656 * <code>checkPropertiesAccess</code> method is called with no
657 * arguments. This may result in a security exception.
658 * <p>
659 * The argument becomes the current set of system properties for use
660 * by the {@link #getProperty(String)} method. If the argument is
661 * <code>null</code>, then the current set of system properties is
662 * forgotten.
663 *
664 * @param props the new system properties.
665 * @exception SecurityException if a security manager exists and its
666 * <code>checkPropertiesAccess</code> method doesn't allow access
667 * to the system properties.
668 * @see #getProperties
669 * @see java.util.Properties
670 * @see java.lang.SecurityException
671 * @see java.lang.SecurityManager#checkPropertiesAccess()
672 */
673 public static void setProperties(Properties props) {
674 SecurityManager sm = getSecurityManager();
675 if (sm != null) {
676 sm.checkPropertiesAccess();
677 }
678 if (props == null) {
679 props = new Properties();
680 initProperties(props);
681 }
682 System.props = props;
683 }
684
685 /**
686 * Gets the system property indicated by the specified key.
687 * <p>
688 * First, if there is a security manager, its
689 * <code>checkPropertyAccess</code> method is called with the key as
690 * its argument. This may result in a SecurityException.
691 * <p>
692 * If there is no current set of system properties, a set of system
693 * properties is first created and initialized in the same manner as
694 * for the <code>getProperties</code> method.
695 *
696 * @param key the name of the system property.
697 * @return the string value of the system property,
698 * or <code>null</code> if there is no property with that key.
699 *
700 * @exception SecurityException if a security manager exists and its
701 * <code>checkPropertyAccess</code> method doesn't allow
702 * access to the specified system property.
703 * @exception NullPointerException if <code>key</code> is
704 * <code>null</code>.
705 * @exception IllegalArgumentException if <code>key</code> is empty.
706 * @see #setProperty
707 * @see java.lang.SecurityException
708 * @see java.lang.SecurityManager#checkPropertyAccess(java.lang.String)
709 * @see java.lang.System#getProperties()
710 */
711 public static String getProperty(String key) {
712 checkKey(key);
713 SecurityManager sm = getSecurityManager();
714 if (sm != null) {
715 sm.checkPropertyAccess(key);
716 }
717
718 return props.getProperty(key);
719 }
720
721 /**
722 * Gets the system property indicated by the specified key.
723 * <p>
724 * First, if there is a security manager, its
725 * <code>checkPropertyAccess</code> method is called with the
726 * <code>key</code> as its argument.
727 * <p>
728 * If there is no current set of system properties, a set of system
729 * properties is first created and initialized in the same manner as
730 * for the <code>getProperties</code> method.
731 *
732 * @param key the name of the system property.
733 * @param def a default value.
734 * @return the string value of the system property,
735 * or the default value if there is no property with that key.
736 *
737 * @exception SecurityException if a security manager exists and its
738 * <code>checkPropertyAccess</code> method doesn't allow
739 * access to the specified system property.
740 * @exception NullPointerException if <code>key</code> is
741 * <code>null</code>.
742 * @exception IllegalArgumentException if <code>key</code> is empty.
743 * @see #setProperty
744 * @see java.lang.SecurityManager#checkPropertyAccess(java.lang.String)
745 * @see java.lang.System#getProperties()
746 */
747 public static String getProperty(String key, String def) {
748 checkKey(key);
749 SecurityManager sm = getSecurityManager();
750 if (sm != null) {
751 sm.checkPropertyAccess(key);
752 }
753
754 return props.getProperty(key, def);
755 }
756
757 /**
758 * Sets the system property indicated by the specified key.
759 * <p>
760 * First, if a security manager exists, its
761 * <code>SecurityManager.checkPermission</code> method
762 * is called with a <code>PropertyPermission(key, "write")</code>
763 * permission. This may result in a SecurityException being thrown.
764 * If no exception is thrown, the specified property is set to the given
765 * value.
766 *
767 * @param key the name of the system property.
768 * @param value the value of the system property.
769 * @return the previous value of the system property,
770 * or <code>null</code> if it did not have one.
771 *
772 * @exception SecurityException if a security manager exists and its
773 * <code>checkPermission</code> method doesn't allow
774 * setting of the specified property.
775 * @exception NullPointerException if <code>key</code> or
776 * <code>value</code> is <code>null</code>.
777 * @exception IllegalArgumentException if <code>key</code> is empty.
778 * @see #getProperty
779 * @see java.lang.System#getProperty(java.lang.String)
780 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
781 * @see java.util.PropertyPermission
782 * @see SecurityManager#checkPermission
783 * @since 1.2
784 */
785 public static String setProperty(String key, String value) {
786 checkKey(key);
787 SecurityManager sm = getSecurityManager();
788 if (sm != null) {
789 sm.checkPermission(new PropertyPermission(key,
790 SecurityConstants.PROPERTY_WRITE_ACTION));
791 }
792
793 return (String) props.setProperty(key, value);
794 }
795
796 /**
797 * Removes the system property indicated by the specified key.
798 * <p>
799 * First, if a security manager exists, its
800 * <code>SecurityManager.checkPermission</code> method
801 * is called with a <code>PropertyPermission(key, "write")</code>
802 * permission. This may result in a SecurityException being thrown.
803 * If no exception is thrown, the specified property is removed.
804 *
805 * @param key the name of the system property to be removed.
806 * @return the previous string value of the system property,
807 * or <code>null</code> if there was no property with that key.
808 *
809 * @exception SecurityException if a security manager exists and its
810 * <code>checkPropertyAccess</code> method doesn't allow
811 * access to the specified system property.
812 * @exception NullPointerException if <code>key</code> is
813 * <code>null</code>.
814 * @exception IllegalArgumentException if <code>key</code> is empty.
815 * @see #getProperty
816 * @see #setProperty
817 * @see java.util.Properties
818 * @see java.lang.SecurityException
819 * @see java.lang.SecurityManager#checkPropertiesAccess()
820 * @since 1.5
821 */
822 public static String clearProperty(String key) {
823 checkKey(key);
824 SecurityManager sm = getSecurityManager();
825 if (sm != null) {
826 sm.checkPermission(new PropertyPermission(key, "write"));
827 }
828
829 return (String) props.remove(key);
830 }
831
832 private static void checkKey(String key) {
833 if (key == null) {
834 throw new NullPointerException("key can't be null");
835 }
836 if (key.equals("")) {
837 throw new IllegalArgumentException("key can't be empty");
838 }
839 }
840
841 /**
842 * Gets the value of the specified environment variable. An
843 * environment variable is a system-dependent external named
844 * value.
845 *
846 * <p>If a security manager exists, its
847 * {@link SecurityManager#checkPermission checkPermission}
848 * method is called with a
849 * <code>{@link RuntimePermission}("getenv."+name)</code>
850 * permission. This may result in a {@link SecurityException}
851 * being thrown. If no exception is thrown the value of the
852 * variable <code>name</code> is returned.
853 *
854 * <p><a name="EnvironmentVSSystemProperties"><i>System
855 * properties</i> and <i>environment variables</i></a> are both
856 * conceptually mappings between names and values. Both
857 * mechanisms can be used to pass user-defined information to a
858 * Java process. Environment variables have a more global effect,
859 * because they are visible to all descendants of the process
860 * which defines them, not just the immediate Java subprocess.
861 * They can have subtly different semantics, such as case
862 * insensitivity, on different operating systems. For these
863 * reasons, environment variables are more likely to have
864 * unintended side effects. It is best to use system properties
865 * where possible. Environment variables should be used when a
866 * global effect is desired, or when an external system interface
867 * requires an environment variable (such as <code>PATH</code>).
868 *
869 * <p>On UNIX systems the alphabetic case of <code>name</code> is
870 * typically significant, while on Microsoft Windows systems it is
871 * typically not. For example, the expression
872 * <code>System.getenv("FOO").equals(System.getenv("foo"))</code>
873 * is likely to be true on Microsoft Windows.
874 *
875 * @param name the name of the environment variable
876 * @return the string value of the variable, or <code>null</code>
877 * if the variable is not defined in the system environment
878 * @throws NullPointerException if <code>name</code> is <code>null</code>
879 * @throws SecurityException
880 * if a security manager exists and its
881 * {@link SecurityManager#checkPermission checkPermission}
882 * method doesn't allow access to the environment variable
883 * <code>name</code>
884 * @see #getenv()
885 * @see ProcessBuilder#environment()
886 */
887 public static String getenv(String name) {
888 SecurityManager sm = getSecurityManager();
889 if (sm != null) {
890 sm.checkPermission(new RuntimePermission("getenv."+name));
891 }
892
893 return ProcessEnvironment.getenv(name);
894 }
895
896
897 /**
898 * Returns an unmodifiable string map view of the current system environment.
899 * The environment is a system-dependent mapping from names to
900 * values which is passed from parent to child processes.
901 *
902 * <p>If the system does not support environment variables, an
903 * empty map is returned.
904 *
905 * <p>The returned map will never contain null keys or values.
906 * Attempting to query the presence of a null key or value will
907 * throw a {@link NullPointerException}. Attempting to query
908 * the presence of a key or value which is not of type
909 * {@link String} will throw a {@link ClassCastException}.
910 *
911 * <p>The returned map and its collection views may not obey the
912 * general contract of the {@link Object#equals} and
913 * {@link Object#hashCode} methods.
914 *
915 * <p>The returned map is typically case-sensitive on all platforms.
916 *
917 * <p>If a security manager exists, its
918 * {@link SecurityManager#checkPermission checkPermission}
919 * method is called with a
920 * <code>{@link RuntimePermission}("getenv.*")</code>
921 * permission. This may result in a {@link SecurityException} being
922 * thrown.
923 *
924 * <p>When passing information to a Java subprocess,
925 * <a href=#EnvironmentVSSystemProperties>system properties</a>
926 * are generally preferred over environment variables.
927 *
928 * @return the environment as a map of variable names to values
929 * @throws SecurityException
930 * if a security manager exists and its
931 * {@link SecurityManager#checkPermission checkPermission}
932 * method doesn't allow access to the process environment
933 * @see #getenv(String)
934 * @see ProcessBuilder#environment()
935 * @since 1.5
936 */
937 public static java.util.Map<String,String> getenv() {
938 SecurityManager sm = getSecurityManager();
939 if (sm != null) {
940 sm.checkPermission(new RuntimePermission("getenv.*"));
941 }
942
943 return ProcessEnvironment.getenv();
944 }
945
946 /**
947 * Terminates the currently running Java Virtual Machine. The
948 * argument serves as a status code; by convention, a nonzero status
949 * code indicates abnormal termination.
950 * <p>
951 * This method calls the <code>exit</code> method in class
952 * <code>Runtime</code>. This method never returns normally.
953 * <p>
954 * The call <code>System.exit(n)</code> is effectively equivalent to
955 * the call:
956 * <blockquote><pre>
957 * Runtime.getRuntime().exit(n)
958 * </pre></blockquote>
959 *
960 * @param status exit status.
961 * @throws SecurityException
962 * if a security manager exists and its <code>checkExit</code>
963 * method doesn't allow exit with the specified status.
964 * @see java.lang.Runtime#exit(int)
965 */
966 public static void exit(int status) {
967 Runtime.getRuntime().exit(status);
968 }
969
970 /**
971 * Runs the garbage collector.
972 * <p>
973 * Calling the <code>gc</code> method suggests that the Java Virtual
974 * Machine expend effort toward recycling unused objects in order to
975 * make the memory they currently occupy available for quick reuse.
976 * When control returns from the method call, the Java Virtual
977 * Machine has made a best effort to reclaim space from all discarded
978 * objects.
979 * <p>
980 * The call <code>System.gc()</code> is effectively equivalent to the
981 * call:
982 * <blockquote><pre>
983 * Runtime.getRuntime().gc()
984 * </pre></blockquote>
985 *
986 * @see java.lang.Runtime#gc()
987 */
988 public static void gc() {
989 Runtime.getRuntime().gc();
990 }
991
992 /**
993 * Runs the finalization methods of any objects pending finalization.
994 * <p>
995 * Calling this method suggests that the Java Virtual Machine expend
996 * effort toward running the <code>finalize</code> methods of objects
997 * that have been found to be discarded but whose <code>finalize</code>
998 * methods have not yet been run. When control returns from the
999 * method call, the Java Virtual Machine has made a best effort to
1000 * complete all outstanding finalizations.
1001 * <p>
1002 * The call <code>System.runFinalization()</code> is effectively
1003 * equivalent to the call:
1004 * <blockquote><pre>
1005 * Runtime.getRuntime().runFinalization()
1006 * </pre></blockquote>
1007 *
1008 * @see java.lang.Runtime#runFinalization()
1009 */
1010 public static void runFinalization() {
1011 Runtime.getRuntime().runFinalization();
1012 }
1013
1014 /**
1015 * Enable or disable finalization on exit; doing so specifies that the
1016 * finalizers of all objects that have finalizers that have not yet been
1017 * automatically invoked are to be run before the Java runtime exits.
1018 * By default, finalization on exit is disabled.
1019 *
1020 * <p>If there is a security manager,
1021 * its <code>checkExit</code> method is first called
1022 * with 0 as its argument to ensure the exit is allowed.
1023 * This could result in a SecurityException.
1024 *
1025 * @deprecated This method is inherently unsafe. It may result in
1026 * finalizers being called on live objects while other threads are
1027 * concurrently manipulating those objects, resulting in erratic
1028 * behavior or deadlock.
1029 * @param value indicating enabling or disabling of finalization
1030 * @throws SecurityException
1031 * if a security manager exists and its <code>checkExit</code>
1032 * method doesn't allow the exit.
1033 *
1034 * @see java.lang.Runtime#exit(int)
1035 * @see java.lang.Runtime#gc()
1036 * @see java.lang.SecurityManager#checkExit(int)
1037 * @since 1.1
1038 */
1039 @Deprecated
1040 public static void runFinalizersOnExit(boolean value) {
1041 Runtime.runFinalizersOnExit(value);
1042 }
1043
1044 /**
1045 * Loads the native library specified by the filename argument. The filename
1046 * argument must be an absolute path name.
1047 *
1048 * If the filename argument, when stripped of any platform-specific library
1049 * prefix, path, and file extension, indicates a library whose name is,
1050 * for example, L, and a native library called L is statically linked
1051 * with the VM, then the JNI_OnLoad_L function exported by the library
1052 * is invoked rather than attempting to load a dynamic library.
1053 * A filename matching the argument does not have to exist in the
1054 * file system.
1055 * See the JNI Specification for more details.
1056 *
1057 * Otherwise, the filename argument is mapped to a native library image in
1058 * an implementation-dependent manner.
1059 *
1060 * <p>
1061 * The call <code>System.load(name)</code> is effectively equivalent
1062 * to the call:
1063 * <blockquote><pre>
1064 * Runtime.getRuntime().load(name)
1065 * </pre></blockquote>
1066 *
1067 * @param filename the file to load.
1068 * @exception SecurityException if a security manager exists and its
1069 * <code>checkLink</code> method doesn't allow
1070 * loading of the specified dynamic library
1071 * @exception UnsatisfiedLinkError if either the filename is not an
1072 * absolute path name, the native library is not statically
1073 * linked with the VM, or the library cannot be mapped to
1074 * a native library image by the host system.
1075 * @exception NullPointerException if <code>filename</code> is
1076 * <code>null</code>
1077 * @see java.lang.Runtime#load(java.lang.String)
1078 * @see java.lang.SecurityManager#checkLink(java.lang.String)
1079 */
1080 @CallerSensitive
1081 public static void load(String filename) {
1082 Runtime.getRuntime().load0(Reflection.getCallerClass(), filename);
1083 }
1084
1085 /**
1086 * Loads the native library specified by the <code>libname</code>
1087 * argument. The <code>libname</code> argument must not contain any platform
1088 * specific prefix, file extension or path. If a native library
1089 * called <code>libname</code> is statically linked with the VM, then the
1090 * JNI_OnLoad_<code>libname</code> function exported by the library is invoked.
1091 * See the JNI Specification for more details.
1092 *
1093 * Otherwise, the libname argument is loaded from a system library
1094 * location and mapped to a native library image in an implementation-
1095 * dependent manner.
1096 * <p>
1097 * The call <code>System.loadLibrary(name)</code> is effectively
1098 * equivalent to the call
1099 * <blockquote><pre>
1100 * Runtime.getRuntime().loadLibrary(name)
1101 * </pre></blockquote>
1102 *
1103 * @param libname the name of the library.
1104 * @exception SecurityException if a security manager exists and its
1105 * <code>checkLink</code> method doesn't allow
1106 * loading of the specified dynamic library
1107 * @exception UnsatisfiedLinkError if either the libname argument
1108 * contains a file path, the native library is not statically
1109 * linked with the VM, or the library cannot be mapped to a
1110 * native library image by the host system.
1111 * @exception NullPointerException if <code>libname</code> is
1112 * <code>null</code>
1113 * @see java.lang.Runtime#loadLibrary(java.lang.String)
1114 * @see java.lang.SecurityManager#checkLink(java.lang.String)
1115 */
1116 @CallerSensitive
1117 public static void loadLibrary(String libname) {
1118 Runtime.getRuntime().loadLibrary0(Reflection.getCallerClass(), libname);
1119 }
1120
1121 /**
1122 * Maps a library name into a platform-specific string representing
1123 * a native library.
1124 *
1125 * @param libname the name of the library.
1126 * @return a platform-dependent native library name.
1127 * @exception NullPointerException if <code>libname</code> is
1128 * <code>null</code>
1129 * @see java.lang.System#loadLibrary(java.lang.String)
1130 * @see java.lang.ClassLoader#findLibrary(java.lang.String)
1131 * @since 1.2
1132 */
1133 public static native String mapLibraryName(String libname);
1134
1135 /**
1136 * Create PrintStream for stdout/err based on encoding.
1137 */
1138 private static PrintStream newPrintStream(FileOutputStream fos, String enc) {
1139 if (enc != null) {
1140 try {
1141 return new PrintStream(new BufferedOutputStream(fos, 128), true, enc);
1142 } catch (UnsupportedEncodingException uee) {}
1143 }
1144 return new PrintStream(new BufferedOutputStream(fos, 128), true);
1145 }
1146
1147
1148 /**
1149 * Initialize the system class. Called after thread initialization.
1150 */
1151 private static void initializeSystemClass() {
1152
1153 // VM might invoke JNU_NewStringPlatform() to set those encoding
1154 // sensitive properties (user.home, user.name, boot.class.path, etc.)
1155 // during "props" initialization, in which it may need access, via
1156 // System.getProperty(), to the related system encoding property that
1157 // have been initialized (put into "props") at early stage of the
1158 // initialization. So make sure the "props" is available at the
1159 // very beginning of the initialization and all system properties to
1160 // be put into it directly.
1161 props = new Properties();
1162 initProperties(props); // initialized by the VM
1163
1164 // There are certain system configurations that may be controlled by
1165 // VM options such as the maximum amount of direct memory and
1166 // Integer cache size used to support the object identity semantics
1167 // of autoboxing. Typically, the library will obtain these values
1168 // from the properties set by the VM. If the properties are for
1169 // internal implementation use only, these properties should be
1170 // removed from the system properties.
1171 //
1172 // See java.lang.Integer.IntegerCache and the
1173 // sun.misc.VM.saveAndRemoveProperties method for example.
1174 //
1175 // Save a private copy of the system properties object that
1176 // can only be accessed by the internal implementation. Remove
1177 // certain system properties that are not intended for public access.
1178 sun.misc.VM.saveAndRemoveProperties(props);
1179
1180
1181 lineSeparator = props.getProperty("line.separator");
1182 sun.misc.Version.init();
1183
1184 FileInputStream fdIn = new FileInputStream(FileDescriptor.in);
1185 FileOutputStream fdOut = new FileOutputStream(FileDescriptor.out);
1186 FileOutputStream fdErr = new FileOutputStream(FileDescriptor.err);
1187 setIn0(new BufferedInputStream(fdIn));
1188 setOut0(newPrintStream(fdOut, props.getProperty("sun.stdout.encoding")));
1189 setErr0(newPrintStream(fdErr, props.getProperty("sun.stderr.encoding")));
1190
1191 // Load the zip library now in order to keep java.util.zip.ZipFile
1192 // from trying to use itself to load this library later.
1193 loadLibrary("zip");
1194
1195 // Setup Java signal handlers for HUP, TERM, and INT (where available).
1196 Terminator.setup();
1197
1198 // Initialize any miscellaneous operating system settings that need to be
1199 // set for the class libraries. Currently this is no-op everywhere except
1200 // for Windows where the process-wide error mode is set before the java.io
1201 // classes are used.
1202 sun.misc.VM.initializeOSEnvironment();
1203
1204 // The main thread is not added to its thread group in the same
1205 // way as other threads; we must do it ourselves here.
1206 Thread current = Thread.currentThread();
1207 current.getThreadGroup().add(current);
1208
1209 // register shared secrets
1210 setJavaLangAccess();
1211
1212 // Subsystems that are invoked during initialization can invoke
1213 // sun.misc.VM.isBooted() in order to avoid doing things that should
1214 // wait until the application class loader has been set up.
1215 // IMPORTANT: Ensure that this remains the last initialization action!
1216 sun.misc.VM.booted();
1217 }
1218
1219 private static void setJavaLangAccess() {
1220 // Allow privileged classes outside of java.lang
1221 SharedSecrets.setJavaLangAccess(new JavaLangAccess(){
1222 public sun.reflect.ConstantPool getConstantPool(Class<?> klass) {
1223 return klass.getConstantPool();
1224 }
1225 public boolean casAnnotationType(Class<?> klass, AnnotationType oldType, AnnotationType newType) {
1226 return klass.casAnnotationType(oldType, newType);
1227 }
1228 public AnnotationType getAnnotationType(Class<?> klass) {
1229 return klass.getAnnotationType();
1230 }
1231 public Map<Class<? extends Annotation>, Annotation> getDeclaredAnnotationMap(Class<?> klass) {
1232 return klass.getDeclaredAnnotationMap();
1233 }
1234 public byte[] getRawClassAnnotations(Class<?> klass) {
1235 return klass.getRawAnnotations();
1236 }
1237 public byte[] getRawClassTypeAnnotations(Class<?> klass) {
1238 return klass.getRawTypeAnnotations();
1239 }
1240 public byte[] getRawExecutableTypeAnnotations(Executable executable) {
1241 return Class.getExecutableTypeAnnotationBytes(executable);
1242 }
1243 public <E extends Enum<E>>
1244 E[] getEnumConstantsShared(Class<E> klass) {
1245 return klass.getEnumConstantsShared();
1246 }
1247 public void blockedOn(Thread t, Interruptible b) {
1248 t.blockedOn(b);
1249 }
1250 public void registerShutdownHook(int slot, boolean registerShutdownInProgress, Runnable hook) {
1251 Shutdown.add(slot, registerShutdownInProgress, hook);
1252 }
1253 public int getStackTraceDepth(Throwable t) {
1254 return t.getStackTraceDepth();
1255 }
1256 public StackTraceElement getStackTraceElement(Throwable t, int i) {
1257 return t.getStackTraceElement(i);
1258 }
1259 public String newStringUnsafe(char[] chars) {
1260 return new String(chars, true);
1261 }
1262 public Thread newThreadWithAcc(Runnable target, AccessControlContext acc) {
1263 return new Thread(target, acc);
1264 }
1265 public void invokeFinalize(Object o) throws Throwable {
1266 o.finalize();
1267 }
1268 public void formatUnsignedLong(long val, int shift, char[] buf, int offset, int len) {
1269 Long.formatUnsignedLong(val, shift, buf, offset, len);
1270 }
1271 public void formatUnsignedInt(int val, int shift, char[] buf, int offset, int len) {
1272 Integer.formatUnsignedInt(val, shift, buf, offset, len);
1273 }
1274 });
1275 }
1276 }