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/OpenJDK 21

Class ForkJoinWorkerThread

java.lang.Object
java.lang.Thread
java.util.concurrent.ForkJoinWorkerThread
All Implemented Interfaces:
Runnable
public class ForkJoinWorkerThread extends Thread
A thread managed by a ForkJoinPool, which executes ForkJoinTasks. This class is subclassable solely for the sake of adding functionality -- there are no overridable methods dealing with scheduling or execution. However, you can override initialization and termination methods surrounding the main task processing loop. If you do create such a subclass, you will also need to supply a custom ForkJoinPool.ForkJoinWorkerThreadFactory to use it in a ForkJoinPool.
Since:
1.7

Nested Class Summary

Nested classes/interfaces declared in class java.lang.Thread

Thread.Builder, Thread.State, Thread.UncaughtExceptionHandler

Field Summary

Fields declared in class java.lang.Thread

MAX_PRIORITY, MIN_PRIORITY, NORM_PRIORITY

Constructor Summary

ForkJoinWorkerThread(ThreadGroup group, ForkJoinPool pool, boolean preserveThreadLocals)
ForkJoinWorkerThread(ForkJoinPool pool)
Modifier Constructor Description
protected
Creates a ForkJoinWorkerThread operating in the given thread group and pool, and with the given policy for preserving ThreadLocals.
protected
Creates a ForkJoinWorkerThread operating in the given pool.

Method Summary

Modifier and Type Method Description
ForkJoinPool getPool()
Returns the pool hosting this thread.
int getPoolIndex()
Returns the unique index number of this thread in its pool.
int getQueuedTaskCount()
Returns a (non-negative) estimate of the number of tasks in the thread's queue.
protected void onStart()
Initializes internal state after construction but before processing any tasks.
protected void onTermination(Throwable exception)
Performs cleanup associated with termination of this worker thread.
void run()
This method is required to be public, but should never be called explicitly.

Methods declared in class java.lang.Thread

activeCount, checkAccess, clone, countStackFrames, currentThread, dumpStack, enumerate, getAllStackTraces, getContextClassLoader, getDefaultUncaughtExceptionHandler, getId, getName, getPriority, getStackTrace, getState, getThreadGroup, getUncaughtExceptionHandler, holdsLock, interrupt, interrupted, isAlive, isDaemon, isInterrupted, isVirtual, join, join, join, join, ofPlatform, ofVirtual, onSpinWait, resume, setContextClassLoader, setDaemon, setDefaultUncaughtExceptionHandler, setName, setPriority, setUncaughtExceptionHandler, sleep, sleep, sleep, start, startVirtualThread, stop, suspend, threadId, toString, yield

Methods declared in class java.lang.Object

equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Details

ForkJoinWorkerThread

protected ForkJoinWorkerThread(ThreadGroup group, ForkJoinPool pool, boolean preserveThreadLocals)
Creates a ForkJoinWorkerThread operating in the given thread group and pool, and with the given policy for preserving ThreadLocals.
Parameters:
group - if non-null, the thread group for this thread. Otherwise, the thread group is chosen by the security manager if present, else set to the current thread's thread group.
pool - the pool this thread works in
preserveThreadLocals - if true, always preserve the values of ThreadLocal variables across tasks; otherwise they may be cleared.
Throws:
NullPointerException - if pool is null
Since:
19

ForkJoinWorkerThread

protected ForkJoinWorkerThread(ForkJoinPool pool)
Creates a ForkJoinWorkerThread operating in the given pool.
Parameters:
pool - the pool this thread works in
Throws:
NullPointerException - if pool is null

Method Details

getPool

public ForkJoinPool getPool()
Returns the pool hosting this thread.
Returns:
the pool

getPoolIndex

public int getPoolIndex()
Returns the unique index number of this thread in its pool. The returned value ranges from zero to the maximum number of threads (minus one) that may exist in the pool, and does not change during the lifetime of the thread. This method may be useful for applications that track status or collect results per-worker-thread rather than per-task.
Returns:
the index number

getQueuedTaskCount

public int getQueuedTaskCount()
Returns a (non-negative) estimate of the number of tasks in the thread's queue.
Returns:
a (non-negative) estimate of the number of tasks in the thread's queue
Since:
20
See Also:

onStart

protected void onStart()
Initializes internal state after construction but before processing any tasks. If you override this method, you must invoke super.onStart() at the beginning of the method. Initialization requires care: Most fields must have legal default values, to ensure that attempted accesses from other threads work correctly even before this thread starts processing tasks.

onTermination

protected void onTermination(Throwable exception)
Performs cleanup associated with termination of this worker thread. If you override this method, you must invoke super.onTermination at the end of the overridden method.
Parameters:
exception - the exception causing this thread to abort due to an unrecoverable error, or null if completed normally

run

public void run()
This method is required to be public, but should never be called explicitly. It performs the main run loop to execute ForkJoinTasks.
Specified by:
run in interface Runnable
Overrides:
run in class Thread

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Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
Various third party code in OpenJDK is licensed under different licenses (see Debian package).
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https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/util/concurrent/ForkJoinWorkerThread.html