饿汉式单例
public class Singleton{
private Singleton(){}
private static Singleton instance =new Singleton();
public static Singleton getInstance(){
return instance;
}
}
懒汉式单例
public class Singleton{
private statis Singleton instance =null;
private Singleton (){}
public static synchronized Singleton getInstance(){
if (instance == null ) instance = new Singleton();
return instance;
}
}
实现单例需要注意以下事项:
1、将构造器私有,不允许外接通过构造器创建对象;
2、通过公开的静态方法向外界返回类的唯一实例