我在做Thinking In Java第四版最后一章第三个练习
我写的是：
- Java code
import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;public class Ex3{ public static void main(String[] args) { System.out.println("------Cached Pool------"); ExecutorService execCached = Executors.newCachedThreadPool(); execCached.execute(new Imex31()); execCached.execute(new Imex32()); execCached.execute(new Imex33()); execCached.shutdown(); System.out.println("------Fixed Pool------"); ExecutorService execFixed = Executors.newFixedThreadPool(3); execFixed.execute(new Imex31()); execFixed.execute(new Imex32()); execFixed.execute(new Imex33()); execFixed.shutdown(); System.out.println("------Single Thread------"); ExecutorService execSingle = Executors.newSingleThreadExecutor(); execSingle.execute(new Imex31()); execSingle.execute(new Imex32()); execSingle.execute(new Imex33()); execSingle.shutdown(); /*Thread t1 = new Thread(new Imex31()); Thread t2 = new Thread(new Imex32()); Thread t3 = new Thread(new Imex33()); t1.start(); t2.start(); t3.start();*/ }}class Imex31 implements Runnable{ public Imex31() { System.out.println("Constructor 1 begin"); } public void run() { for (int i = 1; i < 4; i++) { System.out.println("In the run ex1 " + i); Thread.yield(); } System.out.println("ex1 complete"); return; }}class Imex32 implements Runnable{ public Imex32() { System.out.println("Constructor 2 begin"); } public void run() { for (int i = 1; i < 4; i++) { System.out.println("In the run ex2 " + i); Thread.yield(); } System.out.println("ex2 complete"); return; }}class Imex33 implements Runnable{ public Imex33() { System.out.println("Constructor 3 begin"); } public void run() { for (int i = 1; i < 4; i++) { System.out.println("In the run ex3 " + i); Thread.yield(); } System.out.println("ex3 complete"); return; }}奇怪的是输出显示execFixed那几个线程没有shutdown就开始execSingle了，这是怎么回事呢？
谢谢先！！
------解决方案--------------------
你三个线程池之间并没有什么关系，三个线程池 每个分别处理三个不同的任务。
你的主线程是 main 方法 ，
ExecutorService execCached = Executors.newCachedThreadPool();
execCached.execute(new Imex31());
execCached.execute(new Imex32());
execCached.execute(new Imex33());
execCached.shutdown();
System.out.println("------Fixed Pool------");
ExecutorService execFixed = Executors.newFixedThreadPool(3);
execFixed.execute(new Imex31());
execFixed.execute(new Imex32());
execFixed.execute(new Imex33());
execFixed.shutdown();
System.out.println("------Single Thread------");
ExecutorService execSingle = Executors.newSingleThreadExecutor();
execSingle.execute(new Imex31());
execSingle.execute(new Imex32());
execSingle.execute(new Imex33());
execSingle.shutdown();
你在线程池上调用 shuntdown 是告诉线程池 ，在任务完成的时候结束线程而已。
再说 在线程池上面 shutdown 线程又不会阻塞， 那么后面的语句当然可以执行了啊。
你可以 在每个线程池开始后 也就是在 shutdown 后面加上 一句 TimeUnit.Second.sleep(5)； 睡几秒过后等你线程池的任务任务执行完毕后在开始下一个线程池。
建议在把线程池 的API 仔细看看吧。
楼上说的家 synchronized 那是肯定都不对的。 因为根本不涉及到任何同步。