Java线程池表示一组正在等待作业并重复使用多次的工作线程。
在线程池的情况下，创建一组固定大小的线程。 来自线程池中的线程被拉出并由服务提供者分配作业。 完成作业后，线程再次包含在线程池中。
Java线程池的优点
提供了更好的性能，因为不需要重新创建新线程，所以节省了时间。
实时使用
在Servlet和JSP中使用，容器创建一个线程池来处理请求。
Java线程池的示例
下面来看看使用ExecutorService和Executors的java线程池的简单示例。
文件: WorkerThread.java
package com.yiibai;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
class WorkerThread implements Runnable {
private String message;
public WorkerThread(String s) {
this.message = s;
}
public void run() {
System.out.println(Thread.currentThread().getName() + " (Start) message = " + message);
processmessage();// call processmessage method that sleeps the thread for 2 seconds
System.out.println(Thread.currentThread().getName() + " (End)");// prints thread name
}
private void processmessage() {
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
文件: WorkerThread.java
package com.yiibai;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class TestThreadPool {
public static void main(String[] args) {
ExecutorService executor = Executors.newFixedThreadPool(5);//creating a pool of 5 threads
for (int i = 0; i < 10; i++) {
Runnable worker = new WorkerThread("" + i);
executor.execute(worker);//calling execute method of ExecutorService
}
executor.shutdown();
while (!executor.isTerminated()) { }
System.out.println("Finished all threads");
}
}
执行上面示例代码，得到以下结果：
pool-1-thread-2 (Start) message = 1
pool-1-thread-4 (Start) message = 3
pool-1-thread-5 (Start) message = 4
pool-1-thread-3 (Start) message = 2
pool-1-thread-1 (Start) message = 0
pool-1-thread-5 (End)
pool-1-thread-2 (End)
pool-1-thread-4 (End)
pool-1-thread-1 (End)
pool-1-thread-3 (End)
pool-1-thread-1 (Start) message = 6
pool-1-thread-3 (Start) message = 7
pool-1-thread-2 (Start) message = 5
pool-1-thread-4 (Start) message = 8
pool-1-thread-5 (Start) message = 9
pool-1-thread-3 (End)
pool-1-thread-5 (End)
pool-1-thread-4 (End)
pool-1-thread-1 (End)
pool-1-thread-2 (End)
Finished all threads
