java 线程池-4种

Posted 2020-12-26 supper李狗嗨

java 有四种线程池

1、可缓存线程池

newCachedThreadPool
创建一个可缓存线程池，如果线程池长度超过处理需要，可灵活回收空闲线程，若无可回收

2、定长线程池 可控制最大并发数 

newFixedThreadPool 

创建一个定长线程池，可控制线程最大并发数，超出的线程会在队列中等待。

package com.zyh.controller.test;

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

/**
 * 学习并发编程
 *
 * @author 1101399
 * @CreateDate 2018-7-31 下午2:28:29
 */
public class ThreadTestTwo {

    public static void main(String[] args) {

        // 可缓存线程池
        ExecutorService excutorOne = Executors.newCachedThreadPool();
        // 定长线程池 可控制最大并发数
        ExecutorService excutorTwo = Executors.newFixedThreadPool(2);

        StringBuffer nameOne = new StringBuffer("A");
        excutorOne.submit(new ThreadOne(nameOne));
        StringBuffer nameTwo = new StringBuffer("B");
        excutorOne.submit(new ThreadOne(nameTwo));
        try {
            Thread.sleep(10000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        StringBuffer nameThree = new StringBuffer("C");
        excutorOne.submit(new ThreadOne(nameThree));

        System.out.println("
*******************************************
");
        excutorTwo.submit(new ThreadOne(nameOne));
        excutorTwo.execute(new ThreadOne(nameTwo));
        excutorTwo.submit(new ThreadOne(nameThree));
        System.out.println("
*******************************************
");
    }

    public static class ThreadOne implements Runnable {

        public StringBuffer name;

        public ThreadOne(StringBuffer name) {
            this.name = name;
        }

        @Override
        public void run() {
            for (int i = 0; i < 5; i++) {
                System.out.println("ThreadOne name:" + name + " ID:"
                        + Thread.currentThread().getId());
                try {
                    Thread.sleep(500);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

 

3、单线程化线程池

newSingleThreadExecutor
创建一个单线程化的线程池，它只会用唯一的工作线程来执行任务，保证所有任务按照指定顺序(FIFO, LIFO, 优先级)执行

package com.zyh.controller.test;

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

/**
 * student threads
 *
 * @author 1101399
 * @CreateDate 2018-7-30 下午2:09:01
 */
public class ThreadTestOne {

    public static void main(String[] args) throws InterruptedException {
        final ThreadTest A1 = new ThreadTest("A1");
        final ThreadTest A2 = new ThreadTest("A2");
        final ThreadTest A3 = new ThreadTest("A3");
        A1.start();
        A2.start();
        A1.join();
        A2.join();
        System.out.println("方法一实现多线程");
        if (!A1.isAlive()) {// A1 线程不存在的时候控制台打印一条信息
            System.out.println("A1执行完毕？！");
        }

        final Thread B1 = new Thread(new RunnableTest("B1"));
        B1.start();
        final Thread B2 = new Thread(new RunnableTest("B2"));
        B2.start();
        B1.join();
        B2.join();
        System.out.println("方法二实现多线程");

        /**
         * 直接实现线程的开辟 FIXME
         */
        final Thread C1 = new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    A1.join();
                    A2.join();
                    B1.join();
                    B2.join();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                for (int i = 0; i < 2; i++) {
                    System.out.println("··············");
                }
            }

        });
        C1.start();
        C1.join();
        System.out.println("方法三实现多线程");


        System.out.println("线程池的应用");
        // 线程池的学习&应用
        // 单线程化线程池
        ExecutorService executor = Executors.newSingleThreadExecutor();
        executor.submit(A1);
        executor.submit(A2);
        executor.submit(A3);
        executor.execute(B1);// 这种样子的线程类就是不执行
        executor.execute(A1);
        executor.submit(B1);// 这三种线程的实现方式之前不能 XXX start()启动线程
        executor.submit(B2);// 这三种线程的实现方式之前不能 XXX start()启动线程
        executor.submit(C1);// 这三种线程的实现方式之前不能 XXX start()启动线程
        executor.shutdown();// 停止传入任务

        // executor.shutdownNow();// 停止线程池-对线程池说STOP
        // 会导致线程池中第一个线程的sleep出现sleep interrupted异常
        // 该函数的核心是：它向该线程发起interrupt()请求，而sleep()方法遇到有interrupt()请求时，会抛出InterruptedException()，并继续往下执行
        // 运行到这条语句直接停止线程池-检测线程停止后执行的join()函数毫无意义，不能生效
    }

    /**
     * 继承Thread来实现多线程编程 FIXME
     */
    public static class ThreadTest extends Thread {
        public String nameOne;
        public StringBuffer nameTwo;
        public StringBuilder nameThree;
        private long time;

        // 构造函数
        public ThreadTest(String name) {
            this.nameOne = name;
        }

        // 构造函数
        public ThreadTest(String name, long time) {
            this.nameOne = name;
            this.time = time;
        }

        @Override
        public void run() {
            for (int i = 0; i < 2; i++) {
                System.out.println(this.nameOne + " Thread运行第 " + i + " 次!");
                try {
                    if (this.time != 0) {
                        sleep(this.time + i);
                        System.out.println(this.nameOne + "-time-" + (time + i));
                    } else {
                        // sleep((int) Math.random() * 1000);
                        sleep(50);
                        System.out
                                .println(this.nameOne + "-random-" + (int) (Math.random() * 1000));
                    }
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    /**
     * 实现接口Runnable来实现多线程编程 FIXME
     */
    public static class RunnableTest implements Runnable {

        public String nameOne;
        public StringBuffer nameTwo;
        public StringBuilder nameThree;
        private long time;

        public RunnableTest(String name) {
            this.nameOne = name;
        }

        public RunnableTest(String name, long time) {
            this.nameOne = name;
            this.time = time;
        }

        @Override
        public void run() {
            for (int i = 0; i < 2; i++) {
                System.out.println(this.nameOne + " Runnable运行第 " + i + " 次!");
                try {
                    if (this.time != 0) {
                        Thread.sleep(this.time + i);
                        System.out.println(this.nameOne + "-time-" + (time + i));
                    } else {
                        Thread.sleep((int) Math.random() * 1000);
                        System.out
                                .println(this.nameOne + "-random-" + (int) (Math.random() * 1000));
                    }
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }

    }

}

 

4、定长 定时周期性线程池

newScheduledThreadPool
创建一个定长线程池，支持定时及周期性任务执行