2024/10/8

Main.java

package org.example;

public class Main {
    public static void main(String[] args) {
        StudentID stu1,stu2;
        stu1=StudentID.getStudentID();
        stu2=StudentID.getStudentID();
        String str1,str2;
        str1=stu1.getID();
        str2=stu2.getID();
        System.out.println("第一次学号："+str1);
        System.out.println("第二次学号："+str2);
    }
}

StudentID.java

package org.example;

public class StudentID {
    private static StudentID instance=null;
    private String ID;

    public String getID() {
        return ID;
    }

    public void setID(String iD) {
        ID = iD;
    }

    private StudentID()
    {

    }

    public static StudentID getStudentID()
    {
        if(instance==null) {
            instance=new StudentID();
            instance.setID("20223683");
        }
        else
        {
            System.out.println("一个学生只能有一个学号");
        }
        return instance;
    }
}