java 设计模式之单例模式

public class Singleton2 {
	
	//私有的构造方法
	private Singleton2() {
		
	}
	
	//对外提供静态方法
	//增加synchronized，保证线程安全性
	public synchronized static Singleton2 getInstance() {
		if (instance == null) {
			instance = new Singleton2();
		}
		return instance;
	}
	
	//静态实例
	private static Singleton2 instance = new Singleton2();
}