java继承

要求：

1.掌握继承的优点与实现

2.掌握子类重写父类的方法

3.掌握继承下构造方法的执行过程

4.掌握抽象类和抽象方法的使用

5.掌握final 修饰属性、方法和类

父类与子是 is_a  的关系

super 关键字访问父类成员：

1.super只能出现在子类方法和构造方法中

2.super调用构造方法时，只能是第一句

3.super 不能访问父类的private 成员

类不希望被继承  方法不希望被改写  属性值不希望被修改 ——final

优化电子宠物系统:

A:未使用super

Pet

package Animal2;

public class Pet {
    private String name;
    private int health;
    private int love;

    public void print() {

    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getHealth() {
        return health;
    }

    public void setHealth(int health) {
        this.health = health;
    }

    public int getLove() {
        return love;
    }

    public void setLove(int love) {
        this.love = love;
    }

}

Dog:

package Animal2;

public class Dog extends Pet {
    String strain;

    public void print() {
        System.out.println("宠物的自白");
        System.out.println("我的名字叫" + this.getName() + ",健康值是" + this.getHealth() + "和主人的亲密度是" + this.getLove()
                + ",我是一只酷酷的" + strain);
    }

    public String getStrain() {
        return strain;
    }

    public void setStrain(String strain) {
        this.strain = strain;
    }

}

Penguin:

package Animal2;

public class Penguin extends Pet {
    String sex;

    public void print() {
        System.out.println("宠物的自白");
        System.out.println(
                "我的名字叫" + this.getName() + ",健康值是" + this.getHealth() + "和主人的亲密度是" + this.getLove() + ",性别是" + sex);
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

}

B:使用super

 Pet

package Animal2;

public class Pet {
    private String name;
    private int health;
    private int love;

    public Pet() {
    }

    public Pet(String name, int health, int love) {
        this.name = name;
        this.health = health;
        this.love = love;
    }

    public void print() {

    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getHealth() {
        return health;
    }

    public void setHealth(int health) {
        this.health = health;
    }

    public int getLove() {
        return love;
    }

    public void setLove(int love) {
        this.love = love;
    }

}

Dog；

package Animal2;

public class Dog extends Pet {
    String strain;

    public Dog(String name, int health, int love, String strain) {
        super(name, health, love);
        this.strain = strain;
    }

    public Dog() {
        // TODO Auto-generated constructor stub
    }

    public void print() {
        System.out.println("宠物的自白");
        System.out.println("我的名字叫" + this.getName() + ",健康值是" + this.getHealth() + "和主人的亲密度是" + this.getLove()
                + ",我是一只酷酷的" + strain);
    }

    public String getStrain() {
        return strain;
    }

    public void setStrain(String strain) {
        this.strain = strain;
    }

}

Penguin；

package Animal2;

public class Dog extends Pet {
    String strain;

    public Dog(String name, int health, int love, String strain) {
        super(name, health, love);
        this.strain = strain;
    }

    public Dog() {
        // TODO Auto-generated constructor stub
    }

    public void print() {
        System.out.println("宠物的自白");
        System.out.println("我的名字叫" + this.getName() + ",健康值是" + this.getHealth() + "和主人的亲密度是" + this.getLove()
                + ",我是一只酷酷的" + strain);
    }

    public String getStrain() {
        return strain;
    }

    public void setStrain(String strain) {
        this.strain = strain;
    }

}

Text:

package Animal2;

import java.util.Scanner;

public class Text {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        System.out.println("欢迎来到宠物店!");
        System.out.println("请输入你要领养的宠物的名字:");
        String name;
        int num;
        name = input.next();
        System.out.println("Please choose the strain you like(1.狗狗 2.企鹅)");
        num = input.nextInt();
        if (num == 1) {
            System.out.println("请选择宠物的品种:(1.聪明的拉布多犬 2.酷酷的雪纳瑞)");
            Dog dog = new Dog();// 使用构造
            dog.setName(name);
            System.out.println(dog.getName());
            dog.print();
        } else {
            Penguin pen = new Penguin();
            pen.setName(name);
            System.out.println("选择企鹅的性别：1.Q仔 2.Q妹");
            num = input.nextInt();
            if (num == 1)
                pen.setSex("Q仔");
            else
                pen.setSex("Q妹");
            pen.print();
        }
    }
}

 由于单独定义Pet对象没有意义，所以抽象画Pet，抽象化方法，改变Pet

package Animal2;

public abstract class Pet {
    private String name;
    private int health;
    private int love;

    public Pet() {
    }

    public Pet(String name, int health, int love) {
        this.name = name;
        this.health = health;
        this.love = love;
    }

    public abstract void print();

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getHealth() {
        return health;
    }

    public void setHealth(int health) {
        this.health = health;
    }

    public int getLove() {
        return love;
    }

    public void setLove(int love) {
        this.love = love;
    }

}

实现汽车租赁计价功能：

1.客车轿车都属于车  Vehicle

2.车分轿车与客车