图解设计模式（五）单例模式

package com.design;

public class Singleton {
	private static Singleton singleton;
	private Singleton() {
		System.out.println("生成了一个实例");
	}
	public static Singleton getInstance() {
		if (singleton == null) {
			synchronized (Singleton.class) {
				if (singleton == null) {
					singleton = new Singleton();
				}
			}
		}
		return singleton;
	}
	
	public static void main(String[] args) {
		Singleton.getInstance();
		Singleton.getInstance();
	}
}