多线程效率问题

 

package ThreadTest;

public class ThreadTest3 {
	public static void main(String args[]){
        MyThread mt = new MyThread() ;    // 定义线程对象
   
        Thread t1 = new Thread(mt) ;    // 定义Thread对象
//        Thread t2 = new Thread(mt) ;    // 定义Thread对象
//        Thread t3 = new Thread(mt) ;    // 定义Thread对象
        t1.start() ;
//        t2.start() ;
//        t3.start() ;
    }
}

class MyThread implements Runnable{
    private int ticket = 5 ;    // 假设一共有5张票
    private long start = 0;
    public void run(){
    	sale();
    }
    private synchronized void sale(){
    	if (start == 0){
    		start = System.currentTimeMillis();
    	}
    	 while(ticket>0){
             try {
                 Thread.sleep(300);
             } catch (InterruptedException e) {
                 // TODO Auto-generated catch block
                 e.printStackTrace();
             }
             System.out.println("卖票：ticket = " + ticket-- );
         }
    	 if (ticket == 0){
    	      System.out.println("cost" + (System.currentTimeMillis() - start));
    	 }
    }
}

 

cost1515

 

在线程同步下，使用多线程和单线程时间都在1515ms之间，多线程效率并不比单线程效率高

 

在线程不同步下，使用多线程时间都在906ms之间，多线程效率比单线程效率高

 

 

package ThreadTest;

public class ThreadTest3 {
	public static void main(String args[]){
        MyThread mt = new MyThread() ;    // 定义线程对象
   
        Thread t1 = new Thread(mt) ;    // 定义Thread对象
        Thread t2 = new Thread(mt) ;    // 定义Thread对象
        Thread t3 = new Thread(mt) ;    // 定义Thread对象
        t1.start() ;
        t2.start() ;
        t3.start() ;
    }
}

class MyThread implements Runnable{
    private int ticket = 5 ;    // 假设一共有5张票
    private long start = 0;
    public void run(){
    	sale();
    }
//    private synchronized void sale(){
    private void sale(){
    	if (start == 0){
    		start = System.currentTimeMillis();
    	    System.out.println("cost");
    	}
    	 while(ticket>0){
             try {
                 Thread.sleep(300);
             } catch (InterruptedException e) {
                 // TODO Auto-generated catch block
                 e.printStackTrace();
             }
             System.out.println("卖票：ticket = " + ticket-- );
         }
    	 if (ticket <= 0){
    	      System.out.println("cost" + (System.currentTimeMillis() - start));
    	 }
    }
}

 

 

cost

卖票：ticket = 5

卖票：ticket = 5

卖票：ticket = 4

卖票：ticket = 3

卖票：ticket = 2

卖票：ticket = 3

卖票：ticket = 1

cost907

卖票：ticket = 0

卖票：ticket = 1

cost907

cost907

评论

1 楼 tomfish88 2012-05-09  

你用5条数据太少了，你用50000条你就看出差距了