ThreadPoolExecutor.DiscardOldestPolicy

public static class ThreadPoolExecutor.DiscardOldestPolicy
extends Object implements RejectedExecutionHandler

java.lang.Object
↳	java.util.concurrent.ThreadPoolExecutor.DiscardOldestPolicy

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
 }}

Summary

Public constructors
`DiscardOldestPolicy()` Creates a `DiscardOldestPolicy` for the given executor.

Public methods
`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.

Inherited methods

From class


        
          java.lang.Object

`Object`	`clone()` Creates and returns a copy of this object.
`boolean`	`equals(Object obj)` Indicates whether some other object is "equal to" this one.
`void`	`finalize()` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.
`final Class<?>`	`getClass()` Returns the runtime class of this `Object`.
`int`	`hashCode()` Returns a hash code value for the 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(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.
`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()` Causes the current thread to wait until it is awakened, typically by being notified or interrupted.

From interface


        
          java.util.concurrent.RejectedExecutionHandler


      rejectedExecution(Runnable r, ThreadPoolExecutor executor)

Method that may be invoked by a ThreadPoolExecutor when execute cannot accept a task.

Public constructors

DiscardOldestPolicy

Added in API level 1

public DiscardOldestPolicy ()

Creates a DiscardOldestPolicy for the given executor.

Public methods

rejectedExecution

Added in API level 1

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.

Parameters
`r`	`Runnable`: the runnable task requested to be executed
`e`	`ThreadPoolExecutor`: the executor attempting to execute this task