1 /* 2 * Copyright (c) 1994, 2006, 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 import java.io.*; 28 29 /** 30 * The <code>Throwable</code> class is the superclass of all errors and 31 * exceptions in the Java language. Only objects that are instances of this 32 * class (or one of its subclasses) are thrown by the Java Virtual Machine or 33 * can be thrown by the Java <code>throw</code> statement. Similarly, only 34 * this class or one of its subclasses can be the argument type in a 35 * <code>catch</code> clause. 36 * 37 * For the purposes of compile-time checking of exceptions, {@code 38 * Throwable} and any subclass of {@code Throwable} that is not also a 39 * subclass of either {@link RuntimeException} or {@link Error} are 40 * regarded as checked exceptions. 41 * 42 * <p>Instances of two subclasses, {@link java.lang.Error} and 43 * {@link java.lang.Exception}, are conventionally used to indicate 44 * that exceptional situations have occurred. Typically, these instances 45 * are freshly created in the context of the exceptional situation so 46 * as to include relevant information (such as stack trace data). 47 * 48 * <p>A throwable contains a snapshot of the execution stack of its thread at 49 * the time it was created. It can also contain a message string that gives 50 * more information about the error. Finally, it can contain a <i>cause</i>: 51 * another throwable that caused this throwable to get thrown. The cause 52 * facility is new in release 1.4. It is also known as the <i>chained 53 * exception</i> facility, as the cause can, itself, have a cause, and so on, 54 * leading to a "chain" of exceptions, each caused by another. 55 * 56 * <p>One reason that a throwable may have a cause is that the class that 57 * throws it is built atop a lower layered abstraction, and an operation on 58 * the upper layer fails due to a failure in the lower layer. It would be bad 59 * design to let the throwable thrown by the lower layer propagate outward, as 60 * it is generally unrelated to the abstraction provided by the upper layer. 61 * Further, doing so would tie the API of the upper layer to the details of 62 * its implementation, assuming the lower layer's exception was a checked 63 * exception. Throwing a "wrapped exception" (i.e., an exception containing a 64 * cause) allows the upper layer to communicate the details of the failure to 65 * its caller without incurring either of these shortcomings. It preserves 66 * the flexibility to change the implementation of the upper layer without 67 * changing its API (in particular, the set of exceptions thrown by its 68 * methods). 69 * 70 * <p>A second reason that a throwable may have a cause is that the method 71 * that throws it must conform to a general-purpose interface that does not 72 * permit the method to throw the cause directly. For example, suppose 73 * a persistent collection conforms to the {@link java.util.Collection 74 * Collection} interface, and that its persistence is implemented atop 75 * <tt>java.io</tt>. Suppose the internals of the <tt>add</tt> method 76 * can throw an {@link java.io.IOException IOException}. The implementation 77 * can communicate the details of the <tt>IOException</tt> to its caller 78 * while conforming to the <tt>Collection</tt> interface by wrapping the 79 * <tt>IOException</tt> in an appropriate unchecked exception. (The 80 * specification for the persistent collection should indicate that it is 81 * capable of throwing such exceptions.) 82 * 83 * <p>A cause can be associated with a throwable in two ways: via a 84 * constructor that takes the cause as an argument, or via the 85 * {@link #initCause(Throwable)} method. New throwable classes that 86 * wish to allow causes to be associated with them should provide constructors 87 * that take a cause and delegate (perhaps indirectly) to one of the 88 * <tt>Throwable</tt> constructors that takes a cause. For example: 89 * <pre> 90 * try { 91 * lowLevelOp(); 92 * } catch (LowLevelException le) { 93 * throw new HighLevelException(le); // Chaining-aware constructor 94 * } 95 * </pre> 96 * Because the <tt>initCause</tt> method is public, it allows a cause to be 97 * associated with any throwable, even a "legacy throwable" whose 98 * implementation predates the addition of the exception chaining mechanism to 99 * <tt>Throwable</tt>. For example: 100 * <pre> 101 * try { 102 * lowLevelOp(); 103 * } catch (LowLevelException le) { 104 * throw (HighLevelException) 105 new HighLevelException().initCause(le); // Legacy constructor 106 * } 107 * </pre> 108 * 109 * <p>Prior to release 1.4, there were many throwables that had their own 110 * non-standard exception chaining mechanisms ( 111 * {@link ExceptionInInitializerError}, {@link ClassNotFoundException}, 112 * {@link java.lang.reflect.UndeclaredThrowableException}, 113 * {@link java.lang.reflect.InvocationTargetException}, 114 * {@link java.io.WriteAbortedException}, 115 * {@link java.security.PrivilegedActionException}, 116 * {@link java.awt.print.PrinterIOException}, 117 * {@link java.rmi.RemoteException} and 118 * {@link javax.naming.NamingException}). 119 * All of these throwables have been retrofitted to 120 * use the standard exception chaining mechanism, while continuing to 121 * implement their "legacy" chaining mechanisms for compatibility. 122 * 123 * <p>Further, as of release 1.4, many general purpose <tt>Throwable</tt> 124 * classes (for example {@link Exception}, {@link RuntimeException}, 125 * {@link Error}) have been retrofitted with constructors that take 126 * a cause. This was not strictly necessary, due to the existence of the 127 * <tt>initCause</tt> method, but it is more convenient and expressive to 128 * delegate to a constructor that takes a cause. 129 * 130 * <p>By convention, class <code>Throwable</code> and its subclasses have two 131 * constructors, one that takes no arguments and one that takes a 132 * <code>String</code> argument that can be used to produce a detail message. 133 * Further, those subclasses that might likely have a cause associated with 134 * them should have two more constructors, one that takes a 135 * <code>Throwable</code> (the cause), and one that takes a 136 * <code>String</code> (the detail message) and a <code>Throwable</code> (the 137 * cause). 138 * 139 * <p>Also introduced in release 1.4 is the {@link #getStackTrace()} method, 140 * which allows programmatic access to the stack trace information that was 141 * previously available only in text form, via the various forms of the 142 * {@link #printStackTrace()} method. This information has been added to the 143 * <i>serialized representation</i> of this class so <tt>getStackTrace</tt> 144 * and <tt>printStackTrace</tt> will operate properly on a throwable that 145 * was obtained by deserialization. 146 * 147 * @author unascribed 148 * @author Josh Bloch (Added exception chaining and programmatic access to 149 * stack trace in 1.4.) 150 * @jls3 11.2 Compile-Time Checking of Exceptions 151 * @since JDK1.0 152 */ 153 public class Throwable implements Serializable { 154 /** use serialVersionUID from JDK 1.0.2 for interoperability */ 155 private static final long serialVersionUID = -3042686055658047285L; 156 157 /** 158 * Native code saves some indication of the stack backtrace in this slot. 159 */ 160 private transient Object backtrace; 161 162 /** 163 * Specific details about the Throwable. For example, for 164 * <tt>FileNotFoundException</tt>, this contains the name of 165 * the file that could not be found. 166 * 167 * @serial 168 */ 169 private String detailMessage; 170 171 /** 172 * The throwable that caused this throwable to get thrown, or null if this 173 * throwable was not caused by another throwable, or if the causative 174 * throwable is unknown. If this field is equal to this throwable itself, 175 * it indicates that the cause of this throwable has not yet been 176 * initialized. 177 * 178 * @serial 179 * @since 1.4 180 */ 181 private Throwable cause = this; 182 183 /** 184 * The stack trace, as returned by {@link #getStackTrace()}. 185 * 186 * @serial 187 * @since 1.4 188 */ 189 private StackTraceElement[] stackTrace; 190 /* 191 * This field is lazily initialized on first use or serialization and 192 * nulled out when fillInStackTrace is called. 193 */ 194 195 /** 196 * Constructs a new throwable with <code>null</code> as its detail message. 197 * The cause is not initialized, and may subsequently be initialized by a 198 * call to {@link #initCause}. 199 * 200 * <p>The {@link #fillInStackTrace()} method is called to initialize 201 * the stack trace data in the newly created throwable. 202 */ 203 public Throwable() { 204 fillInStackTrace(); 205 } 206 207 /** 208 * Constructs a new throwable with the specified detail message. The 209 * cause is not initialized, and may subsequently be initialized by 210 * a call to {@link #initCause}. 211 * 212 * <p>The {@link #fillInStackTrace()} method is called to initialize 213 * the stack trace data in the newly created throwable. 214 * 215 * @param message the detail message. The detail message is saved for 216 * later retrieval by the {@link #getMessage()} method. 217 */ 218 public Throwable(String message) { 219 fillInStackTrace(); 220 detailMessage = message; 221 } 222 223 /** 224 * Constructs a new throwable with the specified detail message and 225 * cause. <p>Note that the detail message associated with 226 * <code>cause</code> is <i>not</i> automatically incorporated in 227 * this throwable's detail message. 228 * 229 * <p>The {@link #fillInStackTrace()} method is called to initialize 230 * the stack trace data in the newly created throwable. 231 * 232 * @param message the detail message (which is saved for later retrieval 233 * by the {@link #getMessage()} method). 234 * @param cause the cause (which is saved for later retrieval by the 235 * {@link #getCause()} method). (A <tt>null</tt> value is 236 * permitted, and indicates that the cause is nonexistent or 237 * unknown.) 238 * @since 1.4 239 */ 240 public Throwable(String message, Throwable cause) { 241 fillInStackTrace(); 242 detailMessage = message; 243 this.cause = cause; 244 } 245 246 /** 247 * Constructs a new throwable with the specified cause and a detail 248 * message of <tt>(cause==null ? null : cause.toString())</tt> (which 249 * typically contains the class and detail message of <tt>cause</tt>). 250 * This constructor is useful for throwables that are little more than 251 * wrappers for other throwables (for example, {@link 252 * java.security.PrivilegedActionException}). 253 * 254 * <p>The {@link #fillInStackTrace()} method is called to initialize 255 * the stack trace data in the newly created throwable. 256 * 257 * @param cause the cause (which is saved for later retrieval by the 258 * {@link #getCause()} method). (A <tt>null</tt> value is 259 * permitted, and indicates that the cause is nonexistent or 260 * unknown.) 261 * @since 1.4 262 */ 263 public Throwable(Throwable cause) { 264 fillInStackTrace(); 265 detailMessage = (cause==null ? null : cause.toString()); 266 this.cause = cause; 267 } 268 269 /** 270 * Returns the detail message string of this throwable. 271 * 272 * @return the detail message string of this <tt>Throwable</tt> instance 273 * (which may be <tt>null</tt>). 274 */ 275 public String getMessage() { 276 return detailMessage; 277 } 278 279 /** 280 * Creates a localized description of this throwable. 281 * Subclasses may override this method in order to produce a 282 * locale-specific message. For subclasses that do not override this 283 * method, the default implementation returns the same result as 284 * <code>getMessage()</code>. 285 * 286 * @return The localized description of this throwable. 287 * @since JDK1.1 288 */ 289 public String getLocalizedMessage() { 290 return getMessage(); 291 } 292 293 /** 294 * Returns the cause of this throwable or <code>null</code> if the 295 * cause is nonexistent or unknown. (The cause is the throwable that 296 * caused this throwable to get thrown.) 297 * 298 * <p>This implementation returns the cause that was supplied via one of 299 * the constructors requiring a <tt>Throwable</tt>, or that was set after 300 * creation with the {@link #initCause(Throwable)} method. While it is 301 * typically unnecessary to override this method, a subclass can override 302 * it to return a cause set by some other means. This is appropriate for 303 * a "legacy chained throwable" that predates the addition of chained 304 * exceptions to <tt>Throwable</tt>. Note that it is <i>not</i> 305 * necessary to override any of the <tt>PrintStackTrace</tt> methods, 306 * all of which invoke the <tt>getCause</tt> method to determine the 307 * cause of a throwable. 308 * 309 * @return the cause of this throwable or <code>null</code> if the 310 * cause is nonexistent or unknown. 311 * @since 1.4 312 */ 313 public Throwable getCause() { 314 return (cause==this ? null : cause); 315 } 316 317 /** 318 * Initializes the <i>cause</i> of this throwable to the specified value. 319 * (The cause is the throwable that caused this throwable to get thrown.) 320 * 321 * <p>This method can be called at most once. It is generally called from 322 * within the constructor, or immediately after creating the 323 * throwable. If this throwable was created 324 * with {@link #Throwable(Throwable)} or 325 * {@link #Throwable(String,Throwable)}, this method cannot be called 326 * even once. 327 * 328 * @param cause the cause (which is saved for later retrieval by the 329 * {@link #getCause()} method). (A <tt>null</tt> value is 330 * permitted, and indicates that the cause is nonexistent or 331 * unknown.) 332 * @return a reference to this <code>Throwable</code> instance. 333 * @throws IllegalArgumentException if <code>cause</code> is this 334 * throwable. (A throwable cannot be its own cause.) 335 * @throws IllegalStateException if this throwable was 336 * created with {@link #Throwable(Throwable)} or 337 * {@link #Throwable(String,Throwable)}, or this method has already 338 * been called on this throwable. 339 * @since 1.4 340 */ 341 public synchronized Throwable initCause(Throwable cause) { 342 if (this.cause != this) 343 throw new IllegalStateException("Can't overwrite cause"); 344 if (cause == this) 345 throw new IllegalArgumentException("Self-causation not permitted"); 346 this.cause = cause; 347 return this; 348 } 349 350 /** 351 * Returns a short description of this throwable. 352 * The result is the concatenation of: 353 * <ul> 354 * <li> the {@linkplain Class#getName() name} of the class of this object 355 * <li> ": " (a colon and a space) 356 * <li> the result of invoking this object's {@link #getLocalizedMessage} 357 * method 358 * </ul> 359 * If <tt>getLocalizedMessage</tt> returns <tt>null</tt>, then just 360 * the class name is returned. 361 * 362 * @return a string representation of this throwable. 363 */ 364 public String toString() { 365 String s = getClass().getName(); 366 String message = getLocalizedMessage(); 367 return (message != null) ? (s + ": " + message) : s; 368 } 369 370 /** 371 * Prints this throwable and its backtrace to the 372 * standard error stream. This method prints a stack trace for this 373 * <code>Throwable</code> object on the error output stream that is 374 * the value of the field <code>System.err</code>. The first line of 375 * output contains the result of the {@link #toString()} method for 376 * this object. Remaining lines represent data previously recorded by 377 * the method {@link #fillInStackTrace()}. The format of this 378 * information depends on the implementation, but the following 379 * example may be regarded as typical: 380 * <blockquote><pre> 381 * java.lang.NullPointerException 382 * at MyClass.mash(MyClass.java:9) 383 * at MyClass.crunch(MyClass.java:6) 384 * at MyClass.main(MyClass.java:3) 385 * </pre></blockquote> 386 * This example was produced by running the program: 387 * <pre> 388 * class MyClass { 389 * public static void main(String[] args) { 390 * crunch(null); 391 * } 392 * static void crunch(int[] a) { 393 * mash(a); 394 * } 395 * static void mash(int[] b) { 396 * System.out.println(b[0]); 397 * } 398 * } 399 * </pre> 400 * The backtrace for a throwable with an initialized, non-null cause 401 * should generally include the backtrace for the cause. The format 402 * of this information depends on the implementation, but the following 403 * example may be regarded as typical: 404 * <pre> 405 * HighLevelException: MidLevelException: LowLevelException 406 * at Junk.a(Junk.java:13) 407 * at Junk.main(Junk.java:4) 408 * Caused by: MidLevelException: LowLevelException 409 * at Junk.c(Junk.java:23) 410 * at Junk.b(Junk.java:17) 411 * at Junk.a(Junk.java:11) 412 * ... 1 more 413 * Caused by: LowLevelException 414 * at Junk.e(Junk.java:30) 415 * at Junk.d(Junk.java:27) 416 * at Junk.c(Junk.java:21) 417 * ... 3 more 418 * </pre> 419 * Note the presence of lines containing the characters <tt>"..."</tt>. 420 * These lines indicate that the remainder of the stack trace for this 421 * exception matches the indicated number of frames from the bottom of the 422 * stack trace of the exception that was caused by this exception (the 423 * "enclosing" exception). This shorthand can greatly reduce the length 424 * of the output in the common case where a wrapped exception is thrown 425 * from same method as the "causative exception" is caught. The above 426 * example was produced by running the program: 427 * <pre> 428 * public class Junk { 429 * public static void main(String args[]) { 430 * try { 431 * a(); 432 * } catch(HighLevelException e) { 433 * e.printStackTrace(); 434 * } 435 * } 436 * static void a() throws HighLevelException { 437 * try { 438 * b(); 439 * } catch(MidLevelException e) { 440 * throw new HighLevelException(e); 441 * } 442 * } 443 * static void b() throws MidLevelException { 444 * c(); 445 * } 446 * static void c() throws MidLevelException { 447 * try { 448 * d(); 449 * } catch(LowLevelException e) { 450 * throw new MidLevelException(e); 451 * } 452 * } 453 * static void d() throws LowLevelException { 454 * e(); 455 * } 456 * static void e() throws LowLevelException { 457 * throw new LowLevelException(); 458 * } 459 * } 460 * 461 * class HighLevelException extends Exception { 462 * HighLevelException(Throwable cause) { super(cause); } 463 * } 464 * 465 * class MidLevelException extends Exception { 466 * MidLevelException(Throwable cause) { super(cause); } 467 * } 468 * 469 * class LowLevelException extends Exception { 470 * } 471 * </pre> 472 */ 473 public void printStackTrace() { 474 printStackTrace(System.err); 475 } 476 477 /** 478 * Prints this throwable and its backtrace to the specified print stream. 479 * 480 * @param s <code>PrintStream</code> to use for output 481 */ 482 public void printStackTrace(PrintStream s) { 483 synchronized (s) { 484 s.println(this); 485 StackTraceElement[] trace = getOurStackTrace(); 486 for (int i=0; i < trace.length; i++) 487 s.println("\tat " + trace[i]); 488 489 Throwable ourCause = getCause(); 490 if (ourCause != null) 491 ourCause.printStackTraceAsCause(s, trace); 492 } 493 } 494 495 /** 496 * Print our stack trace as a cause for the specified stack trace. 497 */ 498 private void printStackTraceAsCause(PrintStream s, 499 StackTraceElement[] causedTrace) 500 { 501 // assert Thread.holdsLock(s); 502 503 // Compute number of frames in common between this and caused 504 StackTraceElement[] trace = getOurStackTrace(); 505 int m = trace.length-1, n = causedTrace.length-1; 506 while (m >= 0 && n >=0 && trace[m].equals(causedTrace[n])) { 507 m--; n--; 508 } 509 int framesInCommon = trace.length - 1 - m; 510 511 s.println("Caused by: " + this); 512 for (int i=0; i <= m; i++) 513 s.println("\tat " + trace[i]); 514 if (framesInCommon != 0) 515 s.println("\t... " + framesInCommon + " more"); 516 517 // Recurse if we have a cause 518 Throwable ourCause = getCause(); 519 if (ourCause != null) 520 ourCause.printStackTraceAsCause(s, trace); 521 } 522 523 /** 524 * Prints this throwable and its backtrace to the specified 525 * print writer. 526 * 527 * @param s <code>PrintWriter</code> to use for output 528 * @since JDK1.1 529 */ 530 public void printStackTrace(PrintWriter s) { 531 synchronized (s) { 532 s.println(this); 533 StackTraceElement[] trace = getOurStackTrace(); 534 for (int i=0; i < trace.length; i++) 535 s.println("\tat " + trace[i]); 536 537 Throwable ourCause = getCause(); 538 if (ourCause != null) 539 ourCause.printStackTraceAsCause(s, trace); 540 } 541 } 542 543 /** 544 * Print our stack trace as a cause for the specified stack trace. 545 */ 546 private void printStackTraceAsCause(PrintWriter s, 547 StackTraceElement[] causedTrace) 548 { 549 // assert Thread.holdsLock(s); 550 551 // Compute number of frames in common between this and caused 552 StackTraceElement[] trace = getOurStackTrace(); 553 int m = trace.length-1, n = causedTrace.length-1; 554 while (m >= 0 && n >=0 && trace[m].equals(causedTrace[n])) { 555 m--; n--; 556 } 557 int framesInCommon = trace.length - 1 - m; 558 559 s.println("Caused by: " + this); 560 for (int i=0; i <= m; i++) 561 s.println("\tat " + trace[i]); 562 if (framesInCommon != 0) 563 s.println("\t... " + framesInCommon + " more"); 564 565 // Recurse if we have a cause 566 Throwable ourCause = getCause(); 567 if (ourCause != null) 568 ourCause.printStackTraceAsCause(s, trace); 569 } 570 571 /** 572 * Fills in the execution stack trace. This method records within this 573 * <code>Throwable</code> object information about the current state of 574 * the stack frames for the current thread. 575 * 576 * @return a reference to this <code>Throwable</code> instance. 577 * @see java.lang.Throwable#printStackTrace() 578 */ 579 public synchronized native Throwable fillInStackTrace(); 580 581 /** 582 * Provides programmatic access to the stack trace information printed by 583 * {@link #printStackTrace()}. Returns an array of stack trace elements, 584 * each representing one stack frame. The zeroth element of the array 585 * (assuming the array's length is non-zero) represents the top of the 586 * stack, which is the last method invocation in the sequence. Typically, 587 * this is the point at which this throwable was created and thrown. 588 * The last element of the array (assuming the array's length is non-zero) 589 * represents the bottom of the stack, which is the first method invocation 590 * in the sequence. 591 * 592 * <p>Some virtual machines may, under some circumstances, omit one 593 * or more stack frames from the stack trace. In the extreme case, 594 * a virtual machine that has no stack trace information concerning 595 * this throwable is permitted to return a zero-length array from this 596 * method. Generally speaking, the array returned by this method will 597 * contain one element for every frame that would be printed by 598 * <tt>printStackTrace</tt>. 599 * 600 * @return an array of stack trace elements representing the stack trace 601 * pertaining to this throwable. 602 * @since 1.4 603 */ 604 public StackTraceElement[] getStackTrace() { 605 return getOurStackTrace().clone(); 606 } 607 608 private synchronized StackTraceElement[] getOurStackTrace() { 609 // Initialize stack trace if this is the first call to this method 610 if (stackTrace == null) { 611 int depth = getStackTraceDepth(); 612 stackTrace = new StackTraceElement[depth]; 613 for (int i=0; i < depth; i++) 614 stackTrace[i] = getStackTraceElement(i); 615 } 616 return stackTrace; 617 } 618 619 /** 620 * Sets the stack trace elements that will be returned by 621 * {@link #getStackTrace()} and printed by {@link #printStackTrace()} 622 * and related methods. 623 * 624 * This method, which is designed for use by RPC frameworks and other 625 * advanced systems, allows the client to override the default 626 * stack trace that is either generated by {@link #fillInStackTrace()} 627 * when a throwable is constructed or deserialized when a throwable is 628 * read from a serialization stream. 629 * 630 * @param stackTrace the stack trace elements to be associated with 631 * this <code>Throwable</code>. The specified array is copied by this 632 * call; changes in the specified array after the method invocation 633 * returns will have no affect on this <code>Throwable</code>'s stack 634 * trace. 635 * 636 * @throws NullPointerException if <code>stackTrace</code> is 637 * <code>null</code>, or if any of the elements of 638 * <code>stackTrace</code> are <code>null</code> 639 * 640 * @since 1.4 641 */ 642 public void setStackTrace(StackTraceElement[] stackTrace) { 643 StackTraceElement[] defensiveCopy = stackTrace.clone(); 644 for (int i = 0; i < defensiveCopy.length; i++) 645 if (defensiveCopy[i] == null) 646 throw new NullPointerException("stackTrace[" + i + "]"); 647 648 this.stackTrace = defensiveCopy; 649 } 650 651 /** 652 * Returns the number of elements in the stack trace (or 0 if the stack 653 * trace is unavailable). 654 * 655 * package-protection for use by SharedSecrets. 656 */ 657 native int getStackTraceDepth(); 658 659 /** 660 * Returns the specified element of the stack trace. 661 * 662 * package-protection for use by SharedSecrets. 663 * 664 * @param index index of the element to return. 665 * @throws IndexOutOfBoundsException if <tt>index < 0 || 666 * index >= getStackTraceDepth() </tt> 667 */ 668 native StackTraceElement getStackTraceElement(int index); 669 670 private synchronized void writeObject(java.io.ObjectOutputStream s) 671 throws IOException 672 { 673 getOurStackTrace(); // Ensure that stackTrace field is initialized. 674 s.defaultWriteObject(); 675 } 676 }