(1) Singleton mode

1. Concept

The so-called singleton pattern is to ensure that only one instance of the class exists in the entire application. Just like the application in the Java Web, it provides a global variable, which is quite useful, such as saving global data and implementing global operations.

 

2. Realization

The simplest implementation is to set the constructor of the class to private , so as to ensure that other classes cannot directly create new instances. Then provide a static instance in the class to return to the caller, so that there is only one instance.

package singleton pattern;

/**
 * Created by shyroke on 2018/4/23.
 */
public class SingleTon {

    private static final SingleTon newInstance = new SingleTon();

    private SingleTon(){}

    public SingleTon newInstance(){
        return  newInstance;
    }


    public static void main(String[] args) {
        SingleTon s1 = SingleTon.newInstance;
        SingleTon s2 = SingleTon.newInstance;
        System.out.println(s1);
        System.out.println(s2);
    }
}

The result is as shown below, the reference address is the same, indicating that it is the same object.