2024.12.3

 

public class Student {

    private static Student instance=null;

    private String ID;

    private Student(){}

    private void setID(String id)

    {

        ID=id;

    }

    public static Student getInstance()

    {

        if(instance==null)

        {

            instance=new Student();

            instance.setID("20223674");

            System.out.println("注册完成");

        }

        else {

            System.out.println("该学生的学号已经存在");

        }

        return instance;

    }

    public String getID(){

        return ID;

    }

}

 

public class Main {

    public static void main(String[] args) {

        Student s1,s2;

        System.out.println("第一次");

        s1=Student.getInstance();

        System.out.println("第二次");

        s2=Student.getInstance();

 

        System.out.println("两次的学号是否一致"+s1.getID().equals(s2.getID())+"。s1的学号为"+s1.getID()+"，s2的学号为"+s2.getID());

        System.out.println("两次获取的对象是否一致"+(s1==s2));

    }

}