【名企大厂面试必问的线程池】---Executors工厂创建线程池【方便你我他】知识总结没有最好只有更好

前言：

我们在实际项目开发中，当项目上线后每次发一个请求我们后台就创建一个新线程，首先我们大家应该知道，java是运行在jvm上面的，如果创建的线程特别的多，线程的创建和销毁就需要jvm频繁的进行处理，同时如果我们的发的请求的时间特别短，处理数据很快，但是jvm再处理线程的时间特别长，这就会造成性能上的瓶颈，所以引出我们的线程池工厂类，他是一个接口，同时也是一个规范。下面介绍其各个实现类：

demo练习：

newCachedThreadPool()方法创建无界线程池

无界线程池，大白话就是创建的线程池，存放无穷的线程个数，理论上的Integer.MAX_VALUE的最大值。

实现对象复用效果：

package com.zcw.demo;

import lombok.extern.slf4j.Slf4j;

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

/**
 * @ClassName : MyRunnable
 * @Description : MyRunnable
 * @Author : Zhaocunwei
 * @Date: 2020-04-21 10:45
 */
@Slf4j
public class MyRunnable implements Runnable {
    private String userName;
    public MyRunnable(String userName){
        super();
        this.userName =userName;
    }
    @Override
    public void run(){
        log.info(Thread.currentThread().getName()+"userName="+userName+"begin"+System.currentTimeMillis());
        log.info(Thread.currentThread().getName()+"userName="+userName+"end"+System.currentTimeMillis());
    }

    public static void main(String[] args) throws InterruptedException {
        ExecutorService executorService = Executors.newCachedThreadPool();
        for(int i=0;i<5;i++){
            executorService.execute(new MyRunnable((" "+(i+1))));
        }
        Thread.sleep(1000);
        log.info("===================");
        log.info("===================");
        for(int i=0;i<5;i++){
            executorService.execute(new MyRunnable((""+(i+1))));
        }
    }
}

运行结果：

贴心服务–可以进行定制线程工厂

我们这里可以使用自定义的ThreadFactory接口实现类，实现线程对象的贴心定制

package com.zcw.demo;

import lombok.extern.slf4j.Slf4j;

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

/**
 * @ClassName : MyThreadFactory
 * @Description : 自定义线程工厂类
 * @Author : Zhaocunwei
 * @Date: 2020-04-21 11:01
 */
@Slf4j
public class MyThreadFactory implements ThreadFactory {
    @Override
    public Thread newThread(Runnable runnable){
        Thread thread = new Thread(runnable);
        thread.setName("贴心服务--定制线程池中的线程对象的名称"+Math.random());
        return thread;
    }

    public static void main(String[] args) {
        MyThreadFactory myThreadFactory = new MyThreadFactory();
        ExecutorService executorService = Executors.newCachedThreadPool(myThreadFactory);
        executorService.execute(new Runnable() {
            @Override
            public void run() {
                log.info("进行中"+System.currentTimeMillis()+" "+Thread.currentThread().getName());
            }
        });
    }
    
}

运行结果：

11:05:12.582 [贴心服务--定制线程池中的线程对象的名称0.6235705390619012] INFO com.zcw.demo.MyThreadFactory - 进行中1587438312580 贴心服务--定制线程池中的线程对象的名称0.6235705390619012

现在进行有界线程展示：

顾名思义就是我们创建线程池个数可以指定最大的数量：

newFixedThreadPool(int)

package com.zcw.demo;

import lombok.extern.slf4j.Slf4j;

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

/**
 * @ClassName : MyRunnable
 * @Description : 创建有界线程池
 * @Author : Zhaocunwei
 * @Date: 2020-04-21 11:20
 */
@Slf4j
public class MyRunnable implements Runnable {
    private String userName;
    public MyRunnable(String userName){
        super();
        this.userName =userName;
    }
    @Override
    public void run(){
        log.info(Thread.currentThread().getName()+"userName="+userName+"begin="+System.currentTimeMillis());
        try {
            Thread.sleep(2000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        log.info(Thread.currentThread().getName()+"userName="+userName+"end"+System.currentTimeMillis());
    }

    public static void main(String[] args) {
        ExecutorService executorService = Executors.newFixedThreadPool(3);
        for(int i=0;i<3;i++){
            executorService.execute(new MyRunnable((""+(i+1))));
        }
        for(int i=0;i<3;i++){
            executorService.execute(new MyRunnable((""+(i+1))));
        }
    }
}

展示效果：

最骚的操作：贴心定制定长线程池，私有专属线程池（自己定制）

package com.zcw.demo;

import lombok.extern.slf4j.Slf4j;

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

/**
 * @ClassName : MyThreadFactory
 * @Description :
 * @Author : Zhaocunwei
 * @Date: 2020-04-21 11:37
 */
@Slf4j
public class MyThreadFactory implements ThreadFactory {
    @Override
    public Thread newThread(Runnable r) {
        Thread thread = new Thread(r);
        thread.setName("就是这么酸爽，自己定制对象的名称"+Math.random());
        return thread;
    }

    public static void main(String[] args) {
        MyThreadFactory myThreadFactory = new MyThreadFactory();
        ExecutorService excutorService = Executors.newFixedThreadPool(2,myThreadFactory);
        Runnable runnable = new Runnable() {
            @Override
            public void run() {
                log.info("begin ,,, 进行中..."+System.currentTimeMillis()+" "+Thread.currentThread().getName());
                try {
                    Thread.sleep(3000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                log.info("end 运行..."+System.currentTimeMillis()+""+Thread.currentThread().getName());
            }
        };
        excutorService.execute(runnable);
        excutorService.execute(runnable);
        excutorService.execute(runnable);
    }
}

运行结果：

11:42:41.677 [就是这么酸爽，自己定制对象的名称0.8462610517260408] INFO com.zcw.demo.MyThreadFactory - begin ,,, 进行中...1587440561674 就是这么酸爽，自己定制对象的名称0.8462610517260408
11:42:41.677 [就是这么酸爽，自己定制对象的名称0.9806786749850551] INFO com.zcw.demo.MyThreadFactory - begin ,,, 进行中...1587440561674 就是这么酸爽，自己定制对象的名称0.9806786749850551
11:42:44.681 [就是这么酸爽，自己定制对象的名称0.9806786749850551] INFO com.zcw.demo.MyThreadFactory - end 运行...1587440564681就是这么酸爽，自己定制对象的名称0.9806786749850551
11:42:44.681 [就是这么酸爽，自己定制对象的名称0.8462610517260408] INFO com.zcw.demo.MyThreadFactory - end 运行...1587440564681就是这么酸爽，自己定制对象的名称0.8462610517260408
11:42:44.681 [就是这么酸爽，自己定制对象的名称0.9806786749850551] INFO com.zcw.demo.MyThreadFactory - begin ,,, 进行中...1587440564681 就是这么酸爽，自己定制对象的名称0.9806786749850551
11:42:47.682 [就是这么酸爽，自己定制对象的名称0.9806786749850551] INFO com.zcw.demo.MyThreadFactory - end 运行...1587440567682就是这么酸爽，自己定制对象的名称0.9806786749850551

创建单一线程池模拟MQ，我行我素

package com.zcw.demo;

import lombok.extern.slf4j.Slf4j;

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

/**
 * @ClassName : MyRunnable
 * @Description :
 * @Author : Zhaocunwei
 * @Date: 2020-04-21 11:44
 */
@Slf4j
public class MyRunnable implements Runnable {
    private String userName;

    public MyRunnable(String userName){
        super();
        this.userName =userName;
    }
    @Override
    public void run() {
        log.info(Thread.currentThread().getName()+"username="+userName+"begin"+System.currentTimeMillis());
        try {
            Thread.sleep(2000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        log.info(Thread.currentThread().getName()+"username="+userName+"end"+System.currentTimeMillis());
    }

    public static void main(String[] args) {
        ExecutorService executorService = Executors.newSingleThreadExecutor();
        for(int i=0;i<3;i++){
            executorService.execute(new MyRunnable(""+(i+1)));
        }
    }
}

运行结果：