设计模式--创建者--单例

单例模式的时机是当实例存在多个会引起程序逻辑错误的时候。比如类似有序的号码生成器这样的东西,电话号码集

public class Singleton {
	private static Singleton instance = null;

	private Singleton() {
	}

	public static  Singleton getInstance() {
		if (instance == null) {
			instance = new Singleton();
		}
		return instance;
	}
	
	public static void main(String[] args) {
		System.out.println(Singleton.getInstance());
		System.out.println(Singleton.getInstance());
	}
}

输出结果：
com.danlipattern.Singleton@de6ced
com.danlipattern.Singleton@de6ced