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	/*
	* Copyright (c) 1994, 2020, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package java.lang;

	import java.io.*;
	import java.util.*;

	/**
	* The {@code Throwable} class is the superclass of all errors and
	* exceptions in the Java language. Only objects that are instances of this
	* class (or one of its subclasses) are thrown by the Java Virtual Machine or
	* can be thrown by the Java {@code throw} statement. Similarly, only
	* this class or one of its subclasses can be the argument type in a
	* {@code catch} clause.
	*
	* For the purposes of compile-time checking of exceptions, {@code
	* Throwable} and any subclass of {@code Throwable} that is not also a
	* subclass of either {@link RuntimeException} or {@link Error} are
	* regarded as checked exceptions.
	*
	* <p>Instances of two subclasses, {@link java.lang.Error} and
	* {@link java.lang.Exception}, are conventionally used to indicate
	* that exceptional situations have occurred. Typically, these instances
	* are freshly created in the context of the exceptional situation so
	* as to include relevant information (such as stack trace data).
	*
	* <p>A throwable contains a snapshot of the execution stack of its
	* thread at the time it was created. It can also contain a message
	* string that gives more information about the error. Over time, a
	* throwable can {@linkplain Throwable#addSuppressed suppress} other
	* throwables from being propagated. Finally, the throwable can also
	* contain a <i>cause</i>: another throwable that caused this
	* throwable to be constructed. The recording of this causal information
	* is referred to as the <i>chained exception</i> facility, as the
	* cause can, itself, have a cause, and so on, leading to a "chain" of
	* exceptions, each caused by another.
	*
	* <p>One reason that a throwable may have a cause is that the class that
	* throws it is built atop a lower layered abstraction, and an operation on
	* the upper layer fails due to a failure in the lower layer. It would be bad
	* design to let the throwable thrown by the lower layer propagate outward, as
	* it is generally unrelated to the abstraction provided by the upper layer.
	* Further, doing so would tie the API of the upper layer to the details of
	* its implementation, assuming the lower layer's exception was a checked
	* exception. Throwing a "wrapped exception" (i.e., an exception containing a
	* cause) allows the upper layer to communicate the details of the failure to
	* its caller without incurring either of these shortcomings. It preserves
	* the flexibility to change the implementation of the upper layer without
	* changing its API (in particular, the set of exceptions thrown by its
	* methods).
	*
	* <p>A second reason that a throwable may have a cause is that the method
	* that throws it must conform to a general-purpose interface that does not
	* permit the method to throw the cause directly. For example, suppose
	* a persistent collection conforms to the {@link java.util.Collection
	* Collection} interface, and that its persistence is implemented atop
	* {@code java.io}. Suppose the internals of the {@code add} method
	* can throw an {@link java.io.IOException IOException}. The implementation
	* can communicate the details of the {@code IOException} to its caller
	* while conforming to the {@code Collection} interface by wrapping the
	* {@code IOException} in an appropriate unchecked exception. (The
	* specification for the persistent collection should indicate that it is
	* capable of throwing such exceptions.)
	*
	* <p>A cause can be associated with a throwable in two ways: via a
	* constructor that takes the cause as an argument, or via the
	* {@link #initCause(Throwable)} method. New throwable classes that
	* wish to allow causes to be associated with them should provide constructors
	* that take a cause and delegate (perhaps indirectly) to one of the
	* {@code Throwable} constructors that takes a cause.
	*
	* Because the {@code initCause} method is public, it allows a cause to be
	* associated with any throwable, even a "legacy throwable" whose
	* implementation predates the addition of the exception chaining mechanism to
	* {@code Throwable}.
	*
	* <p>By convention, class {@code Throwable} and its subclasses have two
	* constructors, one that takes no arguments and one that takes a
	* {@code String} argument that can be used to produce a detail message.
	* Further, those subclasses that might likely have a cause associated with
	* them should have two more constructors, one that takes a
	* {@code Throwable} (the cause), and one that takes a
	* {@code String} (the detail message) and a {@code Throwable} (the
	* cause).
	*
	* @author Josh Bloch (Added exception chaining and programmatic access to
	* stack trace in 1.4.)
	* @jls 11.2 Compile-Time Checking of Exceptions
	* @since 1.0
	*/
	public class Throwable implements Serializable {
	/** use serialVersionUID from JDK 1.0.2 for interoperability */
	@java.io.Serial
	private static final long serialVersionUID = -3042686055658047285L;

	/**
	* The JVM saves some indication of the stack backtrace in this slot.
	*/
	private transient Object backtrace;

	/**
	* Specific details about the Throwable. For example, for
	* {@code FileNotFoundException}, this contains the name of
	* the file that could not be found.
	*
	* @serial
	*/
	private String detailMessage;


	/**
	* Holder class to defer initializing sentinel objects only used
	* for serialization.
	*/
	private static class SentinelHolder {
	/**
	* {@linkplain #setStackTrace(StackTraceElement[]) Setting the
	* stack trace} to a one-element array containing this sentinel
	* value indicates future attempts to set the stack trace will be
	* ignored. The sentinel is equal to the result of calling:<br>
	* {@code new StackTraceElement("", "", null, Integer.MIN_VALUE)}
	*/
	public static final StackTraceElement STACK_TRACE_ELEMENT_SENTINEL =
	new StackTraceElement("", "", null, Integer.MIN_VALUE);

	/**
	* Sentinel value used in the serial form to indicate an immutable
	* stack trace.
	*/
	public static final StackTraceElement[] STACK_TRACE_SENTINEL =
	new StackTraceElement[] {STACK_TRACE_ELEMENT_SENTINEL};
	}

	/**
	* A shared value for an empty stack.
	*/
	private static final StackTraceElement[] UNASSIGNED_STACK = new StackTraceElement[0];

	/*
	* To allow Throwable objects to be made immutable and safely
	* reused by the JVM, such as OutOfMemoryErrors, fields of
	* Throwable that are writable in response to user actions, cause,
	* stackTrace, and suppressedExceptions obey the following
	* protocol:
	*
	* 1) The fields are initialized to a non-null sentinel value
	* which indicates the value has logically not been set.
	*
	* 2) Writing a null to the field indicates further writes
	* are forbidden
	*
	* 3) The sentinel value may be replaced with another non-null
	* value.
	*
	* For example, implementations of the HotSpot JVM have
	* preallocated OutOfMemoryError objects to provide for better
	* diagnosability of that situation. These objects are created
	* without calling the constructor for that class and the fields
	* in question are initialized to null. To support this
	* capability, any new fields added to Throwable that require
	* being initialized to a non-null value require a coordinated JVM
	* change.
	*/

	/**
	* The throwable that caused this throwable to get thrown, or null if this
	* throwable was not caused by another throwable, or if the causative
	* throwable is unknown. If this field is equal to this throwable itself,
	* it indicates that the cause of this throwable has not yet been
	* initialized.
	*
	* @serial
	* @since 1.4
	*/
	private Throwable cause = this;

	/**
	* The stack trace, as returned by {@link #getStackTrace()}.
	*
	* The field is initialized to a zero-length array. A {@code
	* null} value of this field indicates subsequent calls to {@link
	* #setStackTrace(StackTraceElement[])} and {@link
	* #fillInStackTrace()} will be no-ops.
	*
	* @serial
	* @since 1.4
	*/
	private StackTraceElement[] stackTrace = UNASSIGNED_STACK;

	/**
	* The JVM code sets the depth of the backtrace for later retrieval
	*/
	private transient int depth;

	// Setting this static field introduces an acceptable
	// initialization dependency on a few java.util classes.
	private static final List<Throwable> SUPPRESSED_SENTINEL = Collections.emptyList();

	/**
	* The list of suppressed exceptions, as returned by {@link
	* #getSuppressed()}. The list is initialized to a zero-element
	* unmodifiable sentinel list. When a serialized Throwable is
	* read in, if the {@code suppressedExceptions} field points to a
	* zero-element list, the field is reset to the sentinel value.
	*
	* @serial
	* @since 1.7
	*/
	@SuppressWarnings("serial") // Not statically typed as Serializable
	private List<Throwable> suppressedExceptions = SUPPRESSED_SENTINEL;

	/** Message for trying to suppress a null exception. */
	private static final String NULL_CAUSE_MESSAGE = "Cannot suppress a null exception.";

	/** Message for trying to suppress oneself. */
	private static final String SELF_SUPPRESSION_MESSAGE = "Self-suppression not permitted";

	/** Caption for labeling causative exception stack traces */
	private static final String CAUSE_CAPTION = "Caused by: ";

	/** Caption for labeling suppressed exception stack traces */
	private static final String SUPPRESSED_CAPTION = "Suppressed: ";

	/**
	* Constructs a new throwable with {@code null} as its detail message.
	* The cause is not initialized, and may subsequently be initialized by a
	* call to {@link #initCause}.
	*
	* <p>The {@link #fillInStackTrace()} method is called to initialize
	* the stack trace data in the newly created throwable.
	*/
	public Throwable() {
	fillInStackTrace();
	}

	/**
	* Constructs a new throwable with the specified detail message. The
	* cause is not initialized, and may subsequently be initialized by
	* a call to {@link #initCause}.
	*
	* <p>The {@link #fillInStackTrace()} method is called to initialize
	* the stack trace data in the newly created throwable.
	*
	* @param message the detail message. The detail message is saved for
	* later retrieval by the {@link #getMessage()} method.
	*/
	public Throwable(String message) {
	fillInStackTrace();
	detailMessage = message;
	}

	/**
	* Constructs a new throwable with the specified detail message and
	* cause. <p>Note that the detail message associated with
	* {@code cause} is <i>not</i> automatically incorporated in
	* this throwable's detail message.
	*
	* <p>The {@link #fillInStackTrace()} method is called to initialize
	* the stack trace data in the newly created throwable.
	*
	* @param message the detail message (which is saved for later retrieval
	* by the {@link #getMessage()} method).
	* @param cause the cause (which is saved for later retrieval by the
	* {@link #getCause()} method). (A {@code null} value is
	* permitted, and indicates that the cause is nonexistent or
	* unknown.)
	* @since 1.4
	*/
	public Throwable(String message, Throwable cause) {
	fillInStackTrace();
	detailMessage = message;
	this.cause = cause;
	}

	/**
	* Constructs a new throwable with the specified cause and a detail
	* message of {@code (cause==null ? null : cause.toString())} (which
	* typically contains the class and detail message of {@code cause}).
	* This constructor is useful for throwables that are little more than
	* wrappers for other throwables (for example, {@link
	* java.security.PrivilegedActionException}).
	*
	* <p>The {@link #fillInStackTrace()} method is called to initialize
	* the stack trace data in the newly created throwable.
	*
	* @param cause the cause (which is saved for later retrieval by the
	* {@link #getCause()} method). (A {@code null} value is
	* permitted, and indicates that the cause is nonexistent or
	* unknown.)
	* @since 1.4
	*/
	public Throwable(Throwable cause) {
	fillInStackTrace();
	detailMessage = (cause==null ? null : cause.toString());
	this.cause = cause;
	}

	/**
	* Constructs a new throwable with the specified detail message,
	* cause, {@linkplain #addSuppressed suppression} enabled or
	* disabled, and writable stack trace enabled or disabled. If
	* suppression is disabled, {@link #getSuppressed} for this object
	* will return a zero-length array and calls to {@link
	* #addSuppressed} that would otherwise append an exception to the
	* suppressed list will have no effect. If the writable stack
	* trace is false, this constructor will not call {@link
	* #fillInStackTrace()}, a {@code null} will be written to the
	* {@code stackTrace} field, and subsequent calls to {@code
	* fillInStackTrace} and {@link
	* #setStackTrace(StackTraceElement[])} will not set the stack
	* trace. If the writable stack trace is false, {@link
	* #getStackTrace} will return a zero length array.
	*
	* <p>Note that the other constructors of {@code Throwable} treat
	* suppression as being enabled and the stack trace as being
	* writable. Subclasses of {@code Throwable} should document any
	* conditions under which suppression is disabled and document
	* conditions under which the stack trace is not writable.
	* Disabling of suppression should only occur in exceptional
	* circumstances where special requirements exist, such as a
	* virtual machine reusing exception objects under low-memory
	* situations. Circumstances where a given exception object is
	* repeatedly caught and rethrown, such as to implement control
	* flow between two sub-systems, is another situation where
	* immutable throwable objects would be appropriate.
	*
	* @param message the detail message.
	* @param cause the cause. (A {@code null} value is permitted,
	* and indicates that the cause is nonexistent or unknown.)
	* @param enableSuppression whether or not suppression is enabled or disabled
	* @param writableStackTrace whether or not the stack trace should be
	* writable
	*
	* @see OutOfMemoryError
	* @see NullPointerException
	* @see ArithmeticException
	* @since 1.7
	*/
	protected Throwable(String message, Throwable cause,
	boolean enableSuppression,
	boolean writableStackTrace) {
	if (writableStackTrace) {
	fillInStackTrace();
	} else {
	stackTrace = null;
	}
	detailMessage = message;
	this.cause = cause;
	if (!enableSuppression)
	suppressedExceptions = null;
	}

	/**
	* Returns the detail message string of this throwable.
	*
	* @return the detail message string of this {@code Throwable} instance
	* (which may be {@code null}).
	*/
	public String getMessage() {
	return detailMessage;
	}

	/**
	* Creates a localized description of this throwable.
	* Subclasses may override this method in order to produce a
	* locale-specific message. For subclasses that do not override this
	* method, the default implementation returns the same result as
	* {@code getMessage()}.
	*
	* @return The localized description of this throwable.
	* @since 1.1
	*/
	public String getLocalizedMessage() {
	return getMessage();
	}

	/**
	* Returns the cause of this throwable or {@code null} if the
	* cause is nonexistent or unknown. (The cause is the throwable that
	* caused this throwable to get thrown.)
	*
	* <p>This implementation returns the cause that was supplied via one of
	* the constructors requiring a {@code Throwable}, or that was set after
	* creation with the {@link #initCause(Throwable)} method. While it is
	* typically unnecessary to override this method, a subclass can override
	* it to return a cause set by some other means. This is appropriate for
	* a "legacy chained throwable" that predates the addition of chained
	* exceptions to {@code Throwable}. Note that it is <i>not</i>
	* necessary to override any of the {@code PrintStackTrace} methods,
	* all of which invoke the {@code getCause} method to determine the
	* cause of a throwable.
	*
	* @return the cause of this throwable or {@code null} if the
	* cause is nonexistent or unknown.
	* @since 1.4
	*/
	public synchronized Throwable getCause() {
	return (cause==this ? null : cause);
	}

	/**
	* Initializes the <i>cause</i> of this throwable to the specified value.
	* (The cause is the throwable that caused this throwable to get thrown.)
	*
	* <p>This method can be called at most once. It is generally called from
	* within the constructor, or immediately after creating the
	* throwable. If this throwable was created
	* with {@link #Throwable(Throwable)} or
	* {@link #Throwable(String,Throwable)}, this method cannot be called
	* even once.
	*
	* <p>An example of using this method on a legacy throwable type
	* without other support for setting the cause is:
	*
	* <pre>
	* try {
	* lowLevelOp();
	* } catch (LowLevelException le) {
	* throw (HighLevelException)
	* new HighLevelException().initCause(le); // Legacy constructor
	* }
	* </pre>
	*
	* @param cause the cause (which is saved for later retrieval by the
	* {@link #getCause()} method). (A {@code null} value is
	* permitted, and indicates that the cause is nonexistent or
	* unknown.)
	* @return a reference to this {@code Throwable} instance.
	* @throws IllegalArgumentException if {@code cause} is this
	* throwable. (A throwable cannot be its own cause.)
	* @throws IllegalStateException if this throwable was
	* created with {@link #Throwable(Throwable)} or
	* {@link #Throwable(String,Throwable)}, or this method has already
	* been called on this throwable.
	* @since 1.4
	*/
	public synchronized Throwable initCause(Throwable cause) {
	if (this.cause != this)
	throw new IllegalStateException("Can't overwrite cause with " +
	Objects.toString(cause, "a null"), this);
	if (cause == this)
	throw new IllegalArgumentException("Self-causation not permitted", this);
	this.cause = cause;
	return this;
	}

	/*
	* This is called by readObject of a few exceptions such as
	* ClassNotFoundException and ExceptionInInitializerError to deserialize
	* a stream output from an older runtime version where the cause may
	* have set to null.
	*/
	final void setCause(Throwable t) {
	this.cause = t;
	}

	/**
	* Returns a short description of this throwable.
	* The result is the concatenation of:
	* <ul>
	* <li> the {@linkplain Class#getName() name} of the class of this object
	* <li> ": " (a colon and a space)
	* <li> the result of invoking this object's {@link #getLocalizedMessage}
	* method
	* </ul>
	* If {@code getLocalizedMessage} returns {@code null}, then just
	* the class name is returned.
	*
	* @return a string representation of this throwable.
	*/
	public String toString() {
	String s = getClass().getName();
	String message = getLocalizedMessage();
	return (message != null) ? (s + ": " + message) : s;
	}

	/**
	* Prints this throwable and its backtrace to the
	* standard error stream. This method prints a stack trace for this
	* {@code Throwable} object on the error output stream that is
	* the value of the field {@code System.err}. The first line of
	* output contains the result of the {@link #toString()} method for
	* this object. Remaining lines represent data previously recorded by
	* the method {@link #fillInStackTrace()}. The format of this
	* information depends on the implementation, but the following
	* example may be regarded as typical:
	* <blockquote><pre>
	* java.lang.NullPointerException
	* at MyClass.mash(MyClass.java:9)
	* at MyClass.crunch(MyClass.java:6)
	* at MyClass.main(MyClass.java:3)
	* </pre></blockquote>
	* This example was produced by running the program:
	* <pre>
	* class MyClass {
	* public static void main(String[] args) {
	* crunch(null);
	* }
	* static void crunch(int[] a) {
	* mash(a);
	* }
	* static void mash(int[] b) {
	* System.out.println(b[0]);
	* }
	* }
	* </pre>
	* The backtrace for a throwable with an initialized, non-null cause
	* should generally include the backtrace for the cause. The format
	* of this information depends on the implementation, but the following
	* example may be regarded as typical:
	* <pre>
	* HighLevelException: MidLevelException: LowLevelException
	* at Junk.a(Junk.java:13)
	* at Junk.main(Junk.java:4)
	* Caused by: MidLevelException: LowLevelException
	* at Junk.c(Junk.java:23)
	* at Junk.b(Junk.java:17)
	* at Junk.a(Junk.java:11)
	* ... 1 more
	* Caused by: LowLevelException
	* at Junk.e(Junk.java:30)
	* at Junk.d(Junk.java:27)
	* at Junk.c(Junk.java:21)
	* ... 3 more
	* </pre>
	* Note the presence of lines containing the characters {@code "..."}.
	* These lines indicate that the remainder of the stack trace for this
	* exception matches the indicated number of frames from the bottom of the
	* stack trace of the exception that was caused by this exception (the
	* "enclosing" exception). This shorthand can greatly reduce the length
	* of the output in the common case where a wrapped exception is thrown
	* from same method as the "causative exception" is caught. The above
	* example was produced by running the program:
	* <pre>
	* public class Junk {
	* public static void main(String args[]) {
	* try {
	* a();
	* } catch(HighLevelException e) {
	* e.printStackTrace();
	* }
	* }
	* static void a() throws HighLevelException {
	* try {
	* b();
	* } catch(MidLevelException e) {
	* throw new HighLevelException(e);
	* }
	* }
	* static void b() throws MidLevelException {
	* c();
	* }
	* static void c() throws MidLevelException {
	* try {
	* d();
	* } catch(LowLevelException e) {
	* throw new MidLevelException(e);
	* }
	* }
	* static void d() throws LowLevelException {
	* e();
	* }
	* static void e() throws LowLevelException {
	* throw new LowLevelException();
	* }
	* }
	*
	* class HighLevelException extends Exception {
	* HighLevelException(Throwable cause) { super(cause); }
	* }
	*
	* class MidLevelException extends Exception {
	* MidLevelException(Throwable cause) { super(cause); }
	* }
	*
	* class LowLevelException extends Exception {
	* }
	* </pre>
	* As of release 7, the platform supports the notion of
	* <i>suppressed exceptions</i> (in conjunction with the {@code
	* try}-with-resources statement). Any exceptions that were
	* suppressed in order to deliver an exception are printed out
	* beneath the stack trace. The format of this information
	* depends on the implementation, but the following example may be
	* regarded as typical:
	*
	* <pre>
	* Exception in thread "main" java.lang.Exception: Something happened
	* at Foo.bar(Foo.java:10)
	* at Foo.main(Foo.java:5)
	* Suppressed: Resource$CloseFailException: Resource ID = 0
	* at Resource.close(Resource.java:26)
	* at Foo.bar(Foo.java:9)
	* ... 1 more
	* </pre>
	* Note that the "... n more" notation is used on suppressed exceptions
	* just as it is used on causes. Unlike causes, suppressed exceptions are
	* indented beyond their "containing exceptions."
	*
	* <p>An exception can have both a cause and one or more suppressed
	* exceptions:
	* <pre>
	* Exception in thread "main" java.lang.Exception: Main block
	* at Foo3.main(Foo3.java:7)
	* Suppressed: Resource$CloseFailException: Resource ID = 2
	* at Resource.close(Resource.java:26)
	* at Foo3.main(Foo3.java:5)
	* Suppressed: Resource$CloseFailException: Resource ID = 1
	* at Resource.close(Resource.java:26)
	* at Foo3.main(Foo3.java:5)
	* Caused by: java.lang.Exception: I did it
	* at Foo3.main(Foo3.java:8)
	* </pre>
	* Likewise, a suppressed exception can have a cause:
	* <pre>
	* Exception in thread "main" java.lang.Exception: Main block
	* at Foo4.main(Foo4.java:6)
	* Suppressed: Resource2$CloseFailException: Resource ID = 1
	* at Resource2.close(Resource2.java:20)
	* at Foo4.main(Foo4.java:5)
	* Caused by: java.lang.Exception: Rats, you caught me
	* at Resource2$CloseFailException.<init>(Resource2.java:45)
	* ... 2 more
	* </pre>
	*/
	public void printStackTrace() {
	printStackTrace(System.err);
	}

	/**
	* Prints this throwable and its backtrace to the specified print stream.
	*
	* @param s {@code PrintStream} to use for output
	*/
	public void printStackTrace(PrintStream s) {
	printStackTrace(new WrappedPrintStream(s));
	}

	private void printStackTrace(PrintStreamOrWriter s) {
	// Guard against malicious overrides of Throwable.equals by
	// using a Set with identity equality semantics.
	Set<Throwable> dejaVu = Collections.newSetFromMap(new IdentityHashMap<>());
	dejaVu.add(this);

	synchronized (s.lock()) {
	// Print our stack trace
	s.println(this);
	StackTraceElement[] trace = getOurStackTrace();
	for (StackTraceElement traceElement : trace)
	s.println("\tat " + traceElement);

	// Print suppressed exceptions, if any
	for (Throwable se : getSuppressed())
	se.printEnclosedStackTrace(s, trace, SUPPRESSED_CAPTION, "\t", dejaVu);

	// Print cause, if any
	Throwable ourCause = getCause();
	if (ourCause != null)
	ourCause.printEnclosedStackTrace(s, trace, CAUSE_CAPTION, "", dejaVu);
	}
	}

	/**
	* Print our stack trace as an enclosed exception for the specified
	* stack trace.
	*/
	private void printEnclosedStackTrace(PrintStreamOrWriter s,
	StackTraceElement[] enclosingTrace,
	String caption,
	String prefix,
	Set<Throwable> dejaVu) {
	assert Thread.holdsLock(s.lock());
	if (dejaVu.contains(this)) {
	s.println(prefix + caption + "[CIRCULAR REFERENCE: " + this + "]");
	} else {
	dejaVu.add(this);
	// Compute number of frames in common between this and enclosing trace
	StackTraceElement[] trace = getOurStackTrace();
	int m = trace.length - 1;
	int n = enclosingTrace.length - 1;
	while (m >= 0 && n >=0 && trace[m].equals(enclosingTrace[n])) {
	m--; n--;
	}
	int framesInCommon = trace.length - 1 - m;

	// Print our stack trace
	s.println(prefix + caption + this);
	for (int i = 0; i <= m; i++)
	s.println(prefix + "\tat " + trace[i]);
	if (framesInCommon != 0)
	s.println(prefix + "\t... " + framesInCommon + " more");

	// Print suppressed exceptions, if any
	for (Throwable se : getSuppressed())
	se.printEnclosedStackTrace(s, trace, SUPPRESSED_CAPTION,
	prefix +"\t", dejaVu);

	// Print cause, if any
	Throwable ourCause = getCause();
	if (ourCause != null)
	ourCause.printEnclosedStackTrace(s, trace, CAUSE_CAPTION, prefix, dejaVu);
	}
	}

	/**
	* Prints this throwable and its backtrace to the specified
	* print writer.
	*
	* @param s {@code PrintWriter} to use for output
	* @since 1.1
	*/
	public void printStackTrace(PrintWriter s) {
	printStackTrace(new WrappedPrintWriter(s));
	}

	/**
	* Wrapper class for PrintStream and PrintWriter to enable a single
	* implementation of printStackTrace.
	*/
	private abstract static class PrintStreamOrWriter {
	/** Returns the object to be locked when using this StreamOrWriter */
	abstract Object lock();

	/** Prints the specified string as a line on this StreamOrWriter */
	abstract void println(Object o);
	}

	private static class WrappedPrintStream extends PrintStreamOrWriter {
	private final PrintStream printStream;

	WrappedPrintStream(PrintStream printStream) {
	this.printStream = printStream;
	}

	Object lock() {
	return printStream;
	}

	void println(Object o) {
	printStream.println(o);
	}
	}

	private static class WrappedPrintWriter extends PrintStreamOrWriter {
	private final PrintWriter printWriter;

	WrappedPrintWriter(PrintWriter printWriter) {
	this.printWriter = printWriter;
	}

	Object lock() {
	return printWriter;
	}

	void println(Object o) {
	printWriter.println(o);
	}
	}

	/**
	* Fills in the execution stack trace. This method records within this
	* {@code Throwable} object information about the current state of
	* the stack frames for the current thread.
	*
	* <p>If the stack trace of this {@code Throwable} {@linkplain
	* Throwable#Throwable(String, Throwable, boolean, boolean) is not
	* writable}, calling this method has no effect.
	*
	* @return a reference to this {@code Throwable} instance.
	* @see java.lang.Throwable#printStackTrace()
	*/
	public synchronized Throwable fillInStackTrace() {
	if (stackTrace != null \|\|
	backtrace != null /* Out of protocol state */ ) {
	fillInStackTrace(0);
	stackTrace = UNASSIGNED_STACK;
	}
	return this;
	}

	private native Throwable fillInStackTrace(int dummy);

	/**
	* Provides programmatic access to the stack trace information printed by
	* {@link #printStackTrace()}. Returns an array of stack trace elements,
	* each representing one stack frame. The zeroth element of the array
	* (assuming the array's length is non-zero) represents the top of the
	* stack, which is the last method invocation in the sequence. Typically,
	* this is the point at which this throwable was created and thrown.
	* The last element of the array (assuming the array's length is non-zero)
	* represents the bottom of the stack, which is the first method invocation
	* in the sequence.
	*
	* <p>Some virtual machines may, under some circumstances, omit one
	* or more stack frames from the stack trace. In the extreme case,
	* a virtual machine that has no stack trace information concerning
	* this throwable is permitted to return a zero-length array from this
	* method. Generally speaking, the array returned by this method will
	* contain one element for every frame that would be printed by
	* {@code printStackTrace}. Writes to the returned array do not
	* affect future calls to this method.
	*
	* @return an array of stack trace elements representing the stack trace
	* pertaining to this throwable.
	* @since 1.4
	*/
	public StackTraceElement[] getStackTrace() {
	return getOurStackTrace().clone();
	}

	private synchronized StackTraceElement[] getOurStackTrace() {
	// Initialize stack trace field with information from
	// backtrace if this is the first call to this method
	if (stackTrace == UNASSIGNED_STACK \|\|
	(stackTrace == null && backtrace != null) /* Out of protocol state */) {
	stackTrace = StackTraceElement.of(this, depth);
	} else if (stackTrace == null) {
	return UNASSIGNED_STACK;
	}
	return stackTrace;
	}

	/**
	* Sets the stack trace elements that will be returned by
	* {@link #getStackTrace()} and printed by {@link #printStackTrace()}
	* and related methods.
	*
	* This method, which is designed for use by RPC frameworks and other
	* advanced systems, allows the client to override the default
	* stack trace that is either generated by {@link #fillInStackTrace()}
	* when a throwable is constructed or deserialized when a throwable is
	* read from a serialization stream.
	*
	* <p>If the stack trace of this {@code Throwable} {@linkplain
	* Throwable#Throwable(String, Throwable, boolean, boolean) is not
	* writable}, calling this method has no effect other than
	* validating its argument.
	*
	* @param stackTrace the stack trace elements to be associated with
	* this {@code Throwable}. The specified array is copied by this
	* call; changes in the specified array after the method invocation
	* returns will have no affect on this {@code Throwable}'s stack
	* trace.
	*
	* @throws NullPointerException if {@code stackTrace} is
	* {@code null} or if any of the elements of
	* {@code stackTrace} are {@code null}
	*
	* @since 1.4
	*/
	public void setStackTrace(StackTraceElement[] stackTrace) {
	// Validate argument
	StackTraceElement[] defensiveCopy = stackTrace.clone();
	for (int i = 0; i < defensiveCopy.length; i++) {
	if (defensiveCopy[i] == null)
	throw new NullPointerException("stackTrace[" + i + "]");
	}

	synchronized (this) {
	if (this.stackTrace == null && // Immutable stack
	backtrace == null) // Test for out of protocol state
	return;
	this.stackTrace = defensiveCopy;
	}
	}

	/**
	* Reads a {@code Throwable} from a stream, enforcing
	* well-formedness constraints on fields. Null entries and
	* self-pointers are not allowed in the list of {@code
	* suppressedExceptions}. Null entries are not allowed for stack
	* trace elements. A null stack trace in the serial form results
	* in a zero-length stack element array. A single-element stack
	* trace whose entry is equal to {@code new StackTraceElement("",
	* "", null, Integer.MIN_VALUE)} results in a {@code null} {@code
	* stackTrace} field.
	*
	* Note that there are no constraints on the value the {@code
	* cause} field can hold; both {@code null} and {@code this} are
	* valid values for the field.
	*
	* @param s the {@code ObjectInputStream} from which data is read
	* @throws IOException if an I/O error occurs
	* @throws ClassNotFoundException if a serialized class cannot be loaded
	*/
	@java.io.Serial
	private void readObject(ObjectInputStream s)
	throws IOException, ClassNotFoundException {
	s.defaultReadObject(); // read in all fields

	// Set suppressed exceptions and stack trace elements fields
	// to marker values until the contents from the serial stream
	// are validated.
	List<Throwable> candidateSuppressedExceptions = suppressedExceptions;
	suppressedExceptions = SUPPRESSED_SENTINEL;

	StackTraceElement[] candidateStackTrace = stackTrace;
	stackTrace = UNASSIGNED_STACK.clone();

	if (candidateSuppressedExceptions != null) {
	int suppressedSize = validateSuppressedExceptionsList(candidateSuppressedExceptions);
	if (suppressedSize > 0) { // Copy valid Throwables to new list
	var suppList = new ArrayList<Throwable>(Math.min(100, suppressedSize));

	for (Throwable t : candidateSuppressedExceptions) {
	// Enforce constraints on suppressed exceptions in
	// case of corrupt or malicious stream.
	Objects.requireNonNull(t, NULL_CAUSE_MESSAGE);
	if (t == this)
	throw new IllegalArgumentException(SELF_SUPPRESSION_MESSAGE);
	suppList.add(t);
	}
	// If there are any invalid suppressed exceptions,
	// implicitly use the sentinel value assigned earlier.
	suppressedExceptions = suppList;
	}
	} else {
	suppressedExceptions = null;
	}

	/*
	* For zero-length stack traces, use a clone of
	* UNASSIGNED_STACK rather than UNASSIGNED_STACK itself to
	* allow identity comparison against UNASSIGNED_STACK in
	* getOurStackTrace. The identity of UNASSIGNED_STACK in
	* stackTrace indicates to the getOurStackTrace method that
	* the stackTrace needs to be constructed from the information
	* in backtrace.
	*/
	if (candidateStackTrace != null) {
	// Work from a clone of the candidateStackTrace to ensure
	// consistency of checks.
	candidateStackTrace = candidateStackTrace.clone();
	if (candidateStackTrace.length >= 1) {
	if (candidateStackTrace.length == 1 &&
	// Check for the marker of an immutable stack trace
	SentinelHolder.STACK_TRACE_ELEMENT_SENTINEL.equals(candidateStackTrace[0])) {
	stackTrace = null;
	} else { // Verify stack trace elements are non-null.
	for (StackTraceElement ste : candidateStackTrace) {
	Objects.requireNonNull(ste, "null StackTraceElement in serial stream.");
	}
	stackTrace = candidateStackTrace;
	}
	}
	}
	// A null stackTrace field in the serial form can result from
	// an exception serialized without that field in older JDK
	// releases; treat such exceptions as having empty stack
	// traces by leaving stackTrace assigned to a clone of
	// UNASSIGNED_STACK.
	}

	private int validateSuppressedExceptionsList(List<Throwable> deserSuppressedExceptions)
	throws IOException {
	if (!Object.class.getModule().
	equals(deserSuppressedExceptions.getClass().getModule())) {
	throw new StreamCorruptedException("List implementation not in base module.");
	} else {
	int size = deserSuppressedExceptions.size();
	if (size < 0) {
	throw new StreamCorruptedException("Negative list size reported.");
	}
	return size;
	}
	}

	/**
	* Write a {@code Throwable} object to a stream.
	*
	* A {@code null} stack trace field is represented in the serial
	* form as a one-element array whose element is equal to {@code
	* new StackTraceElement("", "", null, Integer.MIN_VALUE)}.
	*
	* @param s the {@code ObjectOutputStream} to which data is written
	* @throws IOException if an I/O error occurs
	*/
	@java.io.Serial
	private synchronized void writeObject(ObjectOutputStream s)
	throws IOException {
	// Ensure that the stackTrace field is initialized to a
	// non-null value, if appropriate. As of JDK 7, a null stack
	// trace field is a valid value indicating the stack trace
	// should not be set.
	getOurStackTrace();

	StackTraceElement[] oldStackTrace = stackTrace;
	try {
	if (stackTrace == null)
	stackTrace = SentinelHolder.STACK_TRACE_SENTINEL;
	s.defaultWriteObject();
	} finally {
	stackTrace = oldStackTrace;
	}
	}

	/**
	* Appends the specified exception to the exceptions that were
	* suppressed in order to deliver this exception. This method is
	* thread-safe and typically called (automatically and implicitly)
	* by the {@code try}-with-resources statement.
	*
	* <p>The suppression behavior is enabled <em>unless</em> disabled
	* {@linkplain #Throwable(String, Throwable, boolean, boolean) via
	* a constructor}. When suppression is disabled, this method does
	* nothing other than to validate its argument.
	*
	* <p>Note that when one exception {@linkplain
	* #initCause(Throwable) causes} another exception, the first
	* exception is usually caught and then the second exception is
	* thrown in response. In other words, there is a causal
	* connection between the two exceptions.
	*
	* In contrast, there are situations where two independent
	* exceptions can be thrown in sibling code blocks, in particular
	* in the {@code try} block of a {@code try}-with-resources
	* statement and the compiler-generated {@code finally} block
	* which closes the resource.
	*
	* In these situations, only one of the thrown exceptions can be
	* propagated. In the {@code try}-with-resources statement, when
	* there are two such exceptions, the exception originating from
	* the {@code try} block is propagated and the exception from the
	* {@code finally} block is added to the list of exceptions
	* suppressed by the exception from the {@code try} block. As an
	* exception unwinds the stack, it can accumulate multiple
	* suppressed exceptions.
	*
	* <p>An exception may have suppressed exceptions while also being
	* caused by another exception. Whether or not an exception has a
	* cause is semantically known at the time of its creation, unlike
	* whether or not an exception will suppress other exceptions
	* which is typically only determined after an exception is
	* thrown.
	*
	* <p>Note that programmer written code is also able to take
	* advantage of calling this method in situations where there are
	* multiple sibling exceptions and only one can be propagated.
	*
	* @param exception the exception to be added to the list of
	* suppressed exceptions
	* @throws IllegalArgumentException if {@code exception} is this
	* throwable; a throwable cannot suppress itself.
	* @throws NullPointerException if {@code exception} is {@code null}
	* @since 1.7
	*/
	public final synchronized void addSuppressed(Throwable exception) {
	if (exception == this)
	throw new IllegalArgumentException(SELF_SUPPRESSION_MESSAGE, exception);

	Objects.requireNonNull(exception, NULL_CAUSE_MESSAGE);

	if (suppressedExceptions == null) // Suppressed exceptions not recorded
	return;

	if (suppressedExceptions == SUPPRESSED_SENTINEL)
	suppressedExceptions = new ArrayList<>(1);

	suppressedExceptions.add(exception);
	}

	private static final Throwable[] EMPTY_THROWABLE_ARRAY = new Throwable[0];

	/**
	* Returns an array containing all of the exceptions that were
	* suppressed, typically by the {@code try}-with-resources
	* statement, in order to deliver this exception.
	*
	* If no exceptions were suppressed or {@linkplain
	* #Throwable(String, Throwable, boolean, boolean) suppression is
	* disabled}, an empty array is returned. This method is
	* thread-safe. Writes to the returned array do not affect future
	* calls to this method.
	*
	* @return an array containing all of the exceptions that were
	* suppressed to deliver this exception.
	* @since 1.7
	*/
	public final synchronized Throwable[] getSuppressed() {
	if (suppressedExceptions == SUPPRESSED_SENTINEL \|\|
	suppressedExceptions == null)
	return EMPTY_THROWABLE_ARRAY;
	else
	return suppressedExceptions.toArray(EMPTY_THROWABLE_ARRAY);
	}
	}

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