Java日志第12天 2020.7.17

第五章 类的继承和多态

5.6综合实例

一般试卷中都有选择题，选择题又可分为单选择题和多选择题。其简单的流程图如图5-4所示。

 

 父类Question定义：

 

 子类SingleQuestion

 

 子类MultiQuestion

 

 测试类PaperDemo

 

 

5.8 上机练习

1.请分别定义父类People和子类Student，观察Student是如何共享父类属性和方法的。

public class People {
    public String name;
    public String sex;
    public int age;
    public String getName(){
        return name;
    }
    public void setName(String name){
        this.name=name;
    }
    public String getSex(){
        return sex;
    }
    public void setSex(String sex){
        this.sex=sex;
    }
    public int getAge(){
        return age;
    }
    public void setAge(int age){
        this.age=age;
    }
}

public class Student extends People {
    private String deparetment;//系别
    private String specialty;//专业
    String name = super.name;
    public void test(){
        super.getAge();
    }
}

2.在题1的People中定义final方法，然后在类Student中定义与该final相同的方法，观察Student的变化。

public class People {
    public String name;
    public String sex;
    public int age;
    public String getName(){
        return name;
    }
    public void setName(String name){
        this.name=name;
    }
    public String getSex(){
        return sex;
    }
    public void setSex(String sex){
        this.sex=sex;
    }
    public int getAge(){
        return age;
    }
    public void setAge(int age){
        this.age=age;
    }
    public final void test1(){
    }
    private final void test2(){
    }
}

public class Student extends People {
    private String deparetment;//系别
    private String specialty;//专业
    String name = super.name;
    public void test(){
        super.getAge();
    }
    public void test1(){//父类权限为public，且被final修饰报错！
    }
    public void test2(){//父类权限为private，且被final修饰 不报错！
    }
}

3.将题目1的父类People定义成抽象类，用子类Student来继承它。

public abstract class People {
    public String name;
    public String sex;
    public int age;
    public String getName(){
        return name;
    }
    public void setName(String name){
        this.name=name;
    }
    public String getSex(){
        return sex;
    }
    public void setSex(String sex){
        this.sex=sex;
    }
    public int getAge(){
        return age;
    }
    public void setAge(int age){
        this.age=age;
    }
    public abstract void setValues(String name,String sex,int age);
}

public class Student extends People {
    private String deparetment;//系别
    private String specialty;//专业
    String name = super.name;
    public void test(){
        super.getAge();
    }
    public void setValues(String name,String sex,int age){
        super.name=name;
        this.sex=sex;
        this.age=age;
    }

    public static void main(String[] args) {
        People people = new Student();
        people.setValues("伍正云","男",25);
        System.out.print(people.getName()+"\t"+people.getSex()+"\t"+people.getAge());
        System.out.println();
    }
}

 

 

 

今天把第五章学完了，感觉前边学的有点不扎实，明天开始第六章的同时，要往回看一看。