单例模式

单例模式实现

方法一：双重校验锁
public class Singleton{
    private volatile static Singleton instance=null;
    private Singleton{

    }
    public static Singleton getInstance(){
        if(null==instance){
            synchronized(Singleton.class){
                if(null==instance){
                    instance=new Singleton();
                }
            }
        }
        return instance;
    }
}
方法二：静态内部类
public class Singleton{
    private Singleton{

    }
    public static class Inner{
        private static Singleton instance=new Singleton();
    }
    public static Singleton getInstance(){
        return Inner.instance;
    }
}