目的：使用类来封装对象的属性和功能，子类完成设计。 题目1：创建一个类话题Tip类，该类有Id、话题内容两个属性，设计有参数和无参数构造方法，设计getInfo()方法打印话题内容。创建帖子类Topic继承帖子类，增加一个属性所属板块，设计构造方法注意使用super关键字，重写getInfo()方法打印内容为话题内容和所属板块信息。编写主类进行测试。 题目2：设计Drink类，有一个饮品名字和饮品价格两个属性，设计相应的get和set方法，设计一个奶茶类继承饮品类，增加成员变量成分Composition，设计getInfo()方法得到奶茶的相关信息；设计一个可乐类继承饮品类，增加成员变量品牌必brand，设计getInfo()方法得到可乐的相关信息；设计售卖类，售卖的内容是Drink类对象饮品，设计售卖方法，根据价格和数量计算需要付款多少钱，设计显示信息方法打印售卖的饮品是什么需要多少钱在屏幕上。设计主类进行上述类的测试。 题目3：创建一个Vehicle类并将它声明为抽象类。在Vehicle类中声明两个抽象方法run和speed。创建两个类Car 和 Motorbike 从Vehicle类继承，并在这两个类中实现抽象类方法。重写的方法自己定义方法的操作。设计主类，在该类中创建Car和 Motorbike的实例，进行上述重写方法的测试。

题目1的代码实现如下：

public class Tip {
    private int id;
    private String content;

    public Tip() {}

    public Tip(int id, String content) {
        this.id = id;
        this.content = content;
    }

    public void setId(int id) {
        this.id = id;
    }

    public int getId() {
        return id;
    }

    public void setContent(String content) {
        this.content = content;
    }

    public String getContent() {
        return content;
    }

    public void getInfo() {
        System.out.println("话题内容：" + content);
    }
}

public class Topic extends Tip {
    private String category;

    public Topic() {}

    public Topic(int id, String content, String category) {
        super(id, content);
        this.category = category;
    }

    public void setCategory(String category) {
        this.category = category;
    }

    public String getCategory() {
        return category;
    }

    @Override
    public void getInfo() {
        System.out.println("话题内容：" + getContent() + "，所属板块：" + category);
    }
}

public class Main {
    public static void main(String[] args) {
        Tip tip = new Tip(1, "如何学好Java");
        tip.getInfo();

        Topic topic = new Topic(2, "Java基础知识", "编程语言");
        topic.getInfo();
    }
}

题目2的代码实现如下：

public class Drink {
    private String name;
    private double price;

    public Drink() {}

    public Drink(String name, double price) {
        this.name = name;
        this.price = price;
    }

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

    public String getName() {
        return name;
    }

    public void setPrice(double price) {
        this.price = price;
    }

    public double getPrice() {
        return price;
    }
}

public class MilkTea extends Drink {
    private String composition;

    public MilkTea() {}

    public MilkTea(String name, double price, String composition) {
        super(name, price);
        this.composition = composition;
    }

    public void setComposition(String composition) {
        this.composition = composition;
    }

    public String getComposition() {
        return composition;
    }

    public void getInfo() {
        System.out.println("饮品名字：" + getName() + "，饮品价格：" + getPrice() + "，成分：" + composition);
    }
}

public class Cola extends Drink {
    private String brand;

    public Cola() {}

    public Cola(String name, double price, String brand) {
        super(name, price);
        this.brand = brand;
    }

    public void setBrand(String brand) {
        this.brand = brand;
    }

    public String getBrand() {
        return brand;
    }

    public void getInfo() {
        System.out.println("饮品名字：" + getName() + "，饮品价格：" + getPrice() + "，品牌：" + brand);
    }
}

public class Sales {
    public void sell(Drink drink, int count) {
        double total = drink.getPrice() * count;
        System.out.println("售卖的饮品是：" + drink.getName() + "，需要付款：" + total + "元");
    }
}

public class Main {
    public static void main(String[] args) {
        MilkTea milkTea = new MilkTea("珍珠奶茶", 15.0, "珍珠、牛奶、茶叶");
        milkTea.getInfo();

        Cola cola = new Cola("可乐", 3.0, "可口可乐");
        cola.getInfo();

        Sales sales = new Sales();
        sales.sell(milkTea, 2);
        sales.sell(cola, 3);
    }
}

题目3的代码实现如下：

public abstract class Vehicle {
    public abstract void run();

    public abstract void speed();
}

public class Car extends Vehicle {
    @Override
    public void run() {
        System.out.println("车在跑");
    }

    @Override
    public void speed() {
        System.out.println("车速度很快");
    }
}

public class Motorbike extends Vehicle {
    @Override
    public void run() {
        System.out.println("摩托车在跑");
    }

    @Override
    public void speed() {
        System.out.println("摩托车速度很快");
    }
}

public class Main {
    public static void main(String[] args) {
        Vehicle car = new Car();
        car.run();
        car.speed();

        Vehicle motorbike = new Motorbike();
        motorbike.run();
        motorbike.speed();
    }
}