Java newFixedThreadPool线程池实例及讲解

闲话不多说，直接上代码。

<span style="font-size:18px;">import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class MyThreadPool {

private ExecutorService exe;
private static final int POOL_SIZE = 4;

public MyThreadPool() {
exe = Executors.newFixedThreadPool(POOL_SIZE);
}

public void doTask() {
int i = 0;
while (i < 50) {
exe.execute(new MyThread(i, exe));
i++;
}
}

class MyThread implements Runnable
{
int id;
ExecutorService exe;
MyThread(int id, ExecutorService exe) {
this.exe = exe;
this.id = id;
}
public void run() {
System.out.println(id + "start");
try {
Thread.sleep(5000L);
} catch (InterruptedException e) {
e.printStackTrace();
}

System.out.println(id + "pass 5 second");
System.out.println("exe info:" + exe.toString());
try {
Thread.sleep(5000L);
} catch (InterruptedException e) {
e.printStackTrace();
}

System.out.println(id + "end");
}
}

public static void main(String[] args) {
new MyThreadPool().doTask();
}
}</span>

MyThreadPool为线程池管理类

MyThread为实际需要运行的线程类

运行log如下（一小部分）：

<span style="font-size:18px;">1start
2start
3start
0start
2pass 5 second
exe info:java.util.concurrent.ThreadPoolExecutor@39890510[Running, pool size = 4, active threads = 4, queued tasks = 46, completed tasks = 0]
0pass 5 second
exe info:java.util.concurrent.ThreadPoolExecutor@39890510[Running, pool size = 4, active threads = 4, queued tasks = 46, completed tasks = 0]
3pass 5 second
exe info:java.util.concurrent.ThreadPoolExecutor@39890510[Running, pool size = 4, active threads = 4, queued tasks = 46, completed tasks = 0]
1pass 5 second
exe info:java.util.concurrent.ThreadPoolExecutor@39890510[Running, pool size = 4, active threads = 4, queued tasks = 46, completed tasks = 0]
2end
4start
0end
5start
3end
6start
1end
7start
</span>

可以看到当前在运行的线程只有前4个，队列中有46个任务在等待

只要有一个线程结束立即就会执行队列中的下一个线程