多线程--两个线程间的通讯

　　CPU任意切换线程，如果希望 CPU能够有规律的执行，就需要线程间通讯：

this.wait()          当前线程等待

this.notify()        随机唤醒单个线程

this.notifyAll()    唤醒所有线程               

//   为什么定义在object中，因为任意对象都可以成为锁

public class demon1_notify {
    //等待唤醒机制
    public static void main(String[] args) {
        final printer2 p = new printer2();
        new Thread(){
            public void run() {
                while(true){
                    try {
                        p.print1();
                    } catch (InterruptedException e) {
                        
                        e.printStackTrace();
                    }
                }
            }
        }.start();
        new Thread(){
            public void run() { 
                while(true){
                    try {
                        p.print2();
                    } catch (InterruptedException e) {
                        
                        e.printStackTrace();
                    }
                }
            }
        }.start();
    }
}
class printer2{
    private int flag = 1;
    public synchronized void print1() throws InterruptedException{    
        if (flag !=1) {
            this.wait();
        }
        System.out.print("黑");
        System.out.print("马");
        System.out.print("程");
        System.out.print("序");
        System.out.print("员");
        System.out.print("
");
        flag = 2;    
        this.notify();
    }
    public synchronized void print2() throws InterruptedException{    
        if (flag !=2) {
            this.wait();
        }
        System.out.print("传");
        System.out.print("智");
        System.out.print("播");
        System.out.print("客");
        System.out.print("
");
        flag = 1;    
        this.notify();
    }
}

public class demon2_notify2 {

    public static void main(String[] args) {
        final printer3 p = new printer3();
        new Thread(){
            public void run() {
                while(true){
                    try {
                        p.print1();
                    } catch (InterruptedException e) {
                        
                        e.printStackTrace();
                    }
                }
            }
        }.start();
        new Thread(){
            public void run() { 
                while(true){
                    try {
                        p.print2();
                    } catch (InterruptedException e) {
                        
                        e.printStackTrace();
                    }
                }
            }
        }.start();
        new Thread(){
            public void run() {
                while(true){
                    try {
                        p.print3();
                    } catch (InterruptedException e) {
                        
                        e.printStackTrace();
                    }
                }
            }
        }.start();
    }
}
class printer3{
    private int flag = 1;
    public synchronized void print1() throws InterruptedException{    
        while (flag !=1) {
            this.wait();
        }
        System.out.print("黑");
        System.out.print("马");
        System.out.print("程");
        System.out.print("序");
        System.out.print("员");
        System.out.print("
");
        flag = 2;    
        //this.notify();
        this.notifyAll();
    }
    public synchronized void print2() throws InterruptedException{    
        while (flag !=2) {
            this.wait();
        }
        System.out.print("传");
        System.out.print("智");
        System.out.print("播");
        System.out.print("客");
        System.out.print("
");
        flag = 3;    
        this.notifyAll();
    }
    public synchronized void print3() throws InterruptedException{    
        while (flag !=3) {
            this.wait();
        }
        System.out.print("i");
        System.out.print("t");
        System.out.print("h");
        System.out.print("m");
        System.out.print("
");
        flag = 1;    
        this.notifyAll();
    }
}

JDK5之前无法唤醒指定的一个线程，1.5.之后   有互斥锁    ，

　　同步
　　　　* 使用ReentrantLock类的lock()和unlock()方法进行同步

　　通信

　　　　* 使用ReentrantLock类的newCondition()方法可以获取Condition对象
　　　　* 需要等待的时候使用Condition的await()方法, 唤醒的时候用signal()方法
　　　　* 不同的线程使用不同的Condition, 这样就能区分唤醒的时候找哪个线程了

import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.ReentrantLock;

import javax.print.attribute.standard.Sides;

public class demon3_ReentrantLock {

    public static void main(String[] args) {
        final printer4 p4 = new printer4();
        new Thread(){
            public void run() {
                while(true){
                    try {
                        p4.print1();
                    } catch (InterruptedException e) {
                        
                        e.printStackTrace();
                    }
                }
            }
        }.start();
        new Thread(){
            public void run() { 
                while(true){
                    try {
                        p4.print2();
                    } catch (InterruptedException e) {
                        
                        e.printStackTrace();
                    }
                }
            }
        }.start();
        new Thread(){
            public void run() {
                while(true){
                    try {
                        p4.print3();
                    } catch (InterruptedException e) {
                        
                        e.printStackTrace();
                    }
                }
            }
        }.start();
    }
}
class printer4{
    private ReentrantLock r = new ReentrantLock();   // 获取锁
    private Condition c1 = r.newCondition();
    private Condition c2 = r.newCondition();
    private Condition c3 = r.newCondition();
    private int flag = 1;
    public  void print1() throws InterruptedException{
        r.lock();           //唤醒锁
        if (flag !=1) {
            c1.await();
        }
        System.out.print("黑");
        System.out.print("马");
        System.out.print("程");
        System.out.print("序");
        System.out.print("员");
        System.out.print("
");
        flag = 2;    
        c2.signal();           // 唤醒C2
        
        r.unlock();　　　　　　　//   释放锁
    }
    public  void print2() throws InterruptedException{    
        r.lock();
        if (flag !=2) {
            c2.await();
        }
        System.out.print("传");
        System.out.print("智");
        System.out.print("播");
        System.out.print("客");
        System.out.print("
");
        flag = 3;    
        c3.signal();
        r.unlock();
    }
    public  void print3() throws InterruptedException{    
        r.lock();
        if (flag !=3) {
            c3.await();
        }
        System.out.print("i");
        System.out.print("t");
        System.out.print("h");
        System.out.print("m");
        System.out.print("
");
        flag = 1;    
        c1.signal();
        r.unlock();
    }
}