java的单实例模式

java的单实例模式

package com.t.utils;

public class TestSingleton {
	public static void main(String[] args) {
		ClassicSingleton s1 = ClassicSingleton.getInstance();
		ClassicSingleton s2 = ClassicSingleton.getInstance();
		System.out.println(s1 == s2);
	}
}


class ClassicSingleton {
	//创建一个私有的变量
	private static ClassicSingleton instance;
	//构造器私有，外部不能调用
	private ClassicSingleton() {
	}
	//加上synchronized，防止多线程
	public static synchronized ClassicSingleton getInstance() {
		if (instance == null) {
			instance = new ClassicSingleton();
		}
		return instance;
	}
}

输出结果为: true