一、例子1：　　　　

 1 package com.cy.test.thread;
 2 
 3 
 4 import java.util.ArrayList;
 5 import java.util.List;
 6 import java.util.concurrent.CountDownLatch;
 7 import java.util.concurrent.ExecutorService;
 8 import java.util.concurrent.Executors;
 9 
10 public class TestMultiThread {
11 
12     /**
13      * n = 核心数*2 + 1
14      */
15     private static ExecutorService pool = Executors.newFixedThreadPool(5);
16 
17     /**
18      * 1.模拟，使用多线程，找到每个学生的老师名字，并且打印出来。
19      * @param args
20      */
21     public static void main(String[] args) {
22         List<String> studentList = new ArrayList<>();
23         studentList.add("zhangsan");
24         studentList.add("lisi");
25         studentList.add("wangwu");
26 
27         try {
28             CountDownLatch latch = new CountDownLatch(studentList.size());
29             doFindTeacher(studentList, latch);
30             latch.await();
31         } catch (InterruptedException e) {
32             e.printStackTrace();
33         }
34 
35         pool.shutdown();
36     }
37 
38     private static void doFindTeacher(List<String> studentList, CountDownLatch latch) {
39         for(String student : studentList){
40             pool.execute(() -> {
41                 System.out.println("开始处理学生:" + student);
42                 //模拟查数据库...等操作，查找学生的老师
43                 try {
44                     Thread.sleep(3000);
45                 } catch (InterruptedException e) {
46                     e.printStackTrace();
47                 }
48                 System.out.println("teacher: " + student + "'s teacher");
49 
50                 latch.countDown();
51             });
52         }
53     }
54 }

console：

开始处理学生:zhangsan
开始处理学生:lisi
开始处理学生:wangwu
teacher: lisi's teacher
teacher: wangwu's teacher
teacher: zhangsan's teacher

执行时间大约3s，多线程并发执行。

 

二、例子2：