单例设计模式

 懒汉式

 

public class Singleton {

    private static Singleton sing;

    private Singleton(){}

    public static Singleton newInstance(){
        if(sing==null){
            sing = new Singleton();
        }
        return sing;
    }

}

 

饿汉式

 

public class Singleton {

    private static Singleton sing = new Singleton();

    private Singleton(){}

    public static Singleton newInstance(){
        return sing;
    }

}