多线程----线程池核心类 ThreadPoolExecutor

60 阅读 0 评论 40 点赞

我是靠谱客的博主风中信封，最近开发中收集的这篇文章主要介绍多线程----线程池核心类 ThreadPoolExecutor，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

ThreadPoolExecutor 4 个组件：

三种不同的实现类：

FixedThreadPool:

SingleThreadExecutor:

CachedThreadPool:

一些线程池的小例子：

CachedThreadPool （创建新线程）:

package com.duoduo.Thread;

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

public class ThreadPoolExecutorTest {
	public static void main(String [] args) {
		ExecutorService cachedThreadPool=Executors.newCachedThreadPool();
		for(int i=0;i<10;i++) {
			final int index=1;
			try {
				Thread.sleep(index*1000);    //线程休息一段时间
			}catch(InterruptedException e) {
				e.printStackTrace();
			}
			cachedThreadPool.execute(new Runnable() {
				public void run() {
					System.out.println(index+"by "+Thread.currentThread().getName());
				}
			});
		}
	}

}

分析：因为线程池为无限大，当执行第二个任务时第一个任务已经完成，会复用执行第一个任务的线程，而不用每次新建线程。

package com.duoduo.Thread;

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

public class ThreadPoolExecutorTest {
	public static void main(String [] args) {
		ExecutorService cachedThreadPool=Executors.newCachedThreadPool();
		for(int i=0;i<10;i++) {
			final int index=1;
			cachedThreadPool.execute(new Runnable() {
				public void run() {
					System.out.println(index+"by "+Thread.currentThread().getName());
				}
			});
		}
	}
}

分析：因为任务并行执行所以需要多个线程同时执行~

FixedThreadPool （固定线程）:

package com.duoduo.Thread;

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

public class ThreadPoolExecutorTest {
	public static void main(String [] args) {
		ExecutorService fixedThreadPool=Executors.newFixedThreadPool(3);  //固定线程数为3
		for(int i=0;i<10;i++) {    //需要执行10个任务
			final int index=1;
			fixedThreadPool.execute(new Runnable() {
				public void run() {
					try {
						System.out.println(index);
						Thread.sleep(2000);    //故每次打印完就睡眠2秒   每两秒打印3个数字
					}catch(InterruptedException e) {
						e.printStackTrace();
					}
				}
			});
		}
	}
}

分析结果：每两秒打印3个数字 3个线程并发打印完事之后睡眠2秒之后继续重复打印。。。。

定长线程池的大小最好根据系统资源进行设置。如Runtime.getRuntime().availableProcessors()

ScheduledThreadPool (延时或定时）:

package com.duoduo.Thread;

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

public class ThreadPoolExecutorTest {
	public static void main(String [] args) {
		ScheduledExecutorService scheduledThreadPool=Executors.newScheduledThreadPool(5);
		scheduledThreadPool.schedule(new Runnable() {
			public void run() {
				System.out.println("delay 3 seconds");
			}
		},3,TimeUnit.SECONDS);
	}
}

效果：等待了3秒之后才打印出屏幕内容~

package com.duoduo.Thread;

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

public class ThreadPoolExecutorTest {
	public static void main(String [] args) {
		ScheduledExecutorService scheduledThreadPool=Executors.newScheduledThreadPool(5);
		scheduledThreadPool.scheduleAtFixedRate(new Runnable(){
			public void run() {
				System.out.println("delay 1 seconds,and execute every 3 seconds"+Thread.currentThread().getName());
			}
		}, 1, 3, TimeUnit.SECONDS);
	}
}

效果：表示延迟1秒后每3秒执行一次。

SingledThreadExecutor (单线程）:

package com.duoduo.Thread;

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

public class ThreadPoolExecutorTest {
	public static void main(String [] args) {
		ExecutorService singleThreadExecutor=Executors.newSingleThreadExecutor();
		for(int i=0;i<10;i++) {
			final int index=i;
			singleThreadExecutor.execute(new Runnable() {
				public void run() {
					try {
						System.out.println(index+"by "+Thread.currentThread().getName());
						Thread.sleep(2000);
					}catch(InterruptedException e) {
						e.printStackTrace();
					}
				}
			});
		}
	}
}