学习过程观看视频：[狂神说Java]
https://www.bilibili.com/video/BV1B7411L7tE?p=13
欢迎大家支持噢，很良心的老师了！

三大方法，代码示例

1、newSingleThreadExecutor

package com.add;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/**
 * Created by zjl
 * 2020/11/25
 **/
public class ExecutorsTest {
    
    
    public static void main(String[] args) {
    
    
        ExecutorService executorService = Executors.newSingleThreadExecutor();   //单个线程
//        ExecutorService executorService = Executors.newFixedThreadPool(5);     //固定大小的线程池
//        ExecutorService executorService = Executors.newCachedThreadPool();     //可伸缩的，遇强则强，遇弱则弱

        try {
    
    
            for (int i = 0; i < 10; i++) {
    
    
                // 使用了线程池之后，使用线程池来创建线程
                executorService.execute(()->{
    
    
                    System.out.println(Thread.currentThread().getName() + "is ok");
                });
            }
        } catch (Exception e) {
    
    
            e.printStackTrace();
        } finally {
    
    
            // 线程池用完，程序结束，关闭线程池
            executorService.shutdown();
        }
    }
}

运行结果：

pool-1-thread-1is ok
pool-1-thread-1is ok
pool-1-thread-1is ok
pool-1-thread-1is ok
pool-1-thread-1is ok
pool-1-thread-1is ok
pool-1-thread-1is ok
pool-1-thread-1is ok
pool-1-thread-1is ok
pool-1-thread-1is ok

Process finished with exit code 0

2、newFixedThreadPool

package com.add;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/**
 * Created by zjl
 * 2020/11/25
 **/
public class ExecutorsTest {
    
    
    public static void main(String[] args) {
    
    
//        ExecutorService executorService = Executors.newSingleThreadExecutor();   //单个线程
        ExecutorService executorService = Executors.newFixedThreadPool(5);     //固定大小的线程池
//        ExecutorService executorService = Executors.newCachedThreadPool();     //可伸缩的，遇强则强，遇弱则弱

        try {
    
    
            for (int i = 0; i < 10; i++) {
    
    
                // 使用了线程池之后，使用线程池来创建线程
                executorService.execute(()->{
    
    
                    System.out.println(Thread.currentThread().getName() + "======》is ok");
                });
            }
        } catch (Exception e) {
    
    
            e.printStackTrace();
        } finally {
    
    
            // 线程池用完，程序结束，关闭线程池
            executorService.shutdown();
        }
    }
}

运行结果：
我们可以看到，最大可以有5个线程共同执行。

3、newCachedThreadPool

package com.add;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/**
 * Created by zjl
 * 2020/11/25
 **/
public class ExecutorsTest {
    
    
    public static void main(String[] args) {
    
    
//        ExecutorService executorService = Executors.newSingleThreadExecutor();   //单个线程
//        ExecutorService executorService = Executors.newFixedThreadPool(5);     //固定大小的线程池
        ExecutorService executorService = Executors.newCachedThreadPool();     //可伸缩的，遇强则强，遇弱则弱

        try {
    
    
            for (int i = 0; i < 10; i++) {
    
    
                // 使用了线程池之后，使用线程池来创建线程
                executorService.execute(()->{
    
    
                    System.out.println(Thread.currentThread().getName() + "======》is ok");
                });
            }
        } catch (Exception e) {
    
    
            e.printStackTrace();
        } finally {
    
    
            // 线程池用完，程序结束，关闭线程池
            executorService.shutdown();
        }
    }
}

执行结果：
我们可以看到，线程池会自动改变大小。