1 /* 2 * Copyright (c) 1995, 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 26 package java.lang; 27 28 import java.io.*; 29 import java.util.StringTokenizer; 30 import sun.reflect.CallerSensitive; 31 import sun.reflect.Reflection; 32 33 /** 34 * Every Java application has a single instance of class 35 * {@code Runtime} that allows the application to interface with 36 * the environment in which the application is running. The current 37 * runtime can be obtained from the {@code getRuntime} method. 38 * <p> 39 * An application cannot create its own instance of this class. 40 * 41 * @author unascribed 42 * @see java.lang.Runtime#getRuntime() 43 * @since 1.0 44 */ 45 46 public class Runtime { 47 private static final Runtime currentRuntime = new Runtime(); 48 49 /** 50 * Returns the runtime object associated with the current Java application. 51 * Most of the methods of class {@code Runtime} are instance 52 * methods and must be invoked with respect to the current runtime object. 53 * 54 * @return the {@code Runtime} object associated with the current 55 * Java application. 56 */ 57 public static Runtime getRuntime() { 58 return currentRuntime; 59 } 60 61 /** Don't let anyone else instantiate this class */ 62 private Runtime() {} 63 64 /** 65 * Terminates the currently running Java virtual machine by initiating its 66 * shutdown sequence. This method never returns normally. The argument 67 * serves as a status code; by convention, a nonzero status code indicates 68 * abnormal termination. 69 * 70 * <p> The virtual machine's shutdown sequence consists of two phases. In 71 * the first phase all registered {@link #addShutdownHook shutdown hooks}, 72 * if any, are started in some unspecified order and allowed to run 73 * concurrently until they finish. In the second phase all uninvoked 74 * finalizers are run if {@link #runFinalizersOnExit finalization-on-exit} 75 * has been enabled. Once this is done the virtual machine {@link #halt halts}. 76 * 77 * <p> If this method is invoked after the virtual machine has begun its 78 * shutdown sequence then if shutdown hooks are being run this method will 79 * block indefinitely. If shutdown hooks have already been run and on-exit 80 * finalization has been enabled then this method halts the virtual machine 81 * with the given status code if the status is nonzero; otherwise, it 82 * blocks indefinitely. 83 * 84 * <p> The {@link System#exit(int) System.exit} method is the 85 * conventional and convenient means of invoking this method. 86 * 87 * @param status 88 * Termination status. By convention, a nonzero status code 89 * indicates abnormal termination. 90 * 91 * @throws SecurityException 92 * If a security manager is present and its 93 * {@link SecurityManager#checkExit checkExit} method does not permit 94 * exiting with the specified status 95 * 96 * @see java.lang.SecurityException 97 * @see java.lang.SecurityManager#checkExit(int) 98 * @see #addShutdownHook 99 * @see #removeShutdownHook 100 * @see #runFinalizersOnExit 101 * @see #halt(int) 102 */ 103 public void exit(int status) { 104 SecurityManager security = System.getSecurityManager(); 105 if (security != null) { 106 security.checkExit(status); 107 } 108 Shutdown.exit(status); 109 } 110 111 /** 112 * Registers a new virtual-machine shutdown hook. 113 * 114 * <p> The Java virtual machine <i>shuts down</i> in response to two kinds 115 * of events: 116 * 117 * <ul> 118 * 119 * <li> The program <i>exits</i> normally, when the last non-daemon 120 * thread exits or when the {@link #exit exit} (equivalently, 121 * {@link System#exit(int) System.exit}) method is invoked, or 122 * 123 * <li> The virtual machine is <i>terminated</i> in response to a 124 * user interrupt, such as typing {@code ^C}, or a system-wide event, 125 * such as user logoff or system shutdown. 126 * 127 * </ul> 128 * 129 * <p> A <i>shutdown hook</i> is simply an initialized but unstarted 130 * thread. When the virtual machine begins its shutdown sequence it will 131 * start all registered shutdown hooks in some unspecified order and let 132 * them run concurrently. When all the hooks have finished it will then 133 * run all uninvoked finalizers if finalization-on-exit has been enabled. 134 * Finally, the virtual machine will halt. Note that daemon threads will 135 * continue to run during the shutdown sequence, as will non-daemon threads 136 * if shutdown was initiated by invoking the {@link #exit exit} method. 137 * 138 * <p> Once the shutdown sequence has begun it can be stopped only by 139 * invoking the {@link #halt halt} method, which forcibly 140 * terminates the virtual machine. 141 * 142 * <p> Once the shutdown sequence has begun it is impossible to register a 143 * new shutdown hook or de-register a previously-registered hook. 144 * Attempting either of these operations will cause an 145 * {@link IllegalStateException} to be thrown. 146 * 147 * <p> Shutdown hooks run at a delicate time in the life cycle of a virtual 148 * machine and should therefore be coded defensively. They should, in 149 * particular, be written to be thread-safe and to avoid deadlocks insofar 150 * as possible. They should also not rely blindly upon services that may 151 * have registered their own shutdown hooks and therefore may themselves in 152 * the process of shutting down. Attempts to use other thread-based 153 * services such as the AWT event-dispatch thread, for example, may lead to 154 * deadlocks. 155 * 156 * <p> Shutdown hooks should also finish their work quickly. When a 157 * program invokes {@link #exit exit} the expectation is 158 * that the virtual machine will promptly shut down and exit. When the 159 * virtual machine is terminated due to user logoff or system shutdown the 160 * underlying operating system may only allow a fixed amount of time in 161 * which to shut down and exit. It is therefore inadvisable to attempt any 162 * user interaction or to perform a long-running computation in a shutdown 163 * hook. 164 * 165 * <p> Uncaught exceptions are handled in shutdown hooks just as in any 166 * other thread, by invoking the 167 * {@link ThreadGroup#uncaughtException uncaughtException} method of the 168 * thread's {@link ThreadGroup} object. The default implementation of this 169 * method prints the exception's stack trace to {@link System#err} and 170 * terminates the thread; it does not cause the virtual machine to exit or 171 * halt. 172 * 173 * <p> In rare circumstances the virtual machine may <i>abort</i>, that is, 174 * stop running without shutting down cleanly. This occurs when the 175 * virtual machine is terminated externally, for example with the 176 * {@code SIGKILL} signal on Unix or the {@code TerminateProcess} call on 177 * Microsoft Windows. The virtual machine may also abort if a native 178 * method goes awry by, for example, corrupting internal data structures or 179 * attempting to access nonexistent memory. If the virtual machine aborts 180 * then no guarantee can be made about whether or not any shutdown hooks 181 * will be run. 182 * 183 * @param hook 184 * An initialized but unstarted {@link Thread} object 185 * 186 * @throws IllegalArgumentException 187 * If the specified hook has already been registered, 188 * or if it can be determined that the hook is already running or 189 * has already been run 190 * 191 * @throws IllegalStateException 192 * If the virtual machine is already in the process 193 * of shutting down 194 * 195 * @throws SecurityException 196 * If a security manager is present and it denies 197 * {@link RuntimePermission}("shutdownHooks") 198 * 199 * @see #removeShutdownHook 200 * @see #halt(int) 201 * @see #exit(int) 202 * @since 1.3 203 */ 204 public void addShutdownHook(Thread hook) { 205 SecurityManager sm = System.getSecurityManager(); 206 if (sm != null) { 207 sm.checkPermission(new RuntimePermission("shutdownHooks")); 208 } 209 ApplicationShutdownHooks.add(hook); 210 } 211 212 /** 213 * De-registers a previously-registered virtual-machine shutdown hook. 214 * 215 * @param hook the hook to remove 216 * @return {@code true} if the specified hook had previously been 217 * registered and was successfully de-registered, {@code false} 218 * otherwise. 219 * 220 * @throws IllegalStateException 221 * If the virtual machine is already in the process of shutting 222 * down 223 * 224 * @throws SecurityException 225 * If a security manager is present and it denies 226 * {@link RuntimePermission}("shutdownHooks") 227 * 228 * @see #addShutdownHook 229 * @see #exit(int) 230 * @since 1.3 231 */ 232 public boolean removeShutdownHook(Thread hook) { 233 SecurityManager sm = System.getSecurityManager(); 234 if (sm != null) { 235 sm.checkPermission(new RuntimePermission("shutdownHooks")); 236 } 237 return ApplicationShutdownHooks.remove(hook); 238 } 239 240 /** 241 * Forcibly terminates the currently running Java virtual machine. This 242 * method never returns normally. 243 * 244 * <p> This method should be used with extreme caution. Unlike the 245 * {@link #exit exit} method, this method does not cause shutdown 246 * hooks to be started and does not run uninvoked finalizers if 247 * finalization-on-exit has been enabled. If the shutdown sequence has 248 * already been initiated then this method does not wait for any running 249 * shutdown hooks or finalizers to finish their work. 250 * 251 * @param status 252 * Termination status. By convention, a nonzero status code 253 * indicates abnormal termination. If the {@link Runtime#exit exit} 254 * (equivalently, {@link System#exit(int) System.exit}) method 255 * has already been invoked then this status code 256 * will override the status code passed to that method. 257 * 258 * @throws SecurityException 259 * If a security manager is present and its 260 * {@link SecurityManager#checkExit checkExit} method 261 * does not permit an exit with the specified status 262 * 263 * @see #exit 264 * @see #addShutdownHook 265 * @see #removeShutdownHook 266 * @since 1.3 267 */ 268 public void halt(int status) { 269 SecurityManager sm = System.getSecurityManager(); 270 if (sm != null) { 271 sm.checkExit(status); 272 } 273 Shutdown.halt(status); 274 } 275 276 /** 277 * Enable or disable finalization on exit; doing so specifies that the 278 * finalizers of all objects that have finalizers that have not yet been 279 * automatically invoked are to be run before the Java runtime exits. 280 * By default, finalization on exit is disabled. 281 * 282 * <p>If there is a security manager, 283 * its {@code checkExit} method is first called 284 * with 0 as its argument to ensure the exit is allowed. 285 * This could result in a SecurityException. 286 * 287 * @param value true to enable finalization on exit, false to disable 288 * @deprecated This method is inherently unsafe. It may result in 289 * finalizers being called on live objects while other threads are 290 * concurrently manipulating those objects, resulting in erratic 291 * behavior or deadlock. 292 * This method is subject to removal in a future version of Java SE. 293 * 294 * @throws SecurityException 295 * if a security manager exists and its {@code checkExit} 296 * method doesn't allow the exit. 297 * 298 * @see java.lang.Runtime#exit(int) 299 * @see java.lang.Runtime#gc() 300 * @see java.lang.SecurityManager#checkExit(int) 301 * @since 1.1 302 */ 303 @Deprecated(since="1.2", forRemoval=true) 304 public static void runFinalizersOnExit(boolean value) { 305 SecurityManager security = System.getSecurityManager(); 306 if (security != null) { 307 try { 308 security.checkExit(0); 309 } catch (SecurityException e) { 310 throw new SecurityException("runFinalizersOnExit"); 311 } 312 } 313 Shutdown.setRunFinalizersOnExit(value); 314 } 315 316 /** 317 * Executes the specified string command in a separate process. 318 * 319 * <p>This is a convenience method. An invocation of the form 320 * {@code exec(command)} 321 * behaves in exactly the same way as the invocation 322 * {@link #exec(String, String[], File) exec}{@code (command, null, null)}. 323 * 324 * @param command a specified system command. 325 * 326 * @return A new {@link Process} object for managing the subprocess 327 * 328 * @throws SecurityException 329 * If a security manager exists and its 330 * {@link SecurityManager#checkExec checkExec} 331 * method doesn't allow creation of the subprocess 332 * 333 * @throws IOException 334 * If an I/O error occurs 335 * 336 * @throws NullPointerException 337 * If {@code command} is {@code null} 338 * 339 * @throws IllegalArgumentException 340 * If {@code command} is empty 341 * 342 * @see #exec(String[], String[], File) 343 * @see ProcessBuilder 344 */ 345 public Process exec(String command) throws IOException { 346 return exec(command, null, null); 347 } 348 349 /** 350 * Executes the specified string command in a separate process with the 351 * specified environment. 352 * 353 * <p>This is a convenience method. An invocation of the form 354 * {@code exec(command, envp)} 355 * behaves in exactly the same way as the invocation 356 * {@link #exec(String, String[], File) exec}{@code (command, envp, null)}. 357 * 358 * @param command a specified system command. 359 * 360 * @param envp array of strings, each element of which 361 * has environment variable settings in the format 362 * <i>name</i>=<i>value</i>, or 363 * {@code null} if the subprocess should inherit 364 * the environment of the current process. 365 * 366 * @return A new {@link Process} object for managing the subprocess 367 * 368 * @throws SecurityException 369 * If a security manager exists and its 370 * {@link SecurityManager#checkExec checkExec} 371 * method doesn't allow creation of the subprocess 372 * 373 * @throws IOException 374 * If an I/O error occurs 375 * 376 * @throws NullPointerException 377 * If {@code command} is {@code null}, 378 * or one of the elements of {@code envp} is {@code null} 379 * 380 * @throws IllegalArgumentException 381 * If {@code command} is empty 382 * 383 * @see #exec(String[], String[], File) 384 * @see ProcessBuilder 385 */ 386 public Process exec(String command, String[] envp) throws IOException { 387 return exec(command, envp, null); 388 } 389 390 /** 391 * Executes the specified string command in a separate process with the 392 * specified environment and working directory. 393 * 394 * <p>This is a convenience method. An invocation of the form 395 * {@code exec(command, envp, dir)} 396 * behaves in exactly the same way as the invocation 397 * {@link #exec(String[], String[], File) exec}{@code (cmdarray, envp, dir)}, 398 * where {@code cmdarray} is an array of all the tokens in 399 * {@code command}. 400 * 401 * <p>More precisely, the {@code command} string is broken 402 * into tokens using a {@link StringTokenizer} created by the call 403 * {@code new {@link StringTokenizer}(command)} with no 404 * further modification of the character categories. The tokens 405 * produced by the tokenizer are then placed in the new string 406 * array {@code cmdarray}, in the same order. 407 * 408 * @param command a specified system command. 409 * 410 * @param envp array of strings, each element of which 411 * has environment variable settings in the format 412 * <i>name</i>=<i>value</i>, or 413 * {@code null} if the subprocess should inherit 414 * the environment of the current process. 415 * 416 * @param dir the working directory of the subprocess, or 417 * {@code null} if the subprocess should inherit 418 * the working directory of the current process. 419 * 420 * @return A new {@link Process} object for managing the subprocess 421 * 422 * @throws SecurityException 423 * If a security manager exists and its 424 * {@link SecurityManager#checkExec checkExec} 425 * method doesn't allow creation of the subprocess 426 * 427 * @throws IOException 428 * If an I/O error occurs 429 * 430 * @throws NullPointerException 431 * If {@code command} is {@code null}, 432 * or one of the elements of {@code envp} is {@code null} 433 * 434 * @throws IllegalArgumentException 435 * If {@code command} is empty 436 * 437 * @see ProcessBuilder 438 * @since 1.3 439 */ 440 public Process exec(String command, String[] envp, File dir) 441 throws IOException { 442 if (command.length() == 0) 443 throw new IllegalArgumentException("Empty command"); 444 445 StringTokenizer st = new StringTokenizer(command); 446 String[] cmdarray = new String[st.countTokens()]; 447 for (int i = 0; st.hasMoreTokens(); i++) 448 cmdarray[i] = st.nextToken(); 449 return exec(cmdarray, envp, dir); 450 } 451 452 /** 453 * Executes the specified command and arguments in a separate process. 454 * 455 * <p>This is a convenience method. An invocation of the form 456 * {@code exec(cmdarray)} 457 * behaves in exactly the same way as the invocation 458 * {@link #exec(String[], String[], File) exec}{@code (cmdarray, null, null)}. 459 * 460 * @param cmdarray array containing the command to call and 461 * its arguments. 462 * 463 * @return A new {@link Process} object for managing the subprocess 464 * 465 * @throws SecurityException 466 * If a security manager exists and its 467 * {@link SecurityManager#checkExec checkExec} 468 * method doesn't allow creation of the subprocess 469 * 470 * @throws IOException 471 * If an I/O error occurs 472 * 473 * @throws NullPointerException 474 * If {@code cmdarray} is {@code null}, 475 * or one of the elements of {@code cmdarray} is {@code null} 476 * 477 * @throws IndexOutOfBoundsException 478 * If {@code cmdarray} is an empty array 479 * (has length {@code 0}) 480 * 481 * @see ProcessBuilder 482 */ 483 public Process exec(String cmdarray[]) throws IOException { 484 return exec(cmdarray, null, null); 485 } 486 487 /** 488 * Executes the specified command and arguments in a separate process 489 * with the specified environment. 490 * 491 * <p>This is a convenience method. An invocation of the form 492 * {@code exec(cmdarray, envp)} 493 * behaves in exactly the same way as the invocation 494 * {@link #exec(String[], String[], File) exec}{@code (cmdarray, envp, null)}. 495 * 496 * @param cmdarray array containing the command to call and 497 * its arguments. 498 * 499 * @param envp array of strings, each element of which 500 * has environment variable settings in the format 501 * <i>name</i>=<i>value</i>, or 502 * {@code null} if the subprocess should inherit 503 * the environment of the current process. 504 * 505 * @return A new {@link Process} object for managing the subprocess 506 * 507 * @throws SecurityException 508 * If a security manager exists and its 509 * {@link SecurityManager#checkExec checkExec} 510 * method doesn't allow creation of the subprocess 511 * 512 * @throws IOException 513 * If an I/O error occurs 514 * 515 * @throws NullPointerException 516 * If {@code cmdarray} is {@code null}, 517 * or one of the elements of {@code cmdarray} is {@code null}, 518 * or one of the elements of {@code envp} is {@code null} 519 * 520 * @throws IndexOutOfBoundsException 521 * If {@code cmdarray} is an empty array 522 * (has length {@code 0}) 523 * 524 * @see ProcessBuilder 525 */ 526 public Process exec(String[] cmdarray, String[] envp) throws IOException { 527 return exec(cmdarray, envp, null); 528 } 529 530 531 /** 532 * Executes the specified command and arguments in a separate process with 533 * the specified environment and working directory. 534 * 535 * <p>Given an array of strings {@code cmdarray}, representing the 536 * tokens of a command line, and an array of strings {@code envp}, 537 * representing "environment" variable settings, this method creates 538 * a new process in which to execute the specified command. 539 * 540 * <p>This method checks that {@code cmdarray} is a valid operating 541 * system command. Which commands are valid is system-dependent, 542 * but at the very least the command must be a non-empty list of 543 * non-null strings. 544 * 545 * <p>If {@code envp} is {@code null}, the subprocess inherits the 546 * environment settings of the current process. 547 * 548 * <p>A minimal set of system dependent environment variables may 549 * be required to start a process on some operating systems. 550 * As a result, the subprocess may inherit additional environment variable 551 * settings beyond those in the specified environment. 552 * 553 * <p>{@link ProcessBuilder#start()} is now the preferred way to 554 * start a process with a modified environment. 555 * 556 * <p>The working directory of the new subprocess is specified by {@code dir}. 557 * If {@code dir} is {@code null}, the subprocess inherits the 558 * current working directory of the current process. 559 * 560 * <p>If a security manager exists, its 561 * {@link SecurityManager#checkExec checkExec} 562 * method is invoked with the first component of the array 563 * {@code cmdarray} as its argument. This may result in a 564 * {@link SecurityException} being thrown. 565 * 566 * <p>Starting an operating system process is highly system-dependent. 567 * Among the many things that can go wrong are: 568 * <ul> 569 * <li>The operating system program file was not found. 570 * <li>Access to the program file was denied. 571 * <li>The working directory does not exist. 572 * </ul> 573 * 574 * <p>In such cases an exception will be thrown. The exact nature 575 * of the exception is system-dependent, but it will always be a 576 * subclass of {@link IOException}. 577 * 578 * <p>If the operating system does not support the creation of 579 * processes, an {@link UnsupportedOperationException} will be thrown. 580 * 581 * 582 * @param cmdarray array containing the command to call and 583 * its arguments. 584 * 585 * @param envp array of strings, each element of which 586 * has environment variable settings in the format 587 * <i>name</i>=<i>value</i>, or 588 * {@code null} if the subprocess should inherit 589 * the environment of the current process. 590 * 591 * @param dir the working directory of the subprocess, or 592 * {@code null} if the subprocess should inherit 593 * the working directory of the current process. 594 * 595 * @return A new {@link Process} object for managing the subprocess 596 * 597 * @throws SecurityException 598 * If a security manager exists and its 599 * {@link SecurityManager#checkExec checkExec} 600 * method doesn't allow creation of the subprocess 601 * 602 * @throws UnsupportedOperationException 603 * If the operating system does not support the creation of processes. 604 * 605 * @throws IOException 606 * If an I/O error occurs 607 * 608 * @throws NullPointerException 609 * If {@code cmdarray} is {@code null}, 610 * or one of the elements of {@code cmdarray} is {@code null}, 611 * or one of the elements of {@code envp} is {@code null} 612 * 613 * @throws IndexOutOfBoundsException 614 * If {@code cmdarray} is an empty array 615 * (has length {@code 0}) 616 * 617 * @see ProcessBuilder 618 * @since 1.3 619 */ 620 public Process exec(String[] cmdarray, String[] envp, File dir) 621 throws IOException { 622 return new ProcessBuilder(cmdarray) 623 .environment(envp) 624 .directory(dir) 625 .start(); 626 } 627 628 /** 629 * Returns the number of processors available to the Java virtual machine. 630 * 631 * <p> This value may change during a particular invocation of the virtual 632 * machine. Applications that are sensitive to the number of available 633 * processors should therefore occasionally poll this property and adjust 634 * their resource usage appropriately. </p> 635 * 636 * @return the maximum number of processors available to the virtual 637 * machine; never smaller than one 638 * @since 1.4 639 */ 640 public native int availableProcessors(); 641 642 /** 643 * Returns the amount of free memory in the Java Virtual Machine. 644 * Calling the 645 * {@code gc} method may result in increasing the value returned 646 * by {@code freeMemory.} 647 * 648 * @return an approximation to the total amount of memory currently 649 * available for future allocated objects, measured in bytes. 650 */ 651 public native long freeMemory(); 652 653 /** 654 * Returns the total amount of memory in the Java virtual machine. 655 * The value returned by this method may vary over time, depending on 656 * the host environment. 657 * <p> 658 * Note that the amount of memory required to hold an object of any 659 * given type may be implementation-dependent. 660 * 661 * @return the total amount of memory currently available for current 662 * and future objects, measured in bytes. 663 */ 664 public native long totalMemory(); 665 666 /** 667 * Returns the maximum amount of memory that the Java virtual machine 668 * will attempt to use. If there is no inherent limit then the value 669 * {@link java.lang.Long#MAX_VALUE} will be returned. 670 * 671 * @return the maximum amount of memory that the virtual machine will 672 * attempt to use, measured in bytes 673 * @since 1.4 674 */ 675 public native long maxMemory(); 676 677 /** 678 * Runs the garbage collector. 679 * Calling this method suggests that the Java virtual machine expend 680 * effort toward recycling unused objects in order to make the memory 681 * they currently occupy available for quick reuse. When control 682 * returns from the method call, the virtual machine has made 683 * its best effort to recycle all discarded objects. 684 * <p> 685 * The name {@code gc} stands for "garbage 686 * collector". The virtual machine performs this recycling 687 * process automatically as needed, in a separate thread, even if the 688 * {@code gc} method is not invoked explicitly. 689 * <p> 690 * The method {@link System#gc()} is the conventional and convenient 691 * means of invoking this method. 692 */ 693 public native void gc(); 694 695 /* Wormhole for calling java.lang.ref.Finalizer.runFinalization */ 696 private static native void runFinalization0(); 697 698 /** 699 * Runs the finalization methods of any objects pending finalization. 700 * Calling this method suggests that the Java virtual machine expend 701 * effort toward running the {@code finalize} methods of objects 702 * that have been found to be discarded but whose {@code finalize} 703 * methods have not yet been run. When control returns from the 704 * method call, the virtual machine has made a best effort to 705 * complete all outstanding finalizations. 706 * <p> 707 * The virtual machine performs the finalization process 708 * automatically as needed, in a separate thread, if the 709 * {@code runFinalization} method is not invoked explicitly. 710 * <p> 711 * The method {@link System#runFinalization()} is the conventional 712 * and convenient means of invoking this method. 713 * 714 * @see java.lang.Object#finalize() 715 */ 716 public void runFinalization() { 717 runFinalization0(); 718 } 719 720 /** 721 * Enables/Disables tracing of instructions. 722 * If the {@code boolean} argument is {@code true}, this 723 * method suggests that the Java virtual machine emit debugging 724 * information for each instruction in the virtual machine as it 725 * is executed. The format of this information, and the file or other 726 * output stream to which it is emitted, depends on the host environment. 727 * The virtual machine may ignore this request if it does not support 728 * this feature. The destination of the trace output is system 729 * dependent. 730 * <p> 731 * If the {@code boolean} argument is {@code false}, this 732 * method causes the virtual machine to stop performing the 733 * detailed instruction trace it is performing. 734 * 735 * @param on {@code true} to enable instruction tracing; 736 * {@code false} to disable this feature. 737 */ 738 public void traceInstructions(boolean on) { } 739 740 /** 741 * Enables/Disables tracing of method calls. 742 * If the {@code boolean} argument is {@code true}, this 743 * method suggests that the Java virtual machine emit debugging 744 * information for each method in the virtual machine as it is 745 * called. The format of this information, and the file or other output 746 * stream to which it is emitted, depends on the host environment. The 747 * virtual machine may ignore this request if it does not support 748 * this feature. 749 * <p> 750 * Calling this method with argument false suggests that the 751 * virtual machine cease emitting per-call debugging information. 752 * 753 * @param on {@code true} to enable instruction tracing; 754 * {@code false} to disable this feature. 755 */ 756 public void traceMethodCalls(boolean on) { } 757 758 /** 759 * Loads the native library specified by the filename argument. The filename 760 * argument must be an absolute path name. 761 * (for example 762 * {@code Runtime.getRuntime().load("/home/avh/lib/libX11.so");}). 763 * 764 * If the filename argument, when stripped of any platform-specific library 765 * prefix, path, and file extension, indicates a library whose name is, 766 * for example, L, and a native library called L is statically linked 767 * with the VM, then the JNI_OnLoad_L function exported by the library 768 * is invoked rather than attempting to load a dynamic library. 769 * A filename matching the argument does not have to exist in the file 770 * system. See the JNI Specification for more details. 771 * 772 * Otherwise, the filename argument is mapped to a native library image in 773 * an implementation-dependent manner. 774 * <p> 775 * First, if there is a security manager, its {@code checkLink} 776 * method is called with the {@code filename} as its argument. 777 * This may result in a security exception. 778 * <p> 779 * This is similar to the method {@link #loadLibrary(String)}, but it 780 * accepts a general file name as an argument rather than just a library 781 * name, allowing any file of native code to be loaded. 782 * <p> 783 * The method {@link System#load(String)} is the conventional and 784 * convenient means of invoking this method. 785 * 786 * @param filename the file to load. 787 * @exception SecurityException if a security manager exists and its 788 * {@code checkLink} method doesn't allow 789 * loading of the specified dynamic library 790 * @exception UnsatisfiedLinkError if either the filename is not an 791 * absolute path name, the native library is not statically 792 * linked with the VM, or the library cannot be mapped to 793 * a native library image by the host system. 794 * @exception NullPointerException if {@code filename} is 795 * {@code null} 796 * @see java.lang.Runtime#getRuntime() 797 * @see java.lang.SecurityException 798 * @see java.lang.SecurityManager#checkLink(java.lang.String) 799 */ 800 @CallerSensitive 801 public void load(String filename) { 802 load0(Reflection.getCallerClass(), filename); 803 } 804 805 synchronized void load0(Class<?> fromClass, String filename) { 806 SecurityManager security = System.getSecurityManager(); 807 if (security != null) { 808 security.checkLink(filename); 809 } 810 if (!(new File(filename).isAbsolute())) { 811 throw new UnsatisfiedLinkError( 812 "Expecting an absolute path of the library: " + filename); 813 } 814 ClassLoader.loadLibrary(fromClass, filename, true); 815 } 816 817 /** 818 * Loads the native library specified by the {@code libname} 819 * argument. The {@code libname} argument must not contain any platform 820 * specific prefix, file extension or path. If a native library 821 * called {@code libname} is statically linked with the VM, then the 822 * JNI_OnLoad_{@code libname} function exported by the library is invoked. 823 * See the JNI Specification for more details. 824 * 825 * Otherwise, the libname argument is loaded from a system library 826 * location and mapped to a native library image in an implementation- 827 * dependent manner. 828 * <p> 829 * First, if there is a security manager, its {@code checkLink} 830 * method is called with the {@code libname} as its argument. 831 * This may result in a security exception. 832 * <p> 833 * The method {@link System#loadLibrary(String)} is the conventional 834 * and convenient means of invoking this method. If native 835 * methods are to be used in the implementation of a class, a standard 836 * strategy is to put the native code in a library file (call it 837 * {@code LibFile}) and then to put a static initializer: 838 * <blockquote><pre> 839 * static { System.loadLibrary("LibFile"); } 840 * </pre></blockquote> 841 * within the class declaration. When the class is loaded and 842 * initialized, the necessary native code implementation for the native 843 * methods will then be loaded as well. 844 * <p> 845 * If this method is called more than once with the same library 846 * name, the second and subsequent calls are ignored. 847 * 848 * @param libname the name of the library. 849 * @exception SecurityException if a security manager exists and its 850 * {@code checkLink} method doesn't allow 851 * loading of the specified dynamic library 852 * @exception UnsatisfiedLinkError if either the libname argument 853 * contains a file path, the native library is not statically 854 * linked with the VM, or the library cannot be mapped to a 855 * native library image by the host system. 856 * @exception NullPointerException if {@code libname} is 857 * {@code null} 858 * @see java.lang.SecurityException 859 * @see java.lang.SecurityManager#checkLink(java.lang.String) 860 */ 861 @CallerSensitive 862 public void loadLibrary(String libname) { 863 loadLibrary0(Reflection.getCallerClass(), libname); 864 } 865 866 synchronized void loadLibrary0(Class<?> fromClass, String libname) { 867 SecurityManager security = System.getSecurityManager(); 868 if (security != null) { 869 security.checkLink(libname); 870 } 871 if (libname.indexOf((int)File.separatorChar) != -1) { 872 throw new UnsatisfiedLinkError( 873 "Directory separator should not appear in library name: " + libname); 874 } 875 ClassLoader.loadLibrary(fromClass, libname, false); 876 } 877 878 /** 879 * Creates a localized version of an input stream. This method takes 880 * an {@code InputStream} and returns an {@code InputStream} 881 * equivalent to the argument in all respects except that it is 882 * localized: as characters in the local character set are read from 883 * the stream, they are automatically converted from the local 884 * character set to Unicode. 885 * <p> 886 * If the argument is already a localized stream, it may be returned 887 * as the result. 888 * 889 * @param in InputStream to localize 890 * @return a localized input stream 891 * @see java.io.InputStream 892 * @see java.io.BufferedReader#BufferedReader(java.io.Reader) 893 * @see java.io.InputStreamReader#InputStreamReader(java.io.InputStream) 894 * @deprecated As of JDK 1.1, the preferred way to translate a byte 895 * stream in the local encoding into a character stream in Unicode is via 896 * the {@code InputStreamReader} and {@code BufferedReader} 897 * classes. 898 * This method is subject to removal in a future version of Java SE. 899 */ 900 @Deprecated(since="1.1", forRemoval=true) 901 public InputStream getLocalizedInputStream(InputStream in) { 902 return in; 903 } 904 905 /** 906 * Creates a localized version of an output stream. This method 907 * takes an {@code OutputStream} and returns an 908 * {@code OutputStream} equivalent to the argument in all respects 909 * except that it is localized: as Unicode characters are written to 910 * the stream, they are automatically converted to the local 911 * character set. 912 * <p> 913 * If the argument is already a localized stream, it may be returned 914 * as the result. 915 * 916 * @deprecated As of JDK 1.1, the preferred way to translate a 917 * Unicode character stream into a byte stream in the local encoding is via 918 * the {@code OutputStreamWriter}, {@code BufferedWriter}, and 919 * {@code PrintWriter} classes. 920 * This method is subject to removal in a future version of Java SE. 921 * 922 * @param out OutputStream to localize 923 * @return a localized output stream 924 * @see java.io.OutputStream 925 * @see java.io.BufferedWriter#BufferedWriter(java.io.Writer) 926 * @see java.io.OutputStreamWriter#OutputStreamWriter(java.io.OutputStream) 927 * @see java.io.PrintWriter#PrintWriter(java.io.OutputStream) 928 */ 929 @Deprecated(since="1.1", forRemoval=true) 930 public OutputStream getLocalizedOutputStream(OutputStream out) { 931 return out; 932 } 933 934 }