Java, thread pool, threadpoolexecutor

Threadpoolexecutor Definition

public ThreadPoolExecutor(int corePoolSize,                          int maximumPoolSize,                          long keepAliveTime,                          TimeUnit unit,                          BlockingQueue<Runnable> workQueue,                          ThreadFactory threadFactory)

Creates a new ThreadpoolexecutorWith the given initial parameters and default rejected execution handler.

Parameters:

corePoolSize-The number of threads to keep in the pool, even if they are idle.

maximumPoolSize-The maximum number of threads to allow in the pool.

keepAliveTime-When the number of threads is greater than the core, this is the maximum time that excess Idle threads will wait for new tasks before terminating.

unit-The time unit for the KeepAliveTime argument.

workQueue-The queue to use for holding tasks before they are executed. This queue will hold only RunnableTasks submitted by ExecuteMethod.

threadFactory-The factory to use when the executor creates a new thread.

Throws:

IllegalArgumentException-If corepoolsize or KeepAliveTime less than zero, or if maximumpoolsize less than or equal to zero, or if corepoolsize greater than maximumpoolsize.

NullPointerException-If WorkqueueOr ThreadfactoryAre null.

 

Example of threadpoolexecutor

ThreadPoolExecutor threadPool = new ThreadPoolExecutor(2, 4, 3, TimeUnit.SECONDS, 

                new ArrayBlockingQueue<Runnable>(3), 

                new ThreadPoolExecutor.DiscardOldestPolicy()

        );

 

How to add a task to a thread pool

Step 1: Define a task

public class MyTask implements Runnable{

    private String name = null;

    public MyTask(final String name){

        this.name = name;

    }

    @Override

    public void run() {

        // TODO Auto-generated method stub

        System.out.println("My task is " + this.name);

    }

}

 

Step 2: Add a task

Threadpool.exe cute (New mytask ("killing evils ~ "));

 

How is the thread in the thread pool dynamically adjusted?

(1) Under normal circumstances, a maximumcorePoolSizeThreads to execute the task;

(2) If the number of tasks increases,Corepoolsize cannot be done, you canCongestion in workqueue

(3) If the queue is full, try to start a new thread again (Maximumpoolsize-Corepoolsize)

(4) If the number of tasks continues to increase,Workqueue is full,AllMaximumpoolsize cannot be executed.

 

Here are some interesting explanations:

Http://wenku.baidu.com/view/8f4fc14ffe4733687e21aa55.html