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
153 */
154 public class Throwable implements Serializable {
155 /** use serialVersionUID from JDK 1.0.2 for interoperability */
156 private static final long serialVersionUID = -3042686055658047285L;
157
158 /**
159 * Native code saves some indication of the stack backtrace in this slot.
160 */
161 private transient Object backtrace;
162
163 /**
164 * Specific details about the Throwable. For example, for
165 * {@code FileNotFoundException}, this contains the name of
166 * the file that could not be found.
167 *
168 * @serial
169 */
170 private String detailMessage;
171
172 /**
173 * The throwable that caused this throwable to get thrown, or null if this
174 * throwable was not caused by another throwable, or if the causative
175 * throwable is unknown. If this field is equal to this throwable itself,
176 * it indicates that the cause of this throwable has not yet been
177 * initialized.
178 *
179 * @serial
180 * @since 1.4
181 */
182 private Throwable cause = this;
183
184 /**
185 * The stack trace, as returned by {@link #getStackTrace()}.
186 *
187 * @serial
188 * @since 1.4
189 */
190 private StackTraceElement[] stackTrace;
191 /*
192 * This field is lazily initialized on first use or serialization and
193 * nulled out when fillInStackTrace is called.
194 */
195
196 /**
197 * The list of suppressed exceptions, as returned by
198 * {@link #getSuppressedExceptions()}.
199 *
200 * @serial
201 * @since 1.7
202 */
203 private List<Throwable> suppressedExceptions = null;
204 /*
205 * This field is lazily initialized when the first suppressed
206 * exception is added.
207 *
208 * OutOfMemoryError is preallocated in the VM for better OOM
209 * diagnosability during VM initialization. Constructor can't
210 * be not invoked. If a new field to be added in the future must
211 * be initialized to non-null, it requires a synchronized VM change.
212 */
213
214 /** Message for trying to suppress a null exception. */
215 private static final String NULL_CAUSE_MESSAGE = "Cannot suppress a null exception.";
216
217 /** Caption for labeling causative exception stack traces */
218 private static final String CAUSE_CAPTION = "Caused by: ";
219
220 /** Caption for labeling suppressed exception stack traces */
221 private static final String SUPPRESSED_CAPTION = "Suppressed: ";
222
223 /**
224 * Constructs a new throwable with {@code null} as its detail message.
225 * The cause is not initialized, and may subsequently be initialized by a
226 * call to {@link #initCause}.
227 *
228 * <p>The {@link #fillInStackTrace()} method is called to initialize
229 * the stack trace data in the newly created throwable.
230 */
231 public Throwable() {
232 fillInStackTrace();
233 }
234
235 /**
236 * Constructs a new throwable with the specified detail message. The
555 */
556 public void printStackTrace(PrintStream s) {
557 printStackTrace(new WrappedPrintStream(s));
558 }
559
560 private void printStackTrace(PrintStreamOrWriter s) {
561 // Guard against malicious overrides of Throwable.equals by
562 // using a Set with identity equality semantics.
563 Set<Throwable> dejaVu =
564 Collections.newSetFromMap(new IdentityHashMap<Throwable, Boolean>());
565 dejaVu.add(this);
566
567 synchronized (s.lock()) {
568 // Print our stack trace
569 s.println(this);
570 StackTraceElement[] trace = getOurStackTrace();
571 for (StackTraceElement traceElement : trace)
572 s.println("\tat " + traceElement);
573
574 // Print suppressed exceptions, if any
575 for (Throwable se : getSuppressedExceptions())
576 se.printEnclosedStackTrace(s, trace, SUPPRESSED_CAPTION, "\t", dejaVu);
577
578 // Print cause, if any
579 Throwable ourCause = getCause();
580 if (ourCause != null)
581 ourCause.printEnclosedStackTrace(s, trace, CAUSE_CAPTION, "", dejaVu);
582 }
583 }
584
585 /**
586 * Print our stack trace as an enclosed exception for the specified
587 * stack trace.
588 */
589 private void printEnclosedStackTrace(PrintStreamOrWriter s,
590 StackTraceElement[] enclosingTrace,
591 String caption,
592 String prefix,
593 Set<Throwable> dejaVu) {
594 assert Thread.holdsLock(s.lock());
595 if (dejaVu.contains(this)) {
596 s.println("\t[CIRCULAR REFERENCE:" + this + "]");
597 } else {
598 dejaVu.add(this);
599 // Compute number of frames in common between this and enclosing trace
600 StackTraceElement[] trace = getOurStackTrace();
601 int m = trace.length - 1;
602 int n = enclosingTrace.length - 1;
603 while (m >= 0 && n >=0 && trace[m].equals(enclosingTrace[n])) {
604 m--; n--;
605 }
606 int framesInCommon = trace.length - 1 - m;
607
608 // Print our stack trace
609 s.println(prefix + caption + this);
610 for (int i = 0; i <= m; i++)
611 s.println(prefix + "\tat " + trace[i]);
612 if (framesInCommon != 0)
613 s.println(prefix + "\t... " + framesInCommon + " more");
614
615 // Print suppressed exceptions, if any
616 for (Throwable se : getSuppressedExceptions())
617 se.printEnclosedStackTrace(s, trace, SUPPRESSED_CAPTION,
618 prefix +"\t", dejaVu);
619
620 // Print cause, if any
621 Throwable ourCause = getCause();
622 if (ourCause != null)
623 ourCause.printEnclosedStackTrace(s, trace, CAUSE_CAPTION, prefix, dejaVu);
624 }
625 }
626
627 /**
628 * Prints this throwable and its backtrace to the specified
629 * print writer.
630 *
631 * @param s {@code PrintWriter} to use for output
632 * @since JDK1.1
633 */
634 public void printStackTrace(PrintWriter s) {
635 printStackTrace(new WrappedPrintWriter(s));
636 }
701 * in the sequence.
702 *
703 * <p>Some virtual machines may, under some circumstances, omit one
704 * or more stack frames from the stack trace. In the extreme case,
705 * a virtual machine that has no stack trace information concerning
706 * this throwable is permitted to return a zero-length array from this
707 * method. Generally speaking, the array returned by this method will
708 * contain one element for every frame that would be printed by
709 * {@code printStackTrace}.
710 *
711 * @return an array of stack trace elements representing the stack trace
712 * pertaining to this throwable.
713 * @since 1.4
714 */
715 public StackTraceElement[] getStackTrace() {
716 return getOurStackTrace().clone();
717 }
718
719 private synchronized StackTraceElement[] getOurStackTrace() {
720 // Initialize stack trace if this is the first call to this method
721 if (stackTrace == null) {
722 int depth = getStackTraceDepth();
723 stackTrace = new StackTraceElement[depth];
724 for (int i=0; i < depth; i++)
725 stackTrace[i] = getStackTraceElement(i);
726 }
727 return stackTrace;
728 }
729
730 /**
731 * Sets the stack trace elements that will be returned by
732 * {@link #getStackTrace()} and printed by {@link #printStackTrace()}
733 * and related methods.
734 *
735 * This method, which is designed for use by RPC frameworks and other
736 * advanced systems, allows the client to override the default
737 * stack trace that is either generated by {@link #fillInStackTrace()}
738 * when a throwable is constructed or deserialized when a throwable is
739 * read from a serialization stream.
740 *
741 * @param stackTrace the stack trace elements to be associated with
742 * this {@code Throwable}. The specified array is copied by this
743 * call; changes in the specified array after the method invocation
744 * returns will have no affect on this {@code Throwable}'s stack
745 * trace.
746 *
747 * @throws NullPointerException if {@code stackTrace} is
748 * {@code null}, or if any of the elements of
749 * {@code stackTrace} are {@code null}
750 *
751 * @since 1.4
752 */
753 public void setStackTrace(StackTraceElement[] stackTrace) {
754 StackTraceElement[] defensiveCopy = stackTrace.clone();
755 for (int i = 0; i < defensiveCopy.length; i++)
756 if (defensiveCopy[i] == null)
757 throw new NullPointerException("stackTrace[" + i + "]");
758
759 synchronized (this) {
760 this.stackTrace = defensiveCopy;
761 }
762 }
763
764 /**
765 * Returns the number of elements in the stack trace (or 0 if the stack
766 * trace is unavailable).
767 *
768 * package-protection for use by SharedSecrets.
769 */
770 native int getStackTraceDepth();
771
772 /**
773 * Returns the specified element of the stack trace.
774 *
775 * package-protection for use by SharedSecrets.
776 *
777 * @param index index of the element to return.
778 * @throws IndexOutOfBoundsException if {@code index < 0 ||
779 * index >= getStackTraceDepth() }
780 */
781 native StackTraceElement getStackTraceElement(int index);
782
783 private void readObject(ObjectInputStream s)
784 throws IOException, ClassNotFoundException {
785 s.defaultReadObject(); // read in all fields
786 List<Throwable> suppressed = null;
787 if (suppressedExceptions != null &&
788 !suppressedExceptions.isEmpty()) { // Copy Throwables to new list
789 suppressed = new ArrayList<Throwable>();
790 for (Throwable t : suppressedExceptions) {
791 if (t == null)
792 throw new NullPointerException(NULL_CAUSE_MESSAGE);
793 suppressed.add(t);
794 }
795 }
796 suppressedExceptions = suppressed;
797 }
798
799 private synchronized void writeObject(ObjectOutputStream s)
800 throws IOException
801 {
802 getOurStackTrace(); // Ensure that stackTrace field is initialized.
803 s.defaultWriteObject();
804 }
805
806 /**
807 * Adds the specified exception to the list of exceptions that
808 * were suppressed, typically by the {@code try}-with-resources
809 * statement, in order to deliver this exception.
810 *
811 * <p>Note that when one exception {@linkplain
812 * #initCause(Throwable) causes} another exception, the first
813 * exception is usually caught and then the second exception is
814 * thrown in response. In contrast, when one exception suppresses
815 * another, two exceptions are thrown in sibling code blocks, such
816 * as in a {@code try} block and in its {@code finally} block, and
817 * control flow can only continue with one exception so the second
818 * is recorded as a suppressed exception of the first.
819 *
820 * @param exception the exception to be added to the list of
821 * suppressed exceptions
822 * @throws NullPointerException if {@code exception} is null
823 * @throws IllegalArgumentException if {@code exception} is this
824 * throwable; a throwable cannot suppress itself.
825 * @since 1.7
826 */
827 public synchronized void addSuppressedException(Throwable exception) {
828 if (exception == null)
829 throw new NullPointerException(NULL_CAUSE_MESSAGE);
830 if (exception == this)
831 throw new IllegalArgumentException("Self-suppression not permitted");
832
833 if (suppressedExceptions == null)
834 suppressedExceptions = new ArrayList<Throwable>();
835 suppressedExceptions.add(exception);
836 }
837
838 private static final Throwable[] EMPTY_THROWABLE_ARRAY = new Throwable[0];
839
840 /**
841 * Returns an array containing all of the exceptions that were
842 * suppressed, typically by the {@code try}-with-resources
843 * statement, in order to deliver this exception.
844 *
845 * @return an array containing all of the exceptions that were
846 * suppressed to deliver this exception.
847 * @since 1.7
848 */
849 public synchronized Throwable[] getSuppressedExceptions() {
850 if (suppressedExceptions == null)
851 return EMPTY_THROWABLE_ARRAY;
852 else
853 return suppressedExceptions.toArray(EMPTY_THROWABLE_ARRAY);
854 }
855 }
|
1 /*
2 * Copyright (c) 1994, 2010, 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
153 */
154 public class Throwable implements Serializable {
155 /** use serialVersionUID from JDK 1.0.2 for interoperability */
156 private static final long serialVersionUID = -3042686055658047285L;
157
158 /**
159 * Native code saves some indication of the stack backtrace in this slot.
160 */
161 private transient Object backtrace;
162
163 /**
164 * Specific details about the Throwable. For example, for
165 * {@code FileNotFoundException}, this contains the name of
166 * the file that could not be found.
167 *
168 * @serial
169 */
170 private String detailMessage;
171
172 /**
173 * {@linkplain #setStackTrace(StackTraceElement[] Setting the
174 * stack trace} to a one-element array containing this sentinel
175 * value indicates future attempts to set the stack trace will be
176 * ignored. The sentinal is equal to the result of calling:<br>
177 * {@code new StackTraceElement("", "", null, Integer.MIN_VALUE)}
178 */
179 public static final StackTraceElement STACK_TRACE_SENTINEL =
180 new StackTraceElement("", "", null, Integer.MIN_VALUE);
181
182 /**
183 * A value indicating the stack trace field has not yet been initialized.
184 */
185 private static final StackTraceElement[] EMPTY_STACK = new StackTraceElement[0];
186
187 /*
188 * To allow Throwable objects to be made immutable and safely
189 * reused by the JVM, such as OutOfMemoryErrors, the three fields
190 * of Throwable that are writable in response to user actions,
191 * cause, stackTrace, and suppressedExceptions obey the following
192 * protocol:
193 *
194 * 1) The fields are initialized to a non-null sentinel value
195 * which indicates the value has logically not been set.
196 *
197 * 2) Writing a null to the field indicates further writes
198 * are forbidden
199 *
200 * 3) The sentinel value may be replaced with another non-null
201 * value.
202 *
203 * For example, implementations of the HotSpot JVM have
204 * preallocated OutOfMemoryError objects to provide for better
205 * diagnosability of that situation. These objects are created
206 * without calling the constructor for that class and the fields
207 * in question are initialized to null. To support this
208 * capability, any new fields added to Throwable that require
209 * being initialized to a non-null value require a coordinated JVM
210 * change.
211 */
212
213 /**
214 * The throwable that caused this throwable to get thrown, or null if this
215 * throwable was not caused by another throwable, or if the causative
216 * throwable is unknown. If this field is equal to this throwable itself,
217 * it indicates that the cause of this throwable has not yet been
218 * initialized.
219 *
220 * @serial
221 * @since 1.4
222 */
223 private Throwable cause = this;
224
225 /**
226 * The stack trace, as returned by {@link #getStackTrace()}.
227 *
228 * @serial
229 * @since 1.4
230 */
231 private StackTraceElement[] stackTrace = new StackTraceElement[0];
232 /*
233 * This field above is lazily initialized on first use or
234 * serialization and nulled out when fillInStackTrace is called.
235 */
236
237 // Setting this static field introduces an acceptable
238 // initialization dependency on a few java.util classes.
239 private static final List<Throwable> suppressedSentinel =
240 Collections.unmodifiableList(new ArrayList<Throwable>(0));
241
242 /**
243 * The list of suppressed exceptions, as returned by {@link
244 * #getSuppressed()}. The list is initialized to a zero-element
245 * unmodifiable sentinel list. When a serialized Throwable is
246 * read in, if the {@code suppressedExceptions} field points to a
247 * zero-element list, the field is reset to the sentinel value.
248 *
249 * @serial
250 * @since 1.7
251 */
252 private List<Throwable> suppressedExceptions = suppressedSentinel;
253
254 /** Message for trying to suppress a null exception. */
255 private static final String NULL_CAUSE_MESSAGE = "Cannot suppress a null exception.";
256
257 /** Message for trying to suppress oneself. */
258 private static final String SELF_SUPPRESSION_MESSAGE = "Self-suppression not permitted";
259
260 /** Caption for labeling causative exception stack traces */
261 private static final String CAUSE_CAPTION = "Caused by: ";
262
263 /** Caption for labeling suppressed exception stack traces */
264 private static final String SUPPRESSED_CAPTION = "Suppressed: ";
265
266 /**
267 * Constructs a new throwable with {@code null} as its detail message.
268 * The cause is not initialized, and may subsequently be initialized by a
269 * call to {@link #initCause}.
270 *
271 * <p>The {@link #fillInStackTrace()} method is called to initialize
272 * the stack trace data in the newly created throwable.
273 */
274 public Throwable() {
275 fillInStackTrace();
276 }
277
278 /**
279 * Constructs a new throwable with the specified detail message. The
598 */
599 public void printStackTrace(PrintStream s) {
600 printStackTrace(new WrappedPrintStream(s));
601 }
602
603 private void printStackTrace(PrintStreamOrWriter s) {
604 // Guard against malicious overrides of Throwable.equals by
605 // using a Set with identity equality semantics.
606 Set<Throwable> dejaVu =
607 Collections.newSetFromMap(new IdentityHashMap<Throwable, Boolean>());
608 dejaVu.add(this);
609
610 synchronized (s.lock()) {
611 // Print our stack trace
612 s.println(this);
613 StackTraceElement[] trace = getOurStackTrace();
614 for (StackTraceElement traceElement : trace)
615 s.println("\tat " + traceElement);
616
617 // Print suppressed exceptions, if any
618 for (Throwable se : getSuppressed())
619 se.printEnclosedStackTrace(s, trace, SUPPRESSED_CAPTION, "\t", dejaVu);
620
621 // Print cause, if any
622 Throwable ourCause = getCause();
623 if (ourCause != null)
624 ourCause.printEnclosedStackTrace(s, trace, CAUSE_CAPTION, "", dejaVu);
625 }
626 }
627
628 /**
629 * Print our stack trace as an enclosed exception for the specified
630 * stack trace.
631 */
632 private void printEnclosedStackTrace(PrintStreamOrWriter s,
633 StackTraceElement[] enclosingTrace,
634 String caption,
635 String prefix,
636 Set<Throwable> dejaVu) {
637 assert Thread.holdsLock(s.lock());
638 if (dejaVu.contains(this)) {
639 s.println("\t[CIRCULAR REFERENCE:" + this + "]");
640 } else {
641 dejaVu.add(this);
642 // Compute number of frames in common between this and enclosing trace
643 StackTraceElement[] trace = getOurStackTrace();
644 int m = trace.length - 1;
645 int n = enclosingTrace.length - 1;
646 while (m >= 0 && n >=0 && trace[m].equals(enclosingTrace[n])) {
647 m--; n--;
648 }
649 int framesInCommon = trace.length - 1 - m;
650
651 // Print our stack trace
652 s.println(prefix + caption + this);
653 for (int i = 0; i <= m; i++)
654 s.println(prefix + "\tat " + trace[i]);
655 if (framesInCommon != 0)
656 s.println(prefix + "\t... " + framesInCommon + " more");
657
658 // Print suppressed exceptions, if any
659 for (Throwable se : getSuppressed())
660 se.printEnclosedStackTrace(s, trace, SUPPRESSED_CAPTION,
661 prefix +"\t", dejaVu);
662
663 // Print cause, if any
664 Throwable ourCause = getCause();
665 if (ourCause != null)
666 ourCause.printEnclosedStackTrace(s, trace, CAUSE_CAPTION, prefix, dejaVu);
667 }
668 }
669
670 /**
671 * Prints this throwable and its backtrace to the specified
672 * print writer.
673 *
674 * @param s {@code PrintWriter} to use for output
675 * @since JDK1.1
676 */
677 public void printStackTrace(PrintWriter s) {
678 printStackTrace(new WrappedPrintWriter(s));
679 }
744 * in the sequence.
745 *
746 * <p>Some virtual machines may, under some circumstances, omit one
747 * or more stack frames from the stack trace. In the extreme case,
748 * a virtual machine that has no stack trace information concerning
749 * this throwable is permitted to return a zero-length array from this
750 * method. Generally speaking, the array returned by this method will
751 * contain one element for every frame that would be printed by
752 * {@code printStackTrace}.
753 *
754 * @return an array of stack trace elements representing the stack trace
755 * pertaining to this throwable.
756 * @since 1.4
757 */
758 public StackTraceElement[] getStackTrace() {
759 return getOurStackTrace().clone();
760 }
761
762 private synchronized StackTraceElement[] getOurStackTrace() {
763 // Initialize stack trace if this is the first call to this method
764 if (stackTrace == EMPTY_STACK) {
765 int depth = getStackTraceDepth();
766 stackTrace = new StackTraceElement[depth];
767 for (int i=0; i < depth; i++)
768 stackTrace[i] = getStackTraceElement(i);
769 } else if (stackTrace == null) {
770 return EMPTY_STACK;
771 }
772
773 return stackTrace;
774 }
775
776 /**
777 * Sets the stack trace elements that will be returned by
778 * {@link #getStackTrace()} and printed by {@link #printStackTrace()}
779 * and related methods.
780 *
781 * This method, which is designed for use by RPC frameworks and other
782 * advanced systems, allows the client to override the default
783 * stack trace that is either generated by {@link #fillInStackTrace()}
784 * when a throwable is constructed or deserialized when a throwable is
785 * read from a serialization stream.
786 *
787 * <p>If the stack trace is set to one-element array containing
788 * the {@linkplain #STACK_TRACE_SENTINEL stack trace sentinel}
789 * value, then future calls to this method have no effect other
790 * than validating the argument is non-null.
791 *
792 * @param stackTrace the stack trace elements to be associated with
793 * this {@code Throwable}. The specified array is copied by this
794 * call; changes in the specified array after the method invocation
795 * returns will have no affect on this {@code Throwable}'s stack
796 * trace.
797 *
798 * @throws NullPointerException if {@code stackTrace} is
799 * {@code null}, or if any of the elements of
800 * {@code stackTrace} are {@code null}
801 *
802 * @since 1.4
803 */
804 public void setStackTrace(StackTraceElement[] stackTrace) {
805 // Null-check the argument
806 StackTraceElement[] defensiveCopy = stackTrace.clone();
807
808 if (stackTrace == null)
809 return;
810
811 if (defensiveCopy.length == 1 &&
812 STACK_TRACE_SENTINEL.equals(defensiveCopy[0]))
813 defensiveCopy = null;
814 else {
815 for (int i = 0; i < defensiveCopy.length; i++)
816 if (defensiveCopy[i] == null)
817 throw new NullPointerException("stackTrace[" + i + "]");
818 }
819
820 synchronized (this) {
821 this.stackTrace = defensiveCopy;
822 }
823 }
824
825 /**
826 * Returns the number of elements in the stack trace (or 0 if the stack
827 * trace is unavailable).
828 *
829 * package-protection for use by SharedSecrets.
830 */
831 native int getStackTraceDepth();
832
833 /**
834 * Returns the specified element of the stack trace.
835 *
836 * package-protection for use by SharedSecrets.
837 *
838 * @param index index of the element to return.
839 * @throws IndexOutOfBoundsException if {@code index < 0 ||
840 * index >= getStackTraceDepth() }
841 */
842 native StackTraceElement getStackTraceElement(int index);
843
844 private void readObject(ObjectInputStream s)
845 throws IOException, ClassNotFoundException {
846 s.defaultReadObject(); // read in all fields
847 List<Throwable> suppressed = null;
848 if (suppressedExceptions != null &&
849 !suppressedExceptions.isEmpty()) { // Copy Throwables to new list
850 suppressed = new ArrayList<Throwable>(1);
851 for (Throwable t : suppressedExceptions) {
852 // Enforce constraints on suppressed exceptions in
853 // case of corrupt or malicious stream.
854 if (t == null)
855 throw new NullPointerException(NULL_CAUSE_MESSAGE);
856 if (t == this)
857 throw new IllegalArgumentException(SELF_SUPPRESSION_MESSAGE);
858 suppressed.add(t);
859 }
860 }
861
862 // If suppressed is a zero-length list, use the sentinel
863 // value.
864 if (suppressed != null && suppressed.isEmpty())
865 suppressedExceptions = suppressedSentinel;
866 else
867 suppressedExceptions = suppressed;
868
869 // Note that there are no constraints on the value the cause
870 // field can hold; both null and this are valid values for the
871 // field.
872
873 // Also note that a null stack trace indicates calls to
874 // setStackTrace do not set the stack trace.
875 }
876
877 private synchronized void writeObject(ObjectOutputStream s)
878 throws IOException {
879 // Ensure that the stackTrace field is initialized to a
880 // non-null value, if appropriate. As of JDK 7, a null stack
881 // trace field is a valid value indicating the stack trace
882 // should not be set.
883 getOurStackTrace();
884 s.defaultWriteObject();
885 }
886
887 /**
888 * Adds the specified exception to the list of exceptions that
889 * were suppressed, typically by the {@code try}-with-resources
890 * statement, in order to deliver this exception.
891 *
892 * If the first exception to be suppressed is {@code null}, that
893 * indicates suppressed exception information will <em>not</em> be
894 * recorded for this exception. Subsequent calls to this method
895 * will not record any suppressed exceptions. Otherwise,
896 * attempting to suppress {@code null} after an exception has
897 * already been successfully suppressed results in a {@code
898 * NullPointerException}.
899 *
900 * <p>Note that when one exception {@linkplain
901 * #initCause(Throwable) causes} another exception, the first
902 * exception is usually caught and then the second exception is
903 * thrown in response. In contrast, when one exception suppresses
904 * another, two exceptions are thrown in sibling code blocks, such
905 * as in a {@code try} block and in its {@code finally} block, and
906 * control flow can only continue with one exception so the second
907 * is recorded as a suppressed exception of the first.
908 *
909 * @param exception the exception to be added to the list of
910 * suppressed exceptions
911 * @throws IllegalArgumentException if {@code exception} is this
912 * throwable; a throwable cannot suppress itself.
913 * @throws NullPointerException if {@code exception} is null and
914 * an exception has already been suppressed by this exception
915 * @since 1.7
916 */
917 public synchronized void addSuppressed(Throwable exception) {
918 if (exception == this)
919 throw new IllegalArgumentException(SELF_SUPPRESSION_MESSAGE);
920
921 if (exception == null) {
922 if (suppressedExceptions == suppressedSentinel) {
923 suppressedExceptions = null; // No suppression information recorded
924 return;
925 } else
926 throw new NullPointerException(NULL_CAUSE_MESSAGE);
927 } else {
928 assert exception != null && exception != this;
929
930 if (suppressedExceptions == null) // Suppressed exceptions not recorded
931 return;
932
933 if (suppressedExceptions == suppressedSentinel)
934 suppressedExceptions = new ArrayList<Throwable>(1);
935
936 assert suppressedExceptions != suppressedSentinel;
937
938 suppressedExceptions.add(exception);
939 }
940 }
941
942 private static final Throwable[] EMPTY_THROWABLE_ARRAY = new Throwable[0];
943
944 /**
945 * Returns an array containing all of the exceptions that were
946 * suppressed, typically by the {@code try}-with-resources
947 * statement, in order to deliver this exception.
948 *
949 * If no exceptions were suppressed, an empty array is returned.
950 *
951 * @return an array containing all of the exceptions that were
952 * suppressed to deliver this exception.
953 * @since 1.7
954 */
955 public synchronized Throwable[] getSuppressed() {
956 if (suppressedExceptions == suppressedSentinel ||
957 suppressedExceptions == null)
958 return EMPTY_THROWABLE_ARRAY;
959 else
960 return suppressedExceptions.toArray(EMPTY_THROWABLE_ARRAY);
961 }
962 }
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