Android 单例设计模式之（双重校验锁）（同时具有效率与线程安全）

public class Singleton {
    private static volatile Singleton instance= null;
 
    private Singleton(){}
 
    public static Singleton getSingleton(){
        if(instance== null){
            synchronized (Singleton.class){
                if(instance== null){
                    instance= new Singleton();
                }
            }
        }
        return instance;
    }    
}