1903021111—郭付琴—Java第十一周作业—继承、多态和抽象类的应用
项目 | 内容 |
课程班级博客链接 | 19级信计班 |
这个作业要求链接 | 第十一周作业 |
博客名称 | 1903021111—郭付琴—Java第十一周作业—继承、多态和抽象类的应用 |
要求 | 每道题要有题目,代码(使用插入代码,不会插入代码的自己查资料解决,不要直接截图代码!!),截图(只截运行结果) |
题目1:
-
类Person定义了姓名name,出生年份birthYear,其子类Graduate在继承父类的基础上新增定义了成绩gpa、毕业年份graduateYear。编写测试类,输出毕业生的姓名、年龄、毕业年份、成绩。
- 提示:父类要有构造方法,子类通过super调用父类构造方法。
代码:
- 父类:
package xjweek11;
public class Person {
String name;
int birthYear;
public Person(String name, int birthYear) {
super();
this.name = name;
this.birthYear = birthYear;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getBirthYear() {
return birthYear;
}
public void setBirthYear(int birthYear) {
this.birthYear = birthYear;
}
}
- 子类:
package xjweek11;
public class Graduate extends Person {
int gap;
int graduateYear;
public Graduate(String name, int birthYear, int gap, int graduateYear) {
super(name, birthYear);
this.gap = gap;
this.graduateYear = graduateYear;
}
public int getGap() {
return gap;
}
public void setGap(int gap) {
this.gap = gap;
}
public int getGraduateYear() {
return graduateYear;
}
public void setGraduateYear(int graduateYear) {
this.graduateYear = graduateYear;
}
}
- 测试类:
package xjweek11;
public class GraduateTest {
public static <Greduate> void main(String[] args) {
Graduate G = new Graduate("唐三",1991,100,2014);
System.out.println("姓名:"+G.getName()+"\n年龄:"+(G.getGraduateYear()-G.getBirthYear())+"\n毕业年份:"+G.getGraduateYear()+"\n成绩:"+G.getGap());
}
}
运行结果:
题目2:
- 定义一个基本类Shape,有一个draw方法,定义三个类Circle(圆)、Triangle(三角形)、Square(正方形)都继承于Shape。在测试类中定义一个方法doStuff,传入基本类shape为参数,并调用draw方法。使用父类Shape创建三个类Circle、 Triangle、Square的实例对象并分别作为参数传入draw方法中。
- 提示:多态
代码:
- 父类:
package xjweek11;
public class Shape {
void draw(){
}
}
- 子类:
package xjweek11;
public class Circle extends Shape {
void draw(){
System.out.println("Circle.draw()");
}
}
package xjweek11;
public class Triangle extends Shape {
void draw(){
System.out.println("Triangle.draw()");
}
}
package xjweek11;
public class Square extends Shape {
void draw(){
System.out.println("Square.draw()");
}
}
- 测试类:
package xjweek11;
public class ShapeTest {
static void doStuff(Shape s){
s.draw();
}
public static void main(String[] args) {
Shape c=new Circle();
Shape s=new Square();
Shape t=new Triangle();
doStuff(c);
doStuff(s);
doStuff(t);
}
}
运行结果:
题目3:
-
所有的动物都有一个父类Animal,再定义两个子类Bird(鸟)和Dog(狗)继承自Animal,并实现父类中的bark(叫唤)方法。
- 提示:抽象
代码:
- 父类:
package xjweek11;
public class Animal {
void bark() {
}
}
- 子类:
package xjweek11;
public class Bird extends Animal {
void bark(){
System.out.println("鸟的叫声是:叽叽喳喳");
}
}
package xjweek11;
public class Dog extends Animal {
void bark(){
System.out.println("狗的叫声是:汪汪汪");
}
}
- 测试类:
package xjweek11;
public class AnimalTest {
public static void main(String[] args) {
Bird b=new Bird();
Dog d=new Dog();
b.bark();
d.bark();
}
}
运行结果:
题目4:
-
不同几何图形的面积计算公式是不一样的,可是,它们具有的特性是一样的,都具有长和宽这两个属性,也都具有面积计算的方法。根据抽象的概念计算长方形的面积和三角形的面积。
- 提示:抽象
代码:
- 父类:
package xjweek11;
public abstract class Shape {
abstract void Area();
}
- 子类:
package xjweek11;
public class Rectangle extends Shape {
int lenght;
int height;
public Rectangle(int lenght, int height) {
super();
this.lenght = lenght;
this.height = height;
}
void Area() {
System.out.println("长方形的面积是:"+lenght*height);
}
}
package xjweek11;
public class Triangle extends Shape {
int lenght;
int height;
public Triangle(int lenght, int height) {
super();
this.lenght = lenght;
this.height = height;
}
void Area() {
System.out.println("三角形的面积是:"+lenght*height/2);
}
}
- 测试类:
package xjweek11;
public class ShapeTest {
public static void main(String[] args) {
Rectangle R = new Rectangle(1,9);
R.Area();
Triangle T = new Triangle(9,1);
T.Area();
}
}
运行结果:
- 扩展阅读:Java中的继承和多态、Java中的抽象类
- 心得:1、在已经存在的类的基础上进行扩充和改造,形成一个新的类。满足“is a”的关系就是继承。
2、多态是一种事务,多种形态。用名字一样的代码根据要求的不同,干不一样的事情。分类:对象的多态。(父对象引用指向子类实例)方法的多态。(分为方法的重载和重写或者覆盖)
3、类:用来描述具有共同性质的一组事物的自定义复合数据类型。