序文
Githubの：https://github.com/yihonglei/thinking-in-concurrent
戦略中止
新しいタスクの提出は、例外は呼び出し側によって捕獲されたときにデフォルトポリシー、直接投げRejectedExecutionExceptionはチェック。
new ThreadPoolExecutor.AbortPolicy()/**
* A handler for rejected tasks that throws a
* {@code RejectedExecutionException}.
*/
public static class AbortPolicy implements RejectedExecutionHandler {
/**
* Creates an {@code AbortPolicy}.
*/
public AbortPolicy() { }
/**
* Always throws RejectedExecutionException.
*
* @param r the runnable task requested to be executed
* @param e the executor attempting to execute this task
* @throws RejectedExecutionException always
*/
public void rejectedExecution(Runnable r, ThreadPoolExecutor e) {
throw new RejectedExecutionException("Task " + r.toString() +
" rejected from " +
e.toString());
}
}二CallerRuns戦略
メカニズムを調整するには、いないタスクを放棄するためにスローされていませんが、いくつかのタスクは、呼び出し側にフォールバックします。これは、スレッドプール内のスレッドで新しいタスクを実行していません、
しかし、実装を担当して新しいタスクの呼び出しexectorスレッド、ある曲を、実行します。
new ThreadPoolExecutor.CallerRunsPolicy()/**
* A handler for rejected tasks that runs the rejected task
* directly in the calling thread of the {@code execute} method,
* unless the executor has been shut down, in which case the task
* is discarded.
*/
public static class CallerRunsPolicy implements RejectedExecutionHandler {
/**
* Creates a {@code CallerRunsPolicy}.
*/
public CallerRunsPolicy() { }
/**
* Executes task r in the caller's thread, unless the executor
* has been shut down, in which case the task is discarded.
*
* @param r the runnable task requested to be executed
* @param e the executor attempting to execute this task
*/
public void rejectedExecution(Runnable r, ThreadPoolExecutor e) {
if (!e.isShutdown()) {
r.run();
}
}
}3つの戦略を破棄
新しいタスクの提出は断念されました。
new ThreadPoolExecutor.DiscardPolicy()/**
* A handler for rejected tasks that silently discards the
* rejected task.
*/
public static class DiscardPolicy implements RejectedExecutionHandler {
/**
* Creates a {@code DiscardPolicy}.
*/
public DiscardPolicy() { }
/**
* Does nothing, which has the effect of discarding task r.
*
* @param r the runnable task requested to be executed
* @param e the executor attempting to execute this task
*/
public void rejectedExecution(Runnable r, ThreadPoolExecutor e) {
}
}四DiscardOldest戦略
キューは、「チームのヘッド、」タスク、および新しいタスクを提出しようとしています。タスクのヘッドは、（作業キューのプライオリティキューのシーンに適していない）に廃棄されています
new ThreadPoolExecutor.DiscardOldestPolicy()/**
* A handler for rejected tasks that discards the oldest unhandled
* request and then retries {@code execute}, unless the executor
* is shut down, in which case the task is discarded.
*/
public static class DiscardOldestPolicy implements RejectedExecutionHandler {
/**
* Creates a {@code DiscardOldestPolicy} for the given executor.
*/
public DiscardOldestPolicy() { }
/**
* 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.
*
* @param r the runnable task requested to be executed
* @param e the executor attempting to execute this task
*/
public void rejectedExecution(Runnable r, ThreadPoolExecutor e) {
if (!e.isShutdown()) {
e.getQueue().poll();
e.execute(r);
}
}
}ファイブカスタム飽和処理戦略
import java.util.concurrent.RejectedExecutionHandler;
import java.util.concurrent.ThreadPoolExecutor;
/**
* 循环处理,当队列有空位时,该任务进入队列，等待线程池处理
*/
public class CustomRejectedExecutionHandler implements RejectedExecutionHandler {
public void rejectedExecution(Runnable r, ThreadPoolExecutor executor) {
try {
executor.getQueue().put(r);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
