Class ThreadPoolExecutor.DiscardOldestPolicy

java.lang.Object

java.util.concurrent.ThreadPoolExecutor.DiscardOldestPolicy

All Implemented Interfaces:

RejectedExecutionHandler

Enclosing class:

ThreadPoolExecutor

public static class ThreadPoolExecutor.DiscardOldestPolicy
extends Object
implements RejectedExecutionHandler

A handler for rejected tasks that discards the oldest unhandled request and then retries execute, unless the executor is shut down, in which case the task is discarded. This policy is rarely useful in cases where other threads may be waiting for tasks to terminate, or failures must be recorded. Instead consider using a handler of the form:

new RejectedExecutionHandler() {
  public void rejectedExecution(Runnable r, ThreadPoolExecutor e) {
    Runnable dropped = e.getQueue().poll();
    if (dropped instanceof Future<?>) {
      ((Future<?>)dropped).cancel(false);
      // also consider logging the failure
    }
    e.execute(r);  // retry
}}

Since:

1.5

Constructor Summary

Constructors

Constructor	Description
DiscardOldestPolicy()	Creates a DiscardOldestPolicy for the given executor.

Method Summary

Modifier and Type	Method	Description
void	rejectedExecution(Runnable r, ThreadPoolExecutor e)	Obtains and ignores the next task that the executor would otherwise execute, if one is immediately available, and then retries execution of task r, unless the executor is shut down, in which case task r is instead discarded.

Methods declared in class Object

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

Modifier and Type	Method	Description
protected Object	clone()	Creates and returns a copy of this object.
boolean	equals(Object obj)	Indicates whether some other object is "equal to" this one.
protected void	finalize()	Deprecated, for removal: This API element is subject to removal in a future version. Finalization is deprecated and subject to removal in a future release.
final Class<?>	getClass()	Returns the runtime class of this Object.
int	hashCode()	Returns a hash code value for this object.
final void	notify()	Wakes up a single thread that is waiting on this object's monitor.
final void	notifyAll()	Wakes up all threads that are waiting on this object's monitor.
String	toString()	Returns a string representation of the object.
final void	wait()	Causes the current thread to wait until it is awakened, typically by being notified or interrupted.
final void	wait(long timeoutMillis)	Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
final void	wait(long timeoutMillis, int nanos)	Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.

Constructor Details

DiscardOldestPolicy

public DiscardOldestPolicy()

Creates a DiscardOldestPolicy for the given executor.

Method Details

rejectedExecution

public void rejectedExecution(Runnable r,
 ThreadPoolExecutor e)

Obtains and ignores the next task that the executor would otherwise execute, if one is immediately available, and then retries execution of task r, unless the executor is shut down, in which case task r is instead discarded.

Specified by:

rejectedExecution in interface RejectedExecutionHandler

Parameters:

r - the runnable task requested to be executed

e - the executor attempting to execute this task