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Football2.java

/** * 懒汉式单例 * 用的时候再创建一个对象，线程不安全 * @author Administrator * */class FootBall2 {        private static int count;        private static FootBall2 fb;	private FootBall2(){            System.out.println("初始化" + (count++) + "次");        }		public  static FootBall2 getFootBall(){		if(fb == null){			synchronized (FootBall2.class) {				if(fb == null){										fb = new FootBall2();								}			}		}		return fb;	}}

测试类SinglerTest2.j：

public class SinglerTest2 {	public static void main(String[] args) {		for (int i = 0; i < 100; i++) {			new Thread(new Runnable() {				@Override				public void run() {					System.out.println(Thread.currentThread().getName() + ":" + FootBall2.getFootBall());				}			}).start();		}	}}

结果：

初始化0次

...

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