Java入门——day45

1.人与学生

• 设计一个类people,有保护数据成员:age(年龄,整型)，name(姓名，string)，行为成员：两个构造函数（一个默认，另一个有参数）；void setValue(int m, string str)给age和name赋值；void display()输出age和name。

• 设计一个学生类student,公有继承类people,有私有成员：ID(学号,整型)，行为成员：两个构造函数（一个默认，另一个有参数）；void setID(int m)给ID赋值；void displayID()输出ID。

• 在main函数定义学生对象，给对象初始化赋值或调用setValue()和setID()赋值，并输出学生的信息。

//People类
public class People {
    protected int age;      //年龄
    protected String name;  //姓名
    public People() {
    }
    public People(int age, String name) {
        this.age = age;
        this.name = name;
    }
    public void setValue(int m,String str) {
        this.age=m;
        this.name=str;
    }
    public void display() {
        System.out.println("age:"+age);
        System.out.println("name:"+name);
    }
}

//Student类
public class Student extends People{
    private int ID;  //学号
    public Student() {
        super();
    }
    public Student(int age,String name,int ID) {
        super(age, name);
        this.ID=ID;
    }
    public void setID(int m) {
        this.ID=m;
    }
    public void displayID() {
        System.out.println("ID:"+ID);
    }
    public static void main(String[] args) {
        Student s=new Student(18,"李华",2020);
        s.display();
        s.displayID();
    }
}

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 2.多继承

 学生具有姓名，班级，学号等属性，有上课等行为；教师具有工号，工资等属性，有教课等行为；助教既是学生，又是老师，具有学生和老师的双重属性。请用类的多继承机制实现上述问题。

//学生类
public class Student {
    private String name;  //姓名
    private int room;     //班级
    private int ID;       //学号
    public Student() {
    }
    public Student(String name,int room,int ID) {
        this.name=name;
        this.room=room;
        this.ID=ID;
    }
    public void setValue(String name,int room,int ID) {
        this.name=name;
        this.room=room;
        this.ID=ID;
    }
    public void display1() {
        System.out.println("姓名："+name);
        System.out.println("班级："+room);
        System.out.println("学号："+ID);
        System.out.println("上课");
    }
}

//教师类
public class Teacher {
    private int num;  //工号
    private int pay;  //工资
    public Teacher() {
    }
    public Teacher(int num,int pay) {
        this.num=num;
        this.pay=pay;
    }
    public void setValue(int num,int pay) {
        this.num=num;
        this.pay=pay;
    }
    public void display2() {
        System.out.println("工号："+num);
        System.out.println("工资："+pay);
        System.out.println("教课");
    }
}

//助教类
public class Assistant {
    private class MyStudent extends Student{
    }
    private class MyTeacher extends Teacher{
    }
    private MyStudent s=new MyStudent();
    private MyTeacher t=new MyTeacher();
    public void output1() {
        s.setValue("Wang",1907,20194024);
        s.display1();
    }
    private void output2() {
        t.setValue(305,6000);
        t.display2();
    }
    public static void main(String[] args) {
        Assistant a=new Assistant();
        a.output1();
        a.output2();
    }
}

 注意：Java类与类之间只可以单继承，要想实现多继承可以有三种方法：多层继承、内部类和接口。