JAVA语言程序设计课后习题----第七单元解析（仅供参考）

1　　本题水题，就是想让你理解继承的含义

public class Animaal {
    public double weight;
    public void eat(){
    }
}

public class Bird extends Animaal {
    public int numberOfFins;
    public void fly(){}


}

public class Dog extends Animaal {
    public int numberOflegs;
    public void walk(){}


}

public class Fish extends Animaal{
    public int numberOfFins;
    public void swim(){}


}

 2　　本题主要考类的继承和方法的重写，方法的重写关键字@Override

 

public class Circle {
    public int radius;
    public double getArea(){
        return Math.PI*radius*radius;
    }
}

public class Cylinder extends Circle {
    public double height;

    public Cylinder() {
    }

    public Cylinder(double height) {
        this.height = height;
    }
    public Cylinder(int radius,double height){
        this.radius=radius;
        this.height=height;
    }
    //    体积
    public double getVolume(){
        return Math.PI*radius*radius*height;
    }
    //    覆盖Circle 里面的getArea函数求圆柱的体积
    @Override
    public double getArea(){
        return Math.PI*radius*radius*2+2*Math.PI*radius*height;
    }
}

import java.util.Scanner;

public class ch08 {
    public static void main(String[] args) {

        Scanner input = new Scanner(System.in);
        System.out.println("请输入圆柱的半径、高");
        Cylinder cylinder = new Cylinder(input.nextInt(),input.nextDouble());
        System.out.println("圆柱的体积为:"+cylinder.getVolume());
        System.out.println("圆柱的面积为:"+cylinder.getArea());
    }
}

 3　　本题水题，考的方法和上面两题类似，注意题目要求即可

public class Auto {
    public double speed;
    //    启动的方法
    public void start(){
        System.out.println("插上钥匙、系上安全带、一脚把离合踩到底、挂上一档、打左转向、缓慢抬脚、汽车平稳启动");
    }
    //    加速的方法
    public void speedUp(){
        System.out.println("脚慢踩油门、松开油门、踩离合到底、换挡、加速完成");
    }
    //    停止的方法
    public void stop(){
        System.out.println("慢踩刹车、达到额定速度、松开刹车、踩离合、换挡、持续到速度为0");
    }
}

public class Bus extends Auto {
    public int passenger;
    public Bus(int passenger){this.passenger=passenger;}
    //    上车
    public int gotOn(){ return ++passenger;
    }
    //    下车
    public int gotOff(){return --passenger;}
}

import java.util.Scanner;

public class ch09 {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        System.out.println("请输入开始车上的人数");
        Bus bus = new Bus(input.nextInt());
        System.out.println("旅客上车");
        System.out.println(bus.gotOn());
        bus.start();
        bus.speedUp();
        System.out.println("旅客上下车");
        System.out.println(bus.gotOff());
        bus.stop();
    }
}

 

4　　本题主要考继承和抽象方法，关键字@Override

 

　

public class Shape {
    public int radius;
    public int l;
    public double getPrimeter(){
        return 0;
    }
    public double getArea(){return 0;}
}

public class Square extends Shape {
    public Square() {
    }

    public Square(int radius){this.radius=radius;}
    @Override
    public double getPrimeter(){
        return 4*radius;
    }
    @Override
    public double getArea(){
        return radius*radius;
    }

}

public class ch10 {
    public static void main(String[] args) {
        Square square = new Square(10);
        System.out.println("正方形的周长为:"+square.getPrimeter());
        System.out.println("正方形的面积为:"+square.getArea());
    }
}

5　　本题主要考方法的覆盖，构造方法的重写

public class Rectangle {
    public double length,width;

    public Rectangle(double length, double width) {
        this.length=length;
        this.width=width;
    }
}

public class Cuboid extends Rectangle{
    public double height;

    public Cuboid(double length, double width, double height) {
        super(length, width);
        this.height = height;
    }

    public double volume(){
        return length*width*height;
    }
}

public class ch11 {
    public static void main(String[] args) {
        System.out.println("长方体的长、宽、高分别为10、5、2!");
        Cuboid cuboid = new Cuboid(10,5,2);
        System.out.println("长方体的体积为:"+cuboid.volume());
    }
}