/*
* Copyright (c) 1994, 2016, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
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*/
package java.lang;
import java.lang.ref.
Reference;
import java.lang.ref.
ReferenceQueue;
import java.lang.ref.
WeakReference;
import java.security.
AccessController;
import java.security.
AccessControlContext;
import java.security.
PrivilegedAction;
import java.util.
Map;
import java.util.
HashMap;
import java.util.concurrent.
ConcurrentHashMap;
import java.util.concurrent.
ConcurrentMap;
import java.util.concurrent.locks.
LockSupport;
import sun.nio.ch.
Interruptible;
import sun.reflect.
CallerSensitive;
import sun.reflect.
Reflection;
import sun.security.util.
SecurityConstants;
/**
* A <i>thread</i> is a thread of execution in a program. The Java
* Virtual Machine allows an application to have multiple threads of
* execution running concurrently.
* <p>
* Every thread has a priority. Threads with higher priority are
* executed in preference to threads with lower priority. Each thread
* may or may not also be marked as a daemon. When code running in
* some thread creates a new <code>Thread</code> object, the new
* thread has its priority initially set equal to the priority of the
* creating thread, and is a daemon thread if and only if the
* creating thread is a daemon.
* <p>
* When a Java Virtual Machine starts up, there is usually a single
* non-daemon thread (which typically calls the method named
* <code>main</code> of some designated class). The Java Virtual
* Machine continues to execute threads until either of the following
* occurs:
* <ul>
* <li>The <code>exit</code> method of class <code>Runtime</code> has been
* called and the security manager has permitted the exit operation
* to take place.
* <li>All threads that are not daemon threads have died, either by
* returning from the call to the <code>run</code> method or by
* throwing an exception that propagates beyond the <code>run</code>
* method.
* </ul>
* <p>
* There are two ways to create a new thread of execution. One is to
* declare a class to be a subclass of <code>Thread</code>. This
* subclass should override the <code>run</code> method of class
* <code>Thread</code>. An instance of the subclass can then be
* allocated and started. For example, a thread that computes primes
* larger than a stated value could be written as follows:
* <hr><blockquote><pre>
* class PrimeThread extends Thread {
* long minPrime;
* PrimeThread(long minPrime) {
* this.minPrime = minPrime;
* }
*
* public void run() {
* // compute primes larger than minPrime
* . . .
* }
* }
* </pre></blockquote><hr>
* <p>
* The following code would then create a thread and start it running:
* <blockquote><pre>
* PrimeThread p = new PrimeThread(143);
* p.start();
* </pre></blockquote>
* <p>
* The other way to create a thread is to declare a class that
* implements the <code>Runnable</code> interface. That class then
* implements the <code>run</code> method. An instance of the class can
* then be allocated, passed as an argument when creating
* <code>Thread</code>, and started. The same example in this other
* style looks like the following:
* <hr><blockquote><pre>
* class PrimeRun implements Runnable {
* long minPrime;
* PrimeRun(long minPrime) {
* this.minPrime = minPrime;
* }
*
* public void run() {
* // compute primes larger than minPrime
* . . .
* }
* }
* </pre></blockquote><hr>
* <p>
* The following code would then create a thread and start it running:
* <blockquote><pre>
* PrimeRun p = new PrimeRun(143);
* new Thread(p).start();
* </pre></blockquote>
* <p>
* Every thread has a name for identification purposes. More than
* one thread may have the same name. If a name is not specified when
* a thread is created, a new name is generated for it.
* <p>
* Unless otherwise noted, passing a {@code null} argument to a constructor
* or method in this class will cause a {@link NullPointerException} to be
* thrown.
*
* @author unascribed
* @see Runnable
* @see Runtime#exit(int)
* @see #run()
* @see #stop()
* @since JDK1.0
*/
public
class
Thread implements
Runnable {
/* Make sure registerNatives is the first thing <clinit> does. */
private static native void
registerNatives();
static {
registerNatives();
}
private volatile
String name;
private int
priority;
private
Thread threadQ;
private long
eetop;
/* Whether or not to single_step this thread. */
private boolean
single_step;
/* Whether or not the thread is a daemon thread. */
private boolean
daemon = false;
/* JVM state */
private boolean
stillborn = false;
/* What will be run. */
private
Runnable target;
/* The group of this thread */
private
ThreadGroup group;
/* The context ClassLoader for this thread */
private
ClassLoader contextClassLoader;
/* The inherited AccessControlContext of this thread */
private
AccessControlContext inheritedAccessControlContext;
/* For autonumbering anonymous threads. */
private static int
threadInitNumber;
private static synchronized int
nextThreadNum() {
return
threadInitNumber++;
}
/* ThreadLocal values pertaining to this thread. This map is maintained
* by the ThreadLocal class. */
ThreadLocal.
ThreadLocalMap threadLocals = null;
/*
* InheritableThreadLocal values pertaining to this thread. This map is
* maintained by the InheritableThreadLocal class.
*/
ThreadLocal.
ThreadLocalMap inheritableThreadLocals = null;
/*
* The requested stack size for this thread, or 0 if the creator did
* not specify a stack size. It is up to the VM to do whatever it
* likes with this number; some VMs will ignore it.
*/
private long
stackSize;
/*
* JVM-private state that persists after native thread termination.
*/
private long
nativeParkEventPointer;
/*
* Thread ID
*/
private long
tid;
/* For generating thread ID */
private static long
threadSeqNumber;
/* Java thread status for tools,
* initialized to indicate thread 'not yet started'
*/
private volatile int
threadStatus = 0;
private static synchronized long
nextThreadID() {
return ++
threadSeqNumber;
}
/**
* The argument supplied to the current call to
* java.util.concurrent.locks.LockSupport.park.
* Set by (private) java.util.concurrent.locks.LockSupport.setBlocker
* Accessed using java.util.concurrent.locks.LockSupport.getBlocker
*/
volatile
Object parkBlocker;
/* The object in which this thread is blocked in an interruptible I/O
* operation, if any. The blocker's interrupt method should be invoked
* after setting this thread's interrupt status.
*/
private volatile
Interruptible blocker;
private final
Object blockerLock = new
Object();
/* Set the blocker field; invoked via sun.misc.SharedSecrets from java.nio code
*/
void
blockedOn(
Interruptible b) {
synchronized (
blockerLock) {
blocker =
b;
}
}
/**
* The minimum priority that a thread can have.
*/
public final static int
MIN_PRIORITY = 1;
/**
* The default priority that is assigned to a thread.
*/
public final static int
NORM_PRIORITY = 5;
/**
* The maximum priority that a thread can have.
*/
public final static int
MAX_PRIORITY = 10;
/**
* Returns a reference to the currently executing thread object.
*
* @return the currently executing thread.
*/
public static native
Thread currentThread();
/**
* A hint to the scheduler that the current thread is willing to yield
* its current use of a processor. The scheduler is free to ignore this
* hint.
*
* <p> Yield is a heuristic attempt to improve relative progression
* between threads that would otherwise over-utilise a CPU. Its use
* should be combined with detailed profiling and benchmarking to
* ensure that it actually has the desired effect.
*
* <p> It is rarely appropriate to use this method. It may be useful
* for debugging or testing purposes, where it may help to reproduce
* bugs due to race conditions. It may also be useful when designing
* concurrency control constructs such as the ones in the
* {@link java.util.concurrent.locks} package.
*/
public static native void
yield();
/**
* Causes the currently executing thread to sleep (temporarily cease
* execution) for the specified number of milliseconds, subject to
* the precision and accuracy of system timers and schedulers. The thread
* does not lose ownership of any monitors.
*
* @param millis
* the length of time to sleep in milliseconds
*
* @throws IllegalArgumentException
* if the value of {@code millis} is negative
*
* @throws InterruptedException
* if any thread has interrupted the current thread. The
* <i>interrupted status</i> of the current thread is
* cleared when this exception is thrown.
*/
public static native void
sleep(long
millis) throws
InterruptedException;
/**
* Causes the currently executing thread to sleep (temporarily cease
* execution) for the specified number of milliseconds plus the specified
* number of nanoseconds, subject to the precision and accuracy of system
* timers and schedulers. The thread does not lose ownership of any
* monitors.
*
* @param millis
* the length of time to sleep in milliseconds
*
* @param nanos
* {@code 0-999999} additional nanoseconds to sleep
*
* @throws IllegalArgumentException
* if the value of {@code millis} is negative, or the value of
* {@code nanos} is not in the range {@code 0-999999}
*
* @throws InterruptedException
* if any thread has interrupted the current thread. The
* <i>interrupted status</i> of the current thread is
* cleared when this exception is thrown.
*/
public static void
sleep(long
millis, int
nanos)
throws
InterruptedException {
if (
millis < 0) {
throw new
IllegalArgumentException("timeout value is negative");
}
if (
nanos < 0 ||
nanos > 999999) {
throw new
IllegalArgumentException(
"nanosecond timeout value out of range");
}
if (
nanos >= 500000 || (
nanos != 0 &&
millis == 0)) {
millis++;
}
sleep(
millis);
}
/**
* Initializes a Thread with the current AccessControlContext.
* @see #init(ThreadGroup,Runnable,String,long,AccessControlContext,boolean)
*/
private void
init(
ThreadGroup g,
Runnable target,
String name,
long
stackSize) {
init(
g,
target,
name,
stackSize, null, true);
}
/**
* Initializes a Thread.
*
* @param g the Thread group
* @param target the object whose run() method gets called
* @param name the name of the new Thread
* @param stackSize the desired stack size for the new thread, or
* zero to indicate that this parameter is to be ignored.
* @param acc the AccessControlContext to inherit, or
* AccessController.getContext() if null
* @param inheritThreadLocals if {@code true}, inherit initial values for
* inheritable thread-locals from the constructing thread
*/
private void
init(
ThreadGroup g,
Runnable target,
String name,
long
stackSize,
AccessControlContext acc,
boolean
inheritThreadLocals) {
if (
name == null) {
throw new
NullPointerException("name cannot be null");
}
this.
name =
name;
Thread parent =
currentThread();
SecurityManager security =
System.
getSecurityManager();
if (
g == null) {
/* Determine if it's an applet or not */
/* If there is a security manager, ask the security manager
what to do. */
if (
security != null) {
g =
security.
getThreadGroup();
}
/* If the security doesn't have a strong opinion of the matter
use the parent thread group. */
if (
g == null) {
g =
parent.
getThreadGroup();
}
}
/* checkAccess regardless of whether or not threadgroup is
explicitly passed in. */
g.
checkAccess();
/*
* Do we have the required permissions?
*/
if (
security != null) {
if (
isCCLOverridden(
getClass())) {
security.
checkPermission(
SUBCLASS_IMPLEMENTATION_PERMISSION);
}
}
g.
addUnstarted();
this.
group =
g;
this.
daemon =
parent.
isDaemon();
this.
priority =
parent.
getPriority();
if (
security == null ||
isCCLOverridden(
parent.
getClass()))
this.
contextClassLoader =
parent.
getContextClassLoader();
else
this.
contextClassLoader =
parent.
contextClassLoader;
this.
inheritedAccessControlContext =
acc != null ?
acc :
AccessController.
getContext();
this.
target =
target;
setPriority(
priority);
if (
inheritThreadLocals &&
parent.
inheritableThreadLocals != null)
this.
inheritableThreadLocals =
ThreadLocal.
createInheritedMap(
parent.
inheritableThreadLocals);
/* Stash the specified stack size in case the VM cares */
this.
stackSize =
stackSize;
/* Set thread ID */
tid =
nextThreadID();
}
/**
* Throws CloneNotSupportedException as a Thread can not be meaningfully
* cloned. Construct a new Thread instead.
*
* @throws CloneNotSupportedException
* always
*/
@
Override
protected
Object clone() throws
CloneNotSupportedException {
throw new
CloneNotSupportedException();
}
/**
* Allocates a new {@code Thread} object. This constructor has the same
* effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
* {@code (null, null, gname)}, where {@code gname} is a newly generated
* name. Automatically generated names are of the form
* {@code "Thread-"+}<i>n</i>, where <i>n</i> is an integer.
*/
public
Thread() {
init(null, null, "Thread-" +
nextThreadNum(), 0);
}
/**
* Allocates a new {@code Thread} object. This constructor has the same
* effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
* {@code (null, target, gname)}, where {@code gname} is a newly generated
* name. Automatically generated names are of the form
* {@code "Thread-"+}<i>n</i>, where <i>n</i> is an integer.
*
* @param target
* the object whose {@code run} method is invoked when this thread
* is started. If {@code null}, this classes {@code run} method does
* nothing.
*/
public
Thread(
Runnable target) {
init(null,
target, "Thread-" +
nextThreadNum(), 0);
}
/**
* Creates a new Thread that inherits the given AccessControlContext.
* This is not a public constructor.
*/
Thread(
Runnable target,
AccessControlContext acc) {
init(null,
target, "Thread-" +
nextThreadNum(), 0,
acc, false);
}
/**
* Allocates a new {@code Thread} object. This constructor has the same
* effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
* {@code (group, target, gname)} ,where {@code gname} is a newly generated
* name. Automatically generated names are of the form
* {@code "Thread-"+}<i>n</i>, where <i>n</i> is an integer.
*
* @param group
* the thread group. If {@code null} and there is a security
* manager, the group is determined by {@linkplain
* SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
* If there is not a security manager or {@code
* SecurityManager.getThreadGroup()} returns {@code null}, the group
* is set to the current thread's thread group.
*
* @param target
* the object whose {@code run} method is invoked when this thread
* is started. If {@code null}, this thread's run method is invoked.
*
* @throws SecurityException
* if the current thread cannot create a thread in the specified
* thread group
*/
public
Thread(
ThreadGroup group,
Runnable target) {
init(
group,
target, "Thread-" +
nextThreadNum(), 0);
}
/**
* Allocates a new {@code Thread} object. This constructor has the same
* effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
* {@code (null, null, name)}.
*
* @param name
* the name of the new thread
*/
public
Thread(
String name) {
init(null, null,
name, 0);
}
/**
* Allocates a new {@code Thread} object. This constructor has the same
* effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
* {@code (group, null, name)}.
*
* @param group
* the thread group. If {@code null} and there is a security
* manager, the group is determined by {@linkplain
* SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
* If there is not a security manager or {@code
* SecurityManager.getThreadGroup()} returns {@code null}, the group
* is set to the current thread's thread group.
*
* @param name
* the name of the new thread
*
* @throws SecurityException
* if the current thread cannot create a thread in the specified
* thread group
*/
public
Thread(
ThreadGroup group,
String name) {
init(
group, null,
name, 0);
}
/**
* Allocates a new {@code Thread} object. This constructor has the same
* effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
* {@code (null, target, name)}.
*
* @param target
* the object whose {@code run} method is invoked when this thread
* is started. If {@code null}, this thread's run method is invoked.
*
* @param name
* the name of the new thread
*/
public
Thread(
Runnable target,
String name) {
init(null,
target,
name, 0);
}
/**
* Allocates a new {@code Thread} object so that it has {@code target}
* as its run object, has the specified {@code name} as its name,
* and belongs to the thread group referred to by {@code group}.
*
* <p>If there is a security manager, its
* {@link SecurityManager#checkAccess(ThreadGroup) checkAccess}
* method is invoked with the ThreadGroup as its argument.
*
* <p>In addition, its {@code checkPermission} method is invoked with
* the {@code RuntimePermission("enableContextClassLoaderOverride")}
* permission when invoked directly or indirectly by the constructor
* of a subclass which overrides the {@code getContextClassLoader}
* or {@code setContextClassLoader} methods.
*
* <p>The priority of the newly created thread is set equal to the
* priority of the thread creating it, that is, the currently running
* thread. The method {@linkplain #setPriority setPriority} may be
* used to change the priority to a new value.
*
* <p>The newly created thread is initially marked as being a daemon
* thread if and only if the thread creating it is currently marked
* as a daemon thread. The method {@linkplain #setDaemon setDaemon}
* may be used to change whether or not a thread is a daemon.
*
* @param group
* the thread group. If {@code null} and there is a security
* manager, the group is determined by {@linkplain
* SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
* If there is not a security manager or {@code
* SecurityManager.getThreadGroup()} returns {@code null}, the group
* is set to the current thread's thread group.
*
* @param target
* the object whose {@code run} method is invoked when this thread
* is started. If {@code null}, this thread's run method is invoked.
*
* @param name
* the name of the new thread
*
* @throws SecurityException
* if the current thread cannot create a thread in the specified
* thread group or cannot override the context class loader methods.
*/
public
Thread(
ThreadGroup group,
Runnable target,
String name) {
init(
group,
target,
name, 0);
}
/**
* Allocates a new {@code Thread} object so that it has {@code target}
* as its run object, has the specified {@code name} as its name,
* and belongs to the thread group referred to by {@code group}, and has
* the specified <i>stack size</i>.
*
* <p>This constructor is identical to {@link
* #Thread(ThreadGroup,Runnable,String)} with the exception of the fact
* that it allows the thread stack size to be specified. The stack size
* is the approximate number of bytes of address space that the virtual
* machine is to allocate for this thread's stack. <b>The effect of the
* {@code stackSize} parameter, if any, is highly platform dependent.</b>
*
* <p>On some platforms, specifying a higher value for the
* {@code stackSize} parameter may allow a thread to achieve greater
* recursion depth before throwing a {@link StackOverflowError}.
* Similarly, specifying a lower value may allow a greater number of
* threads to exist concurrently without throwing an {@link
* OutOfMemoryError} (or other internal error). The details of
* the relationship between the value of the <tt>stackSize</tt> parameter
* and the maximum recursion depth and concurrency level are
* platform-dependent. <b>On some platforms, the value of the
* {@code stackSize} parameter may have no effect whatsoever.</b>
*
* <p>The virtual machine is free to treat the {@code stackSize}
* parameter as a suggestion. If the specified value is unreasonably low
* for the platform, the virtual machine may instead use some
* platform-specific minimum value; if the specified value is unreasonably
* high, the virtual machine may instead use some platform-specific
* maximum. Likewise, the virtual machine is free to round the specified
* value up or down as it sees fit (or to ignore it completely).
*
* <p>Specifying a value of zero for the {@code stackSize} parameter will
* cause this constructor to behave exactly like the
* {@code Thread(ThreadGroup, Runnable, String)} constructor.
*
* <p><i>Due to the platform-dependent nature of the behavior of this
* constructor, extreme care should be exercised in its use.
* The thread stack size necessary to perform a given computation will
* likely vary from one JRE implementation to another. In light of this
* variation, careful tuning of the stack size parameter may be required,
* and the tuning may need to be repeated for each JRE implementation on
* which an application is to run.</i>
*
* <p>Implementation note: Java platform implementers are encouraged to
* document their implementation's behavior with respect to the
* {@code stackSize} parameter.
*
*
* @param group
* the thread group. If {@code null} and there is a security
* manager, the group is determined by {@linkplain
* SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
* If there is not a security manager or {@code
* SecurityManager.getThreadGroup()} returns {@code null}, the group
* is set to the current thread's thread group.
*
* @param target
* the object whose {@code run} method is invoked when this thread
* is started. If {@code null}, this thread's run method is invoked.
*
* @param name
* the name of the new thread
*
* @param stackSize
* the desired stack size for the new thread, or zero to indicate
* that this parameter is to be ignored.
*
* @throws SecurityException
* if the current thread cannot create a thread in the specified
* thread group
*
* @since 1.4
*/
public
Thread(
ThreadGroup group,
Runnable target,
String name,
long
stackSize) {
init(
group,
target,
name,
stackSize);
}
/**
* Causes this thread to begin execution; the Java Virtual Machine
* calls the <code>run</code> method of this thread.
* <p>
* The result is that two threads are running concurrently: the
* current thread (which returns from the call to the
* <code>start</code> method) and the other thread (which executes its
* <code>run</code> method).
* <p>
* It is never legal to start a thread more than once.
* In particular, a thread may not be restarted once it has completed
* execution.
*
* @exception IllegalThreadStateException if the thread was already
* started.
* @see #run()
* @see #stop()
*/
public synchronized void
start() {
/**
* This method is not invoked for the main method thread or "system"
* group threads created/set up by the VM. Any new functionality added
* to this method in the future may have to also be added to the VM.
*
* A zero status value corresponds to state "NEW".
*/
if (
threadStatus != 0)
throw new
IllegalThreadStateException();
/* Notify the group that this thread is about to be started
* so that it can be added to the group's list of threads
* and the group's unstarted count can be decremented. */
group.
add(this);
boolean
started = false;
try {
start0();
started = true;
} finally {
try {
if (!
started) {
group.
threadStartFailed(this);
}
} catch (
Throwable ignore) {
/* do nothing. If start0 threw a Throwable then
it will be passed up the call stack */
}
}
}
private native void
start0();
/**
* If this thread was constructed using a separate
* <code>Runnable</code> run object, then that
* <code>Runnable</code> object's <code>run</code> method is called;
* otherwise, this method does nothing and returns.
* <p>
* Subclasses of <code>Thread</code> should override this method.
*
* @see #start()
* @see #stop()
* @see #Thread(ThreadGroup, Runnable, String)
*/
@
Override
public void
run() {
if (
target != null) {
target.
run();
}
}
/**
* This method is called by the system to give a Thread
* a chance to clean up before it actually exits.
*/
private void
exit() {
if (
group != null) {
group.
threadTerminated(this);
group = null;
}
/* Aggressively null out all reference fields: see bug 4006245 */
target = null;
/* Speed the release of some of these resources */
threadLocals = null;
inheritableThreadLocals = null;
inheritedAccessControlContext = null;
blocker = null;
uncaughtExceptionHandler = null;
}
/**
* Forces the thread to stop executing.
* <p>
* If there is a security manager installed, its <code>checkAccess</code>
* method is called with <code>this</code>
* as its argument. This may result in a
* <code>SecurityException</code> being raised (in the current thread).
* <p>
* If this thread is different from the current thread (that is, the current
* thread is trying to stop a thread other than itself), the
* security manager's <code>checkPermission</code> method (with a
* <code>RuntimePermission("stopThread")</code> argument) is called in
* addition.
* Again, this may result in throwing a
* <code>SecurityException</code> (in the current thread).
* <p>
* The thread represented by this thread is forced to stop whatever
* it is doing abnormally and to throw a newly created
* <code>ThreadDeath</code> object as an exception.
* <p>
* It is permitted to stop a thread that has not yet been started.
* If the thread is eventually started, it immediately terminates.
* <p>
* An application should not normally try to catch
* <code>ThreadDeath</code> unless it must do some extraordinary
* cleanup operation (note that the throwing of
* <code>ThreadDeath</code> causes <code>finally</code> clauses of
* <code>try</code> statements to be executed before the thread
* officially dies). If a <code>catch</code> clause catches a
* <code>ThreadDeath</code> object, it is important to rethrow the
* object so that the thread actually dies.
* <p>
* The top-level error handler that reacts to otherwise uncaught
* exceptions does not print out a message or otherwise notify the
* application if the uncaught exception is an instance of
* <code>ThreadDeath</code>.
*
* @exception SecurityException if the current thread cannot
* modify this thread.
* @see #interrupt()
* @see #checkAccess()
* @see #run()
* @see #start()
* @see ThreadDeath
* @see ThreadGroup#uncaughtException(Thread,Throwable)
* @see SecurityManager#checkAccess(Thread)
* @see SecurityManager#checkPermission
* @deprecated This method is inherently unsafe. Stopping a thread with
* Thread.stop causes it to unlock all of the monitors that it
* has locked (as a natural consequence of the unchecked
* <code>ThreadDeath</code> exception propagating up the stack). If
* any of the objects previously protected by these monitors were in
* an inconsistent state, the damaged objects become visible to
* other threads, potentially resulting in arbitrary behavior. Many
* uses of <code>stop</code> should be replaced by code that simply
* modifies some variable to indicate that the target thread should
* stop running. The target thread should check this variable
* regularly, and return from its run method in an orderly fashion
* if the variable indicates that it is to stop running. If the
* target thread waits for long periods (on a condition variable,
* for example), the <code>interrupt</code> method should be used to
* interrupt the wait.
* For more information, see
* <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">Why
* are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
*/
@
Deprecated
public final void
stop() {
SecurityManager security =
System.
getSecurityManager();
if (
security != null) {
checkAccess();
if (this !=
Thread.
currentThread()) {
security.
checkPermission(
SecurityConstants.
STOP_THREAD_PERMISSION);
}
}
// A zero status value corresponds to "NEW", it can't change to
// not-NEW because we hold the lock.
if (
threadStatus != 0) {
resume(); // Wake up thread if it was suspended; no-op otherwise
}
// The VM can handle all thread states
stop0(new
ThreadDeath());
}
/**
* Throws {@code UnsupportedOperationException}.
*
* @param obj ignored
*
* @deprecated This method was originally designed to force a thread to stop
* and throw a given {@code Throwable} as an exception. It was
* inherently unsafe (see {@link #stop()} for details), and furthermore
* could be used to generate exceptions that the target thread was
* not prepared to handle.
* For more information, see
* <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">Why
* are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
*/
@
Deprecated
public final synchronized void
stop(
Throwable obj) {
throw new
UnsupportedOperationException();
}
/**
* Interrupts this thread.
*
* <p> Unless the current thread is interrupting itself, which is
* always permitted, the {@link #checkAccess() checkAccess} method
* of this thread is invoked, which may cause a {@link
* SecurityException} to be thrown.
*
* <p> If this thread is blocked in an invocation of the {@link
* Object#wait() wait()}, {@link Object#wait(long) wait(long)}, or {@link
* Object#wait(long, int) wait(long, int)} methods of the {@link Object}
* class, or of the {@link #join()}, {@link #join(long)}, {@link
* #join(long, int)}, {@link #sleep(long)}, or {@link #sleep(long, int)},
* methods of this class, then its interrupt status will be cleared and it
* will receive an {@link InterruptedException}.
*
* <p> If this thread is blocked in an I/O operation upon an {@link
* java.nio.channels.InterruptibleChannel InterruptibleChannel}
* then the channel will be closed, the thread's interrupt
* status will be set, and the thread will receive a {@link
* java.nio.channels.ClosedByInterruptException}.
*
* <p> If this thread is blocked in a {@link java.nio.channels.Selector}
* then the thread's interrupt status will be set and it will return
* immediately from the selection operation, possibly with a non-zero
* value, just as if the selector's {@link
* java.nio.channels.Selector#wakeup wakeup} method were invoked.
*
* <p> If none of the previous conditions hold then this thread's interrupt
* status will be set. </p>
*
* <p> Interrupting a thread that is not alive need not have any effect.
*
* @throws SecurityException
* if the current thread cannot modify this thread
*
* @revised 6.0
* @spec JSR-51
*/
public void
interrupt() {
if (this !=
Thread.
currentThread())
checkAccess();
synchronized (
blockerLock) {
Interruptible b =
blocker;
if (
b != null) {
interrupt0(); // Just to set the interrupt flag
b.
interrupt(this);
return;
}
}
interrupt0();
}
/**
* Tests whether the current thread has been interrupted. The
* <i>interrupted status</i> of the thread is cleared by this method. In
* other words, if this method were to be called twice in succession, the
* second call would return false (unless the current thread were
* interrupted again, after the first call had cleared its interrupted
* status and before the second call had examined it).
*
* <p>A thread interruption ignored because a thread was not alive
* at the time of the interrupt will be reflected by this method
* returning false.
*
* @return <code>true</code> if the current thread has been interrupted;
* <code>false</code> otherwise.
* @see #isInterrupted()
* @revised 6.0
*/
public static boolean
interrupted() {
return
currentThread().
isInterrupted(true);
}
/**
* Tests whether this thread has been interrupted. The <i>interrupted
* status</i> of the thread is unaffected by this method.
*
* <p>A thread interruption ignored because a thread was not alive
* at the time of the interrupt will be reflected by this method
* returning false.
*
* @return <code>true</code> if this thread has been interrupted;
* <code>false</code> otherwise.
* @see #interrupted()
* @revised 6.0
*/
public boolean
isInterrupted() {
return
isInterrupted(false);
}
/**
* Tests if some Thread has been interrupted. The interrupted state
* is reset or not based on the value of ClearInterrupted that is
* passed.
*/
private native boolean
isInterrupted(boolean
ClearInterrupted);
/**
* Throws {@link NoSuchMethodError}.
*
* @deprecated This method was originally designed to destroy this
* thread without any cleanup. Any monitors it held would have
* remained locked. However, the method was never implemented.
* If if were to be implemented, it would be deadlock-prone in
* much the manner of {@link #suspend}. If the target thread held
* a lock protecting a critical system resource when it was
* destroyed, no thread could ever access this resource again.
* If another thread ever attempted to lock this resource, deadlock
* would result. Such deadlocks typically manifest themselves as
* "frozen" processes. For more information, see
* <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">
* Why are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
* @throws NoSuchMethodError always
*/
@
Deprecated
public void
destroy() {
throw new
NoSuchMethodError();
}
/**
* Tests if this thread is alive. A thread is alive if it has
* been started and has not yet died.
*
* @return <code>true</code> if this thread is alive;
* <code>false</code> otherwise.
*/
public final native boolean
isAlive();
/**
* Suspends this thread.
* <p>
* First, the <code>checkAccess</code> method of this thread is called
* with no arguments. This may result in throwing a
* <code>SecurityException </code>(in the current thread).
* <p>
* If the thread is alive, it is suspended and makes no further
* progress unless and until it is resumed.
*
* @exception SecurityException if the current thread cannot modify
* this thread.
* @see #checkAccess
* @deprecated This method has been deprecated, as it is
* inherently deadlock-prone. If the target thread holds a lock on the
* monitor protecting a critical system resource when it is suspended, no
* thread can access this resource until the target thread is resumed. If
* the thread that would resume the target thread attempts to lock this
* monitor prior to calling <code>resume</code>, deadlock results. Such
* deadlocks typically manifest themselves as "frozen" processes.
* For more information, see
* <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">Why
* are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
*/
@
Deprecated
public final void
suspend() {
checkAccess();
suspend0();
}
/**
* Resumes a suspended thread.
* <p>
* First, the <code>checkAccess</code> method of this thread is called
* with no arguments. This may result in throwing a
* <code>SecurityException</code> (in the current thread).
* <p>
* If the thread is alive but suspended, it is resumed and is
* permitted to make progress in its execution.
*
* @exception SecurityException if the current thread cannot modify this
* thread.
* @see #checkAccess
* @see #suspend()
* @deprecated This method exists solely for use with {@link #suspend},
* which has been deprecated because it is deadlock-prone.
* For more information, see
* <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">Why
* are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
*/
@
Deprecated
public final void
resume() {
checkAccess();
resume0();
}
/**
* Changes the priority of this thread.
* <p>
* First the <code>checkAccess</code> method of this thread is called
* with no arguments. This may result in throwing a
* <code>SecurityException</code>.
* <p>
* Otherwise, the priority of this thread is set to the smaller of
* the specified <code>newPriority</code> and the maximum permitted
* priority of the thread's thread group.
*
* @param newPriority priority to set this thread to
* @exception IllegalArgumentException If the priority is not in the
* range <code>MIN_PRIORITY</code> to
* <code>MAX_PRIORITY</code>.
* @exception SecurityException if the current thread cannot modify
* this thread.
* @see #getPriority
* @see #checkAccess()
* @see #getThreadGroup()
* @see #MAX_PRIORITY
* @see #MIN_PRIORITY
* @see ThreadGroup#getMaxPriority()
*/
public final void
setPriority(int
newPriority) {
ThreadGroup g;
checkAccess();
if (
newPriority >
MAX_PRIORITY ||
newPriority <
MIN_PRIORITY) {
throw new
IllegalArgumentException();
}
if((
g =
getThreadGroup()) != null) {
if (
newPriority >
g.
getMaxPriority()) {
newPriority =
g.
getMaxPriority();
}
setPriority0(
priority =
newPriority);
}
}
/**
* Returns this thread's priority.
*
* @return this thread's priority.
* @see #setPriority
*/
public final int
getPriority() {
return
priority;
}
/**
* Changes the name of this thread to be equal to the argument
* <code>name</code>.
* <p>
* First the <code>checkAccess</code> method of this thread is called
* with no arguments. This may result in throwing a
* <code>SecurityException</code>.
*
* @param name the new name for this thread.
* @exception SecurityException if the current thread cannot modify this
* thread.
* @see #getName
* @see #checkAccess()
*/
public final synchronized void
setName(
String name) {
checkAccess();
if (
name == null) {
throw new
NullPointerException("name cannot be null");
}
this.
name =
name;
if (
threadStatus != 0) {
setNativeName(
name);
}
}
/**
* Returns this thread's name.
*
* @return this thread's name.
* @see #setName(String)
*/
public final
String getName() {
return
name;
}
/**
* Returns the thread group to which this thread belongs.
* This method returns null if this thread has died
* (been stopped).
*
* @return this thread's thread group.
*/
public final
ThreadGroup getThreadGroup() {
return
group;
}
/**
* Returns an estimate of the number of active threads in the current
* thread's {@linkplain java.lang.ThreadGroup thread group} and its
* subgroups. Recursively iterates over all subgroups in the current
* thread's thread group.
*
* <p> The value returned is only an estimate because the number of
* threads may change dynamically while this method traverses internal
* data structures, and might be affected by the presence of certain
* system threads. This method is intended primarily for debugging
* and monitoring purposes.
*
* @return an estimate of the number of active threads in the current
* thread's thread group and in any other thread group that
* has the current thread's thread group as an ancestor
*/
public static int
activeCount() {
return
currentThread().
getThreadGroup().
activeCount();
}
/**
* Copies into the specified array every active thread in the current
* thread's thread group and its subgroups. This method simply
* invokes the {@link java.lang.ThreadGroup#enumerate(Thread[])}
* method of the current thread's thread group.
*
* <p> An application might use the {@linkplain #activeCount activeCount}
* method to get an estimate of how big the array should be, however
* <i>if the array is too short to hold all the threads, the extra threads
* are silently ignored.</i> If it is critical to obtain every active
* thread in the current thread's thread group and its subgroups, the
* invoker should verify that the returned int value is strictly less
* than the length of {@code tarray}.
*
* <p> Due to the inherent race condition in this method, it is recommended
* that the method only be used for debugging and monitoring purposes.
*
* @param tarray
* an array into which to put the list of threads
*
* @return the number of threads put into the array
*
* @throws SecurityException
* if {@link java.lang.ThreadGroup#checkAccess} determines that
* the current thread cannot access its thread group
*/
public static int
enumerate(
Thread tarray[]) {
return
currentThread().
getThreadGroup().
enumerate(
tarray);
}
/**
* Counts the number of stack frames in this thread. The thread must
* be suspended.
*
* @return the number of stack frames in this thread.
* @exception IllegalThreadStateException if this thread is not
* suspended.
* @deprecated The definition of this call depends on {@link #suspend},
* which is deprecated. Further, the results of this call
* were never well-defined.
*/
@
Deprecated
public native int
countStackFrames();
/**
* Waits at most {@code millis} milliseconds for this thread to
* die. A timeout of {@code 0} means to wait forever.
*
* <p> This implementation uses a loop of {@code this.wait} calls
* conditioned on {@code this.isAlive}. As a thread terminates the
* {@code this.notifyAll} method is invoked. It is recommended that
* applications not use {@code wait}, {@code notify}, or
* {@code notifyAll} on {@code Thread} instances.
*
* @param millis
* the time to wait in milliseconds
*
* @throws IllegalArgumentException
* if the value of {@code millis} is negative
*
* @throws InterruptedException
* if any thread has interrupted the current thread. The
* <i>interrupted status</i> of the current thread is
* cleared when this exception is thrown.
*/
public final synchronized void
join(long
millis)
throws
InterruptedException {
long
base =
System.
currentTimeMillis();
long
now = 0;
if (
millis < 0) {
throw new
IllegalArgumentException("timeout value is negative");
}
if (
millis == 0) {
while (
isAlive()) {
wait(0);
}
} else {
while (
isAlive()) {
long
delay =
millis -
now;
if (
delay <= 0) {
break;
}
wait(
delay);
now =
System.
currentTimeMillis() -
base;
}
}
}
/**
* Waits at most {@code millis} milliseconds plus
* {@code nanos} nanoseconds for this thread to die.
*
* <p> This implementation uses a loop of {@code this.wait} calls
* conditioned on {@code this.isAlive}. As a thread terminates the
* {@code this.notifyAll} method is invoked. It is recommended that
* applications not use {@code wait}, {@code notify}, or
* {@code notifyAll} on {@code Thread} instances.
*
* @param millis
* the time to wait in milliseconds
*
* @param nanos
* {@code 0-999999} additional nanoseconds to wait
*
* @throws IllegalArgumentException
* if the value of {@code millis} is negative, or the value
* of {@code nanos} is not in the range {@code 0-999999}
*
* @throws InterruptedException
* if any thread has interrupted the current thread. The
* <i>interrupted status</i> of the current thread is
* cleared when this exception is thrown.
*/
public final synchronized void
join(long
millis, int
nanos)
throws
InterruptedException {
if (
millis < 0) {
throw new
IllegalArgumentException("timeout value is negative");
}
if (
nanos < 0 ||
nanos > 999999) {
throw new
IllegalArgumentException(
"nanosecond timeout value out of range");
}
if (
nanos >= 500000 || (
nanos != 0 &&
millis == 0)) {
millis++;
}
join(
millis);
}
/**
* Waits for this thread to die.
*
* <p> An invocation of this method behaves in exactly the same
* way as the invocation
*
* <blockquote>
* {@linkplain #join(long) join}{@code (0)}
* </blockquote>
*
* @throws InterruptedException
* if any thread has interrupted the current thread. The
* <i>interrupted status</i> of the current thread is
* cleared when this exception is thrown.
*/
public final void
join() throws
InterruptedException {
join(0);
}
/**
* Prints a stack trace of the current thread to the standard error stream.
* This method is used only for debugging.
*
* @see Throwable#printStackTrace()
*/
public static void
dumpStack() {
new
Exception("Stack trace").
printStackTrace();
}
/**
* Marks this thread as either a {@linkplain #isDaemon daemon} thread
* or a user thread. The Java Virtual Machine exits when the only
* threads running are all daemon threads.
*
* <p> This method must be invoked before the thread is started.
*
* @param on
* if {@code true}, marks this thread as a daemon thread
*
* @throws IllegalThreadStateException
* if this thread is {@linkplain #isAlive alive}
*
* @throws SecurityException
* if {@link #checkAccess} determines that the current
* thread cannot modify this thread
*/
public final void
setDaemon(boolean
on) {
checkAccess();
if (
isAlive()) {
throw new
IllegalThreadStateException();
}
daemon =
on;
}
/**
* Tests if this thread is a daemon thread.
*
* @return <code>true</code> if this thread is a daemon thread;
* <code>false</code> otherwise.
* @see #setDaemon(boolean)
*/
public final boolean
isDaemon() {
return
daemon;
}
/**
* Determines if the currently running thread has permission to
* modify this thread.
* <p>
* If there is a security manager, its <code>checkAccess</code> method
* is called with this thread as its argument. This may result in
* throwing a <code>SecurityException</code>.
*
* @exception SecurityException if the current thread is not allowed to
* access this thread.
* @see SecurityManager#checkAccess(Thread)
*/
public final void
checkAccess() {
SecurityManager security =
System.
getSecurityManager();
if (
security != null) {
security.
checkAccess(this);
}
}
/**
* Returns a string representation of this thread, including the
* thread's name, priority, and thread group.
*
* @return a string representation of this thread.
*/
public
String toString() {
ThreadGroup group =
getThreadGroup();
if (
group != null) {
return "Thread[" +
getName() + "," +
getPriority() + "," +
group.
getName() + "]";
} else {
return "Thread[" +
getName() + "," +
getPriority() + "," +
"" + "]";
}
}
/**
* Returns the context ClassLoader for this Thread. The context
* ClassLoader is provided by the creator of the thread for use
* by code running in this thread when loading classes and resources.
* If not {@linkplain #setContextClassLoader set}, the default is the
* ClassLoader context of the parent Thread. The context ClassLoader of the
* primordial thread is typically set to the class loader used to load the
* application.
*
* <p>If a security manager is present, and the invoker's class loader is not
* {@code null} and is not the same as or an ancestor of the context class
* loader, then this method invokes the security manager's {@link
* SecurityManager#checkPermission(java.security.Permission) checkPermission}
* method with a {@link RuntimePermission RuntimePermission}{@code
* ("getClassLoader")} permission to verify that retrieval of the context
* class loader is permitted.
*
* @return the context ClassLoader for this Thread, or {@code null}
* indicating the system class loader (or, failing that, the
* bootstrap class loader)
*
* @throws SecurityException
* if the current thread cannot get the context ClassLoader
*
* @since 1.2
*/
@
CallerSensitive
public
ClassLoader getContextClassLoader() {
if (
contextClassLoader == null)
return null;
SecurityManager sm =
System.
getSecurityManager();
if (
sm != null) {
ClassLoader.
checkClassLoaderPermission(
contextClassLoader,
Reflection.
getCallerClass());
}
return
contextClassLoader;
}
/**
* Sets the context ClassLoader for this Thread. The context
* ClassLoader can be set when a thread is created, and allows
* the creator of the thread to provide the appropriate class loader,
* through {@code getContextClassLoader}, to code running in the thread
* when loading classes and resources.
*
* <p>If a security manager is present, its {@link
* SecurityManager#checkPermission(java.security.Permission) checkPermission}
* method is invoked with a {@link RuntimePermission RuntimePermission}{@code
* ("setContextClassLoader")} permission to see if setting the context
* ClassLoader is permitted.
*
* @param cl
* the context ClassLoader for this Thread, or null indicating the
* system class loader (or, failing that, the bootstrap class loader)
*
* @throws SecurityException
* if the current thread cannot set the context ClassLoader
*
* @since 1.2
*/
public void
setContextClassLoader(
ClassLoader cl) {
SecurityManager sm =
System.
getSecurityManager();
if (
sm != null) {
sm.
checkPermission(new
RuntimePermission("setContextClassLoader"));
}
contextClassLoader =
cl;
}
/**
* Returns <tt>true</tt> if and only if the current thread holds the
* monitor lock on the specified object.
*
* <p>This method is designed to allow a program to assert that
* the current thread already holds a specified lock:
* <pre>
* assert Thread.holdsLock(obj);
* </pre>
*
* @param obj the object on which to test lock ownership
* @throws NullPointerException if obj is <tt>null</tt>
* @return <tt>true</tt> if the current thread holds the monitor lock on
* the specified object.
* @since 1.4
*/
public static native boolean
holdsLock(
Object obj);
private static final
StackTraceElement[]
EMPTY_STACK_TRACE
= new
StackTraceElement[0];
/**
* Returns an array of stack trace elements representing the stack dump
* of this thread. This method will return a zero-length array if
* this thread has not started, has started but has not yet been
* scheduled to run by the system, or has terminated.
* If the returned array is of non-zero length then the first element of
* the array represents the top of the stack, which is the most recent
* method invocation in the sequence. The last element of the array
* represents the bottom of the stack, which is the least recent method
* invocation in the sequence.
*
* <p>If there is a security manager, and this thread is not
* the current thread, then the security manager's
* <tt>checkPermission</tt> method is called with a
* <tt>RuntimePermission("getStackTrace")</tt> permission
* to see if it's ok to get the stack trace.
*
* <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 thread is permitted to return a zero-length array from this
* method.
*
* @return an array of <tt>StackTraceElement</tt>,
* each represents one stack frame.
*
* @throws SecurityException
* if a security manager exists and its
* <tt>checkPermission</tt> method doesn't allow
* getting the stack trace of thread.
* @see SecurityManager#checkPermission
* @see RuntimePermission
* @see Throwable#getStackTrace
*
* @since 1.5
*/
public
StackTraceElement[]
getStackTrace() {
if (this !=
Thread.
currentThread()) {
// check for getStackTrace permission
SecurityManager security =
System.
getSecurityManager();
if (
security != null) {
security.
checkPermission(
SecurityConstants.
GET_STACK_TRACE_PERMISSION);
}
// optimization so we do not call into the vm for threads that
// have not yet started or have terminated
if (!
isAlive()) {
return
EMPTY_STACK_TRACE;
}
StackTraceElement[][]
stackTraceArray =
dumpThreads(new
Thread[] {this});
StackTraceElement[]
stackTrace =
stackTraceArray[0];
// a thread that was alive during the previous isAlive call may have
// since terminated, therefore not having a stacktrace.
if (
stackTrace == null) {
stackTrace =
EMPTY_STACK_TRACE;
}
return
stackTrace;
} else {
// Don't need JVM help for current thread
return (new
Exception()).
getStackTrace();
}
}
/**
* Returns a map of stack traces for all live threads.
* The map keys are threads and each map value is an array of
* <tt>StackTraceElement</tt> that represents the stack dump
* of the corresponding <tt>Thread</tt>.
* The returned stack traces are in the format specified for
* the {@link #getStackTrace getStackTrace} method.
*
* <p>The threads may be executing while this method is called.
* The stack trace of each thread only represents a snapshot and
* each stack trace may be obtained at different time. A zero-length
* array will be returned in the map value if the virtual machine has
* no stack trace information about a thread.
*
* <p>If there is a security manager, then the security manager's
* <tt>checkPermission</tt> method is called with a
* <tt>RuntimePermission("getStackTrace")</tt> permission as well as
* <tt>RuntimePermission("modifyThreadGroup")</tt> permission
* to see if it is ok to get the stack trace of all threads.
*
* @return a <tt>Map</tt> from <tt>Thread</tt> to an array of
* <tt>StackTraceElement</tt> that represents the stack trace of
* the corresponding thread.
*
* @throws SecurityException
* if a security manager exists and its
* <tt>checkPermission</tt> method doesn't allow
* getting the stack trace of thread.
* @see #getStackTrace
* @see SecurityManager#checkPermission
* @see RuntimePermission
* @see Throwable#getStackTrace
*
* @since 1.5
*/
public static
Map<
Thread,
StackTraceElement[]>
getAllStackTraces() {
// check for getStackTrace permission
SecurityManager security =
System.
getSecurityManager();
if (
security != null) {
security.
checkPermission(
SecurityConstants.
GET_STACK_TRACE_PERMISSION);
security.
checkPermission(
SecurityConstants.
MODIFY_THREADGROUP_PERMISSION);
}
// Get a snapshot of the list of all threads
Thread[]
threads =
getThreads();
StackTraceElement[][]
traces =
dumpThreads(
threads);
Map<
Thread,
StackTraceElement[]>
m = new
HashMap<>(
threads.length);
for (int
i = 0;
i <
threads.length;
i++) {
StackTraceElement[]
stackTrace =
traces[
i];
if (
stackTrace != null) {
m.
put(
threads[
i],
stackTrace);
}
// else terminated so we don't put it in the map
}
return
m;
}
private static final
RuntimePermission SUBCLASS_IMPLEMENTATION_PERMISSION =
new
RuntimePermission("enableContextClassLoaderOverride");
/** cache of subclass security audit results */
/* Replace with ConcurrentReferenceHashMap when/if it appears in a future
* release */
private static class
Caches {
/** cache of subclass security audit results */
static final
ConcurrentMap<
WeakClassKey,
Boolean>
subclassAudits =
new
ConcurrentHashMap<>();
/** queue for WeakReferences to audited subclasses */
static final
ReferenceQueue<
Class<?>>
subclassAuditsQueue =
new
ReferenceQueue<>();
}
/**
* Verifies that this (possibly subclass) instance can be constructed
* without violating security constraints: the subclass must not override
* security-sensitive non-final methods, or else the
* "enableContextClassLoaderOverride" RuntimePermission is checked.
*/
private static boolean
isCCLOverridden(
Class<?>
cl) {
if (
cl ==
Thread.class)
return false;
processQueue(
Caches.
subclassAuditsQueue,
Caches.
subclassAudits);
WeakClassKey key = new
WeakClassKey(
cl,
Caches.
subclassAuditsQueue);
Boolean result =
Caches.
subclassAudits.
get(
key);
if (
result == null) {
result =
Boolean.
valueOf(
auditSubclass(
cl));
Caches.
subclassAudits.
putIfAbsent(
key,
result);
}
return
result.
booleanValue();
}
/**
* Performs reflective checks on given subclass to verify that it doesn't
* override security-sensitive non-final methods. Returns true if the
* subclass overrides any of the methods, false otherwise.
*/
private static boolean
auditSubclass(final
Class<?>
subcl) {
Boolean result =
AccessController.
doPrivileged(
new
PrivilegedAction<
Boolean>() {
public
Boolean run() {
for (
Class<?>
cl =
subcl;
cl !=
Thread.class;
cl =
cl.
getSuperclass())
{
try {
cl.
getDeclaredMethod("getContextClassLoader", new
Class<?>[0]);
return
Boolean.
TRUE;
} catch (
NoSuchMethodException ex) {
}
try {
Class<?>[]
params = {
ClassLoader.class};
cl.
getDeclaredMethod("setContextClassLoader",
params);
return
Boolean.
TRUE;
} catch (
NoSuchMethodException ex) {
}
}
return
Boolean.
FALSE;
}
}
);
return
result.
booleanValue();
}
private native static
StackTraceElement[][]
dumpThreads(
Thread[]
threads);
private native static
Thread[]
getThreads();
/**
* Returns the identifier of this Thread. The thread ID is a positive
* <tt>long</tt> number generated when this thread was created.
* The thread ID is unique and remains unchanged during its lifetime.
* When a thread is terminated, this thread ID may be reused.
*
* @return this thread's ID.
* @since 1.5
*/
public long
getId() {
return
tid;
}
/**
* A thread state. A thread can be in one of the following states:
* <ul>
* <li>{@link #NEW}<br>
* A thread that has not yet started is in this state.
* </li>
* <li>{@link #RUNNABLE}<br>
* A thread executing in the Java virtual machine is in this state.
* </li>
* <li>{@link #BLOCKED}<br>
* A thread that is blocked waiting for a monitor lock
* is in this state.
* </li>
* <li>{@link #WAITING}<br>
* A thread that is waiting indefinitely for another thread to
* perform a particular action is in this state.
* </li>
* <li>{@link #TIMED_WAITING}<br>
* A thread that is waiting for another thread to perform an action
* for up to a specified waiting time is in this state.
* </li>
* <li>{@link #TERMINATED}<br>
* A thread that has exited is in this state.
* </li>
* </ul>
*
* <p>
* A thread can be in only one state at a given point in time.
* These states are virtual machine states which do not reflect
* any operating system thread states.
*
* @since 1.5
* @see #getState
*/
public enum
State {
/**
* Thread state for a thread which has not yet started.
*/
NEW,
/**
* Thread state for a runnable thread. A thread in the runnable
* state is executing in the Java virtual machine but it may
* be waiting for other resources from the operating system
* such as processor.
*/
RUNNABLE,
/**
* Thread state for a thread blocked waiting for a monitor lock.
* A thread in the blocked state is waiting for a monitor lock
* to enter a synchronized block/method or
* reenter a synchronized block/method after calling
* {@link Object#wait() Object.wait}.
*/
BLOCKED,
/**
* Thread state for a waiting thread.
* A thread is in the waiting state due to calling one of the
* following methods:
* <ul>
* <li>{@link Object#wait() Object.wait} with no timeout</li>
* <li>{@link #join() Thread.join} with no timeout</li>
* <li>{@link LockSupport#park() LockSupport.park}</li>
* </ul>
*
* <p>A thread in the waiting state is waiting for another thread to
* perform a particular action.
*
* For example, a thread that has called <tt>Object.wait()</tt>
* on an object is waiting for another thread to call
* <tt>Object.notify()</tt> or <tt>Object.notifyAll()</tt> on
* that object. A thread that has called <tt>Thread.join()</tt>
* is waiting for a specified thread to terminate.
*/
WAITING,
/**
* Thread state for a waiting thread with a specified waiting time.
* A thread is in the timed waiting state due to calling one of
* the following methods with a specified positive waiting time:
* <ul>
* <li>{@link #sleep Thread.sleep}</li>
* <li>{@link Object#wait(long) Object.wait} with timeout</li>
* <li>{@link #join(long) Thread.join} with timeout</li>
* <li>{@link LockSupport#parkNanos LockSupport.parkNanos}</li>
* <li>{@link LockSupport#parkUntil LockSupport.parkUntil}</li>
* </ul>
*/
TIMED_WAITING,
/**
* Thread state for a terminated thread.
* The thread has completed execution.
*/
TERMINATED;
}
/**
* Returns the state of this thread.
* This method is designed for use in monitoring of the system state,
* not for synchronization control.
*
* @return this thread's state.
* @since 1.5
*/
public
State getState() {
// get current thread state
return sun.misc.
VM.
toThreadState(
threadStatus);
}
// Added in JSR-166
/**
* Interface for handlers invoked when a <tt>Thread</tt> abruptly
* terminates due to an uncaught exception.
* <p>When a thread is about to terminate due to an uncaught exception
* the Java Virtual Machine will query the thread for its
* <tt>UncaughtExceptionHandler</tt> using
* {@link #getUncaughtExceptionHandler} and will invoke the handler's
* <tt>uncaughtException</tt> method, passing the thread and the
* exception as arguments.
* If a thread has not had its <tt>UncaughtExceptionHandler</tt>
* explicitly set, then its <tt>ThreadGroup</tt> object acts as its
* <tt>UncaughtExceptionHandler</tt>. If the <tt>ThreadGroup</tt> object
* has no
* special requirements for dealing with the exception, it can forward
* the invocation to the {@linkplain #getDefaultUncaughtExceptionHandler
* default uncaught exception handler}.
*
* @see #setDefaultUncaughtExceptionHandler
* @see #setUncaughtExceptionHandler
* @see ThreadGroup#uncaughtException
* @since 1.5
*/
@
FunctionalInterface
public interface
UncaughtExceptionHandler {
/**
* Method invoked when the given thread terminates due to the
* given uncaught exception.
* <p>Any exception thrown by this method will be ignored by the
* Java Virtual Machine.
* @param t the thread
* @param e the exception
*/
void
uncaughtException(
Thread t,
Throwable e);
}
// null unless explicitly set
private volatile
UncaughtExceptionHandler uncaughtExceptionHandler;
// null unless explicitly set
private static volatile
UncaughtExceptionHandler defaultUncaughtExceptionHandler;
/**
* Set the default handler invoked when a thread abruptly terminates
* due to an uncaught exception, and no other handler has been defined
* for that thread.
*
* <p>Uncaught exception handling is controlled first by the thread, then
* by the thread's {@link ThreadGroup} object and finally by the default
* uncaught exception handler. If the thread does not have an explicit
* uncaught exception handler set, and the thread's thread group
* (including parent thread groups) does not specialize its
* <tt>uncaughtException</tt> method, then the default handler's
* <tt>uncaughtException</tt> method will be invoked.
* <p>By setting the default uncaught exception handler, an application
* can change the way in which uncaught exceptions are handled (such as
* logging to a specific device, or file) for those threads that would
* already accept whatever "default" behavior the system
* provided.
*
* <p>Note that the default uncaught exception handler should not usually
* defer to the thread's <tt>ThreadGroup</tt> object, as that could cause
* infinite recursion.
*
* @param eh the object to use as the default uncaught exception handler.
* If <tt>null</tt> then there is no default handler.
*
* @throws SecurityException if a security manager is present and it
* denies <tt>{@link RuntimePermission}
* ("setDefaultUncaughtExceptionHandler")</tt>
*
* @see #setUncaughtExceptionHandler
* @see #getUncaughtExceptionHandler
* @see ThreadGroup#uncaughtException
* @since 1.5
*/
public static void
setDefaultUncaughtExceptionHandler(
UncaughtExceptionHandler eh) {
SecurityManager sm =
System.
getSecurityManager();
if (
sm != null) {
sm.
checkPermission(
new
RuntimePermission("setDefaultUncaughtExceptionHandler")
);
}
defaultUncaughtExceptionHandler =
eh;
}
/**
* Returns the default handler invoked when a thread abruptly terminates
* due to an uncaught exception. If the returned value is <tt>null</tt>,
* there is no default.
* @since 1.5
* @see #setDefaultUncaughtExceptionHandler
* @return the default uncaught exception handler for all threads
*/
public static
UncaughtExceptionHandler getDefaultUncaughtExceptionHandler(){
return
defaultUncaughtExceptionHandler;
}
/**
* Returns the handler invoked when this thread abruptly terminates
* due to an uncaught exception. If this thread has not had an
* uncaught exception handler explicitly set then this thread's
* <tt>ThreadGroup</tt> object is returned, unless this thread
* has terminated, in which case <tt>null</tt> is returned.
* @since 1.5
* @return the uncaught exception handler for this thread
*/
public
UncaughtExceptionHandler getUncaughtExceptionHandler() {
return
uncaughtExceptionHandler != null ?
uncaughtExceptionHandler :
group;
}
/**
* Set the handler invoked when this thread abruptly terminates
* due to an uncaught exception.
* <p>A thread can take full control of how it responds to uncaught
* exceptions by having its uncaught exception handler explicitly set.
* If no such handler is set then the thread's <tt>ThreadGroup</tt>
* object acts as its handler.
* @param eh the object to use as this thread's uncaught exception
* handler. If <tt>null</tt> then this thread has no explicit handler.
* @throws SecurityException if the current thread is not allowed to
* modify this thread.
* @see #setDefaultUncaughtExceptionHandler
* @see ThreadGroup#uncaughtException
* @since 1.5
*/
public void
setUncaughtExceptionHandler(
UncaughtExceptionHandler eh) {
checkAccess();
uncaughtExceptionHandler =
eh;
}
/**
* Dispatch an uncaught exception to the handler. This method is
* intended to be called only by the JVM.
*/
private void
dispatchUncaughtException(
Throwable e) {
getUncaughtExceptionHandler().
uncaughtException(this,
e);
}
/**
* Removes from the specified map any keys that have been enqueued
* on the specified reference queue.
*/
static void
processQueue(
ReferenceQueue<
Class<?>>
queue,
ConcurrentMap<? extends
WeakReference<
Class<?>>, ?>
map)
{
Reference<? extends
Class<?>>
ref;
while((
ref =
queue.
poll()) != null) {
map.
remove(
ref);
}
}
/**
* Weak key for Class objects.
**/
static class
WeakClassKey extends
WeakReference<
Class<?>> {
/**
* saved value of the referent's identity hash code, to maintain
* a consistent hash code after the referent has been cleared
*/
private final int
hash;
/**
* Create a new WeakClassKey to the given object, registered
* with a queue.
*/
WeakClassKey(
Class<?>
cl,
ReferenceQueue<
Class<?>>
refQueue) {
super(
cl,
refQueue);
hash =
System.
identityHashCode(
cl);
}
/**
* Returns the identity hash code of the original referent.
*/
@
Override
public int
hashCode() {
return
hash;
}
/**
* Returns true if the given object is this identical
* WeakClassKey instance, or, if this object's referent has not
* been cleared, if the given object is another WeakClassKey
* instance with the identical non-null referent as this one.
*/
@
Override
public boolean
equals(
Object obj) {
if (
obj == this)
return true;
if (
obj instanceof
WeakClassKey) {
Object referent =
get();
return (
referent != null) &&
(
referent == ((
WeakClassKey)
obj).
get());
} else {
return false;
}
}
}
// The following three initially uninitialized fields are exclusively
// managed by class java.util.concurrent.ThreadLocalRandom. These
// fields are used to build the high-performance PRNGs in the
// concurrent code, and we can not risk accidental false sharing.
// Hence, the fields are isolated with @Contended.
/** The current seed for a ThreadLocalRandom */
@sun.misc.
Contended("tlr")
long
threadLocalRandomSeed;
/** Probe hash value; nonzero if threadLocalRandomSeed initialized */
@sun.misc.
Contended("tlr")
int
threadLocalRandomProbe;
/** Secondary seed isolated from public ThreadLocalRandom sequence */
@sun.misc.
Contended("tlr")
int
threadLocalRandomSecondarySeed;
/* Some private helper methods */
private native void
setPriority0(int
newPriority);
private native void
stop0(
Object o);
private native void
suspend0();
private native void
resume0();
private native void
interrupt0();
private native void
setNativeName(
String name);
}