可以通过调用Executors类的static newFixedThreadPool()方法获得一个固定线程池。
语法
ExecutorService fixedPool = Executors.newFixedThreadPool(2);
其中，
- 最多
2个线程将处于活动状态。 - 如果提交了两个以上的线程，那么它们将保持在队列中，直到线程可用。
- 如果一个线程由于执行关闭期间的失败而终止，则执行器尚未被调用，则创建一个新线程。
- 线程会一直存在，直到池关闭。
示例
以下TestThread程序显示在线程环境中使用newFixedThreadPool方法。
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
public class TestThread {
public static void main(final String[] arguments) throws InterruptedException {
ExecutorService executor = Executors.newFixedThreadPool(2);
// Cast the object to its class type
ThreadPoolExecutor pool = (ThreadPoolExecutor) executor;
//Stats before tasks execution
System.out.println("Core threads: " + pool.getCorePoolSize());
System.out.println("Largest executions: "
+ pool.getLargestPoolSize());
System.out.println("Maximum allowed threads: "
+ pool.getMaximumPoolSize());
System.out.println("Current threads in pool: "
+ pool.getPoolSize());
System.out.println("Currently executing threads: "
+ pool.getActiveCount());
System.out.println("Total number of threads(ever scheduled): "
+ pool.getTaskCount());
executor.submit(new Task());
executor.submit(new Task());
//Stats after tasks execution
System.out.println("Core threads: " + pool.getCorePoolSize());
System.out.println("Largest executions: "
+ pool.getLargestPoolSize());
System.out.println("Maximum allowed threads: "
+ pool.getMaximumPoolSize());
System.out.println("Current threads in pool: "
+ pool.getPoolSize());
System.out.println("Currently executing threads: "
+ pool.getActiveCount());
System.out.println("Total number of threads(ever scheduled): "
+ pool.getTaskCount());
executor.shutdown();
}
static class Task implements Runnable {
public void run() {
try {
Long duration = (long) (Math.random() * 5);
System.out.println("Running Task! Thread Name: " + Thread.currentThread().getName());
TimeUnit.SECONDS.sleep(duration);
System.out.println("Task Completed! Thread Name: "+ Thread.currentThread().getName());
}
catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
这将产生以下结果 -
Core threads: 2
Largest executions: 0
Maximum allowed threads: 2
Current threads in pool: 0
Currently executing threads: 0
Total number of threads(ever scheduled): 0
Core threads: 2
Largest executions: 2
Maximum allowed threads: 2
Current threads in pool: 2
Currently executing threads: 1
Total number of threads(ever scheduled): 1
Running Task! Thread Name: pool-1-thread-1
Running Task! Thread Name: pool-1-thread-2
Task Completed! Thread Name: pool-1-thread-1
Task Completed! Thread Name: pool-1-thread-2
