(CSDN迁移) JAVA多线程实现-可控最大并发数线程池(newFixedThreadPool)

上篇文章中介绍了单线程化线程池newSingleThreadExecutor，可控最大并发数线程池(newFixedThreadPool)与其最大的区别是可以通知执行多个线程，可以简单的将newSingleThreadExecutor理解为newFixedThreadPool(1)。例如运行一下两个程序：

单线程化线程池（newSingleThreadExecutor）示例：

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;public class ThreadPoolByNewSingleThreadExecutor {public static void main(String[] args) {
/**
* 单线程化的线程池
*/
ExecutorService singleThreadExecutor = Executors.newSingleThreadExecutor();
for (int i = 0; i < 10; i++) {
final int index = i;
singleThreadExecutor.execute(new Runnable() {
@Override
public void run() {
Thread.currentThread().setName("Thread i = " + index);
System.out.println(Thread.currentThread().getName() + " index = " + index);
try {
Thread.sleep(500);
} catch (InterruptedException e) {
System.out.println("exception");
}
}
});
}
singleThreadExecutor.shutdown();
System.out.println("on the main thread...");}}


可控最大并发数线程池（newFixedThreadPool）示例：

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;public class ThreadPoolByNewFixedThreadPool {
public static void main(String[] args) {ExecutorService newFixedThreadPool = Executors.newFixedThreadPool(3);
for (int i = 0; i < 10; i++) {
final int index = i;
newFixedThreadPool.execute(new Runnable() {
@Override
public void run() {
Thread.currentThread().setName("Thread i = " + index);
System.out.println(Thread.currentThread().getName() + " index = " + index);
try {
Thread.sleep(500);
} catch (InterruptedException e) {
System.out.println("exception");
}
}
});
}
newFixedThreadPool.shutdown();
System.out.println("on the main thread...");
}}


结果从显示上看虽然很相似，但是观察到的执行效果确实完全不一致的，newSingleThreadPool中，只有一个线程，每次输出一行后暂停0.5秒，newFixedThreadPool(3)中可以创建3个线程，一次输出3行后暂停0.5秒（当然是这三个线程都暂停0.5秒）。

动画对比如下所示：