线程间通信

一、线程通信方式-共享变量

package com.louis.线程;

import java.util.ArrayList;
import java.util.List;

public class ListAdd1 {


	private volatile static List list = new ArrayList();

	public void add(){
		list.add("bjsxt");
	}
	public int size(){
		return list.size();
	}

	public static void main(String[] args) {

		final ListAdd1 list1 = new ListAdd1();

		Thread t1 = new Thread(new Runnable() {
			@Override
			public void run() {
				try {
					for(int i = 0; i <10; i++){
						list1.add();
						System.out.println("当前线程：" + Thread.currentThread().getName() + "添加了一个元素..");
						Thread.sleep(500);
					}
				} catch (InterruptedException e) {
					e.printStackTrace();
				}
			}
		}, "t1");

		Thread t2 = new Thread(new Runnable() {
			@Override
			public void run() {
				while(true){
					if(list1.size() == 5){
						System.out.println("当前线程收到通知：" + Thread.currentThread().getName() + " list size = 5 线程停止..");
						throw new RuntimeException();
					}
				}
			}
		}, "t2");

		t1.start();
		t2.start();
	}


}

第二个线程一直在循环

线程通信方式-wait/notify
wait（）释放锁，notify不释放锁

package com.louis.线程;

import java.util.ArrayList;
import java.util.List;
import java.util.Queue;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.LinkedBlockingDeque;
import java.util.concurrent.LinkedBlockingQueue;
/**
 * wait notfiy 方法，wait释放锁，notfiy不释放锁
 * @author alienware
 *
 */
public class ListAdd2 {
	private volatile static List list = new ArrayList();

	public void add(){
		list.add("bjsxt");
	}
	public int size(){
		return list.size();
	}

	public static void main(String[] args) {

		final ListAdd2 list2 = new ListAdd2();

		// 1 实例化出来一个 lock
		// 当使用wait 和 notify 的时候 ， 一定要配合着synchronized关键字去使用
		final Object lock = new Object();

//		final CountDownLatch countDownLatch = new CountDownLatch(1);

		Thread t1 = new Thread(new Runnable() {
			@Override
			public void run() {
				try {
					synchronized (lock) {
						for(int i = 0; i <10; i++){
							list2.add();
							System.out.println("当前线程：" + Thread.currentThread().getName() + "添加了一个元素..");
							Thread.sleep(500);
							if(list2.size() == 5){
								System.out.println("已经发出通知..");
//								countDownLatch.countDown();
								lock.notify();
							}
						}
					}
				} catch (InterruptedException e) {
					e.printStackTrace();
				}

			}
		}, "t1");

		Thread t2 = new Thread(new Runnable() {
			@Override
			public void run() {
				synchronized (lock) {
					if(list2.size() != 5){
						try {
							//System.out.println("t2进入...");
							lock.wait();
//							countDownLatch.await();
						} catch (InterruptedException e) {
							e.printStackTrace();
						}
					}
					System.out.println("当前线程：" + Thread.currentThread().getName() + "收到通知线程停止..");
					throw new RuntimeException();
				}
			}
		}, "t2");

		t2.start();
		t1.start();

	}

}

缺点：notify不会释放锁，在notify后到wait执行完这段时间是一直占有锁的。
改进：countDownLatch

线程间通信-countDownLatch

public class ListAdd2 {
	private volatile static List list = new ArrayList();

	public void add(){
		list.add("bjsxt");
	}
	public int size(){
		return list.size();
	}

	public static void main(String[] args) {

		final ListAdd2 list2 = new ListAdd2();

		// 1 实例化出来一个 lock
		// 当使用wait 和 notify 的时候 ， 一定要配合着synchronized关键字去使用
		//final Object lock = new Object();

		final CountDownLatch countDownLatch = new CountDownLatch(1);

		Thread t1 = new Thread(new Runnable() {
			@Override
			public void run() {
				try {
					//synchronized (lock) {
						for(int i = 0; i <10; i++){
							list2.add();
							System.out.println("当前线程：" + Thread.currentThread().getName() + "添加了一个元素..");
							Thread.sleep(500);
							if(list2.size() == 5){
								System.out.println("已经发出通知..");
								countDownLatch.countDown();
								//lock.notify();
							}
						}
					//}
				} catch (InterruptedException e) {
					e.printStackTrace();
				}

			}
		}, "t1");

		Thread t2 = new Thread(new Runnable() {
			@Override
			public void run() {
				//synchronized (lock) {
					if(list2.size() != 5){
						try {
							//System.out.println("t2进入...");
							//lock.wait();
							countDownLatch.await();
						} catch (InterruptedException e) {
							e.printStackTrace();
						}
					}
					System.out.println("当前线程：" + Thread.currentThread().getName() + "收到通知线程停止..");
					throw new RuntimeException();
				//}
			}
		}, "t2");

		t2.start();
		t1.start();

	}

}

可以立即受到通知。