线程问题-单例的属性变量

 

1  单例对象 

 

/**
 * @Title:SingleEntity
 * @Author Tony
 * @Date: 2014年6月20日 下午2:20:25
 * @Description:  验证 单例对象的属性 在多线程中访问时不安全的 
 */
public class SingleEntity {

	private static  SingleEntity  singleEntity  ;
	private static String lock="" ; //锁对象不能为空 
	public  static String temp; 
	//私有的构造函数 
	private SingleEntity(){
		
	}
	
	public static SingleEntity getSingleEntity(){
  
		//System.out.println(temp+"========"+Thread.currentThread() );
		try {
			temp = Thread.currentThread().getName() ;//测试用 
			Thread.sleep(5000);
			System.out.println( Thread.currentThread()+"======"+temp );//测试使用 
			
			if(singleEntity ==null){
				synchronized (lock) {  //同步锁为了保证对象的创建只有一个 
					if(singleEntity ==null ){
						System.out.println("33333======="+Thread.currentThread()+"=====创建单例对象");
						singleEntity = new SingleEntity();
					}
				}
			}

		} catch (InterruptedException e) {
			e.printStackTrace();
		}

		return singleEntity;
	}
	
}

 

 2 线程测试类

 

/**
 * @Title:TestThead
 * @Author Tony
 * @Date: 2014年6月20日 下午2:23:10
 * @Description: 线程类 
 */
public class TestThead extends Thread {

	public static void main(String[] args) {
		TestThead t1 = new TestThead();
		TestThead t2 = new TestThead();
		TestThead t3 = new TestThead();
		t1.start();
		t2.start();
		t3.start();
		TestThead t ;
		for(int i=0;i<50;i++ ){
			t = new TestThead();
			t.start();
		}
	}

	@Override
	public void run() {
		SingleEntity singleEntity1 = SingleEntity.getSingleEntity();
		//System.out.println( Thread.currentThread() +"   "+singleEntity1 );
	}
}