单例模式

package com.demo.singleton;

public class Singleton {
	
	private static Singleton uniqueInstance;
	String str;
	private Singleton(){//构造器私有
		str=Math.random()*10000+"";
	}
	public static synchronized Singleton getInstance(){
		if(uniqueInstance==null){
			uniqueInstance=new Singleton();
		}
		return uniqueInstance;
	}
	public void getRandomStr(){
		System.out.println(str);
	}
}

package com.demo.singleton;

public class Application {

	public static void main(String[] args) throws InterruptedException {

		Singleton s1=Singleton.getInstance();
		Singleton s2=Singleton.getInstance();
		s1.getRandomStr();
		s2.getRandomStr();
		System.out.println(s1==s2);
		//Singleton s3=new Singleton();//出错
	}
}