Java上路10-线程通信

       需求：超市的销售部和采购部同时对仓库进行使用，库存达到100，销售部就卖货，库存小于1000就必须进货。开始运营超市。

代码：

class Stock     //库存{       public int count=0;      //库存数量} class Procure implements Runnable  //采购{       private Stock sk;        Procure(Stock sk)       {              this.sk=sk;       }        public void run()       {              while (true)              {                     synchronized (sk)                     {                            if(sk.count<1000)                            {                                   sk.count +=100;                                   System.out.println("存货100，余量 "+sk.count);                            }                     }              }       }} class Sales implements Runnable      //销售{       private Stock sk;        Sales (Stock sk)       {              this.sk=sk;       }        public void run()       {              while (true)              {                     synchronized (sk)                     {                            if(sk.count>=100)                            {                            sk.count-= 100;                            System.out.println("出货100，余 "+sk.count);                            }                     }              }       }} class ThreadCommun{       public static void main(String[] args)       {              Stock sk=new Stock();               Procure pr=new Procure(sk);              Sales sa=new Sales(sk);               new Thread(pr).start();              new Thread(sa).start();       }}   

       现在要求，销售部卖出100，采购部就得进货100；采购部一进货，销售部就得卖；交替执行。我们设置一个销售开关，如果开，则采购等待，销售卖货，卖出后关闭开关；如果关，则销售等待，采购进货，进货后打开开关。

        如果采购部和销售部都有多个员工同步进行工作。如何做到采购100，销售100？

class Stock     //库存{       private int count=100;       //库存数量       public boolean sale=true;   //销售        public synchronized void set(int count)       {              while (sale)                     try{this.wait();}catch(Exceptione){}               this.count += count;              System.out.println("加入了 "+count+"，余"+this.count);               sale=true;              this.notifyAll();       }       public synchronized void show()       {              while (!sale)                     try{this.wait();}catch(Exceptione){}               count -= 100;              System.out.println("销售 100，余"+count);               sale=false;              this.notifyAll();       }} class Procure implements Runnable  //采购{       private Stock sk;        Procure(Stock sk)       {              this.sk=sk;       }        public void run()       {              while (true)              {                     sk.set(100);              }       }} class Sales implements Runnable      //销售{       private Stock sk;        Sales (Stock sk)       {              this.sk=sk;       }        public void run()       {              while (true)              {                     sk.show();              }       }} class ThreadCommun{       public static void main(String[] args)       {              Stock sk=new Stock();       //仓库               new Thread(new Procure(sk)).start();              new Thread(new Procure(sk)).start();              //new Thread(new Procure(sk)).start();              new Thread(new Sales(sk)).start();              new Thread(new Sales(sk)).start();              new Thread(new Sales(sk)).start();       }}   

       JDK1.5中提供了另一套类实现同步。java.util.concurrent.locks，其中有个接口Lock。他可以为不同的线程指定不同的通道，并且所有线程是同步的。

import java.util.concurrent.locks.*;//导入这个类包class LockDemo {public static void main(String[] args) {Stock sk=new Stock();new Thread(new Procure(sk)).start();new Thread(new Sales(sk)).start();new Thread(new Procure(sk)).start();new Thread(new Sales(sk)).start();}}class Procure implements Runnable//采购{private Stock sk;Procure(Stock sk){this.sk=sk;}public void run(){while (true){try{sk.inner(100);}catch(InterruptedException e){}}}}class Sales implements Runnable//销售{private Stock sk;Sales (Stock sk){this.sk=sk;}public void run(){while (true){try{sk.outer();}catch(InterruptedException e){}}}}class Stock//操作库存{private int count=100;//余量private boolean flag=true;//销售private Lock lock=new ReentrantLock();private Condition condition_in =lock.newCondition();private Condition condition_out =lock.newCondition();void inner (int count) throws InterruptedException{lock.lock();try{while (flag)condition_in.await();this.count+=count;System.out.println(Thread.currentThread().getName()+"加入了 "+count+"，余 "+this.count);flag=true;condition_out.signal();}finally{lock.unlock();}}void outer () throws InterruptedException{lock.lock();try{while (!flag)condition_out.await();count -= 100;System.out.println(Thread.currentThread().getName()+"销售 100，余"+count);flag=false;condition_in.signal();}finally{lock.unlock();}}}

        针对线程同时处于冻结状态，Java提供interrupt方法强制线程进入运行状态。

class StopThreadDemo {public static void main(String[] args) {StopThread st=new StopThread();Thread t1=new Thread(st);Thread t2=new Thread(st);t1.start();t2.start();int num=0;while (true){if (num++==60){t1.interrupt();//强制唤醒线程t2.interrupt();break;}System.out.println("main..."+num);}}}class StopThread implements Runnable{private boolean flag=true;public synchronized void run(){while (flag){try{wait();}catch (InterruptedException e){System.out.println(Thread.currentThread().getName()+"...Exception");flag=false;//结束循环，完成run，线程终止}System.out.println(Thread.currentThread().getName()+"...run");}}}