java 单例设计模式

package lianxi;

public class Singleton {//懒汉式单例设计模式
	private static Singleton st;
	
	private Singleton(){}
	
	public static Singleton getInstance(){
		if(st == null){
			st = new Singleton();
		}
		return st;
	}
	
	public static void main(String[] args){//验证
		Singleton s1 = Singleton.getInstance();
		Singleton s2 = Singleton.getInstance();
		
		System.out.println(s1 == s2);//运行结果 true
	}
}

 

 

package lianxi;

public class Singleton2 {//饿汉式单例设计模式
	private static Singleton2 st = new Singleton2();

	private Singleton2(){}

	public static Singleton2 getInstance(){
		return st;
	}

	public static void main(String[] args){//验证
		Singleton2 s1 = Singleton2.getInstance();
		Singleton2 s2 = Singleton2.getInstance();

		System.out.println(s1 == s2);//运行结果 true
	}
}