Java线程池

package com.demo;

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

public class Test {


	public static void main(String[] args) {
		
		System.out.println(Runtime.getRuntime().availableProcessors());
		//testSingleThreadExecutor();
		//testFixedThreadPool();
		//testCachedThreadPool();
	}



	
	/**
	 * 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
	 */
	public static void testFixedThreadPool(){
		//因为线程池大小为3，每个任务输出index后sleep 2秒，所以每两秒打印3个数字。
		//定长线程池的大小最好根据系统资源进行设置。如获取cpu核心数Runtime.getRuntime().availableProcessors()
		ExecutorService fixedThreadPool = Executors.newFixedThreadPool(3);  
		for (int i = 0; i < 10; i++) {  
			final int index = i;  
			fixedThreadPool.execute(new Runnable() {  
				public void run() {  
					try {  
						System.out.println(index);  
						Thread.sleep(2000);  
					} catch (InterruptedException e) {  
						e.printStackTrace();  
					}  
				}  
			});  
		}  
	}

	
	/**
	 * 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，则新建线程。
	 */
	public static void testCachedThreadPool(){
		
		ExecutorService cachedThreadPool = Executors.newCachedThreadPool();  
		for (int i = 0; i < 10; i++) {  
			final int index = i;  
			try {  
				Thread.sleep(index * 1000);  
			} catch (InterruptedException e) {  
				e.printStackTrace();  
			}  
			cachedThreadPool.execute(new Runnable() {  
				public void run() {  
					System.out.println(index);  
				}  
			});  
		}  
	}
	
	
	/**
	 * 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
	 */
	public static void testSingleThreadExecutor(){
		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);  
						Thread.sleep(2000);
					} catch (InterruptedException e) {  
						e.printStackTrace();  
					}  
				}  
			});  
		}  
	}
	
	/**
	 * 创建一个定长线程池，支持定时及周期性任务执行
	 */
	public static void testScheduledThreadPool(){
		
		
		ScheduledExecutorService scheduledThreadPool = Executors.newScheduledThreadPool(5);  
		scheduledThreadPool.schedule(new Runnable() {  
			public void run() {  
				System.out.println("delay 3 seconds");  
			}  
		//延迟3秒执行
		}, 3, TimeUnit.SECONDS); 
		//延迟1秒后每3秒执行一次。
		//}, 3, TimeUnit.SECONDS);  
	}
}