线程：一道线程的面试题

线程1循环3次，线程2循环6次，线程3循环9次，接着又回到线程1循环3次，线程2循环6次，线程3循环9次...如此循环50次

package ch03;

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

public class ConditionCommunication {

    public static void main(String[] args) {
        final Business business = new Business();
        //线程1
        new Thread(new Runnable() {
            
            @Override
            public void run() {
                for(int i=1; i<=50; i++){
                    business.sub1(i);
                }
            }
        }).start();
        
        //线程2
        new Thread(new Runnable() {
            
            @Override
            public void run() {
                for(int i=1; i<=50; i++){
                    business.sub2(i);
                }
            }
        }).start();
        
        //主线程
        for(int i=1; i<=50; i++){
            business.sub3(i);
        }
        
    }

}

/**
 * 将相似的业务代码封装在同一个类中
 *
 */
class Business{
    
    private Lock lock = new ReentrantLock();
    //标志位，1：表示线程1执行；2表示线程2执行；3表示线程3执行
    volatile int flag = 1; 
    //条件
    private Condition condition1 = lock.newCondition();
    private Condition condition2 = lock.newCondition();
    private Condition condition3 = lock.newCondition();
    
    public void sub1(int i){
        lock.lock();
        
        while(flag != 1){
            try {
                condition1.await(); //线程1等待
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        for(int j=1; j<=3; j++){
            System.out.println("sub1 "+j+",loop "+i);
        }
        flag = 2;
        //唤醒线程2
        condition2.signal();
        
        lock.unlock();
    }
    
    public void sub2(int i){
        lock.lock();
        
        while(flag != 2){
            try {
                condition2.await();    //线程2等待
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        for(int j=1; j<=6; j++){
            System.out.println("sub2  执行"+j+"次，外部循环"+i);
        }
        flag = 3;
        //唤醒线程3
        condition3.signal();
        
        lock.unlock();
    }
    
    public void sub3(int i){
        lock.lock();
        
        while(flag != 3){
            try {
                condition3.await();    //线程3等待
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        for(int j=1; j<=9;j++){
            System.out.println("sub3  执行"+j+"次，外部循环............"+i);
        }
        flag = 1;
        //唤醒线程1
        condition1.signal();
        
        lock.unlock();
    }
    
}