JAVA中不会的知识

Question

给定如图 7 - 2 所示的
Animal类及其子类Bird和
Fish的继承关系UML图。
(1)编写代码实现这些类，为这些类定义无参构造方法，在构
造方法中输出一句话。实现每个类中定义的方法。
(2)编写测试类AnimalTest，在main()方法中创建一个Bird对
象，访问该对象的numberOfWings成员和eat()与fly()方法。
(3)编写测试类AnimalTest2，在main()方法中创建一个Fish
对象，访问该对象的numberOfFins成员和eat()与swim()方法。
public class Animal {
private double weight;
//Animal类的无参构造方法Animal()
补充代码
public void eat(){
System.out.println("调用了Animal类的eat方法");
}

public class Fish extends Animal{
public int numberOfFins;
//Fish无参构造方法Fish()
补充代码
public void eat(){
System.out.println("调用了Fish类的eat方法");
}
public void swim(){
System.out.println("有"+numberOfFins+"条鱼河里游");
}
}
public class Bird extends Animal {
public int numberOfWings;
//Bird类的无参构造函数Bird()
补充代码
public Bird(int numberOfWings){
this.numberOfWings=numberOfWings;
System.out.println("调用了Bird类的有参构造函数");
}
public void fly(){
System.out.println("共有"+numberOfWings+"只飞起来了"); } }

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

Answer 1

public class Animal {
    private double weight;
    
    public Animal() {
        System.out.println("调用Animal类的无参构造函数");
    }

    public void eat() {
        System.out.println("调用了Animal类的eat方法");
    }
}

class Fish extends Animal {
    public int numberOfFins;
    
    public Fish() {
        System.out.println("调用了Fish类的无参构造函数");
    }

    public Fish(int numberOfFins) {
        this.numberOfFins = numberOfFins;
        System.out.println("调用了Fish类的有参构造函数");
    }

    @Override
    public void eat() {
        System.out.println("调用了Fish类的eat方法");
    }

    public void swim() {
        System.out.println("有" + numberOfFins + "条鱼河里游");
    }

    public int getNumberOfFins() {
        return numberOfFins;
    }

    public void setNumberOfFins(int numberOfFins) {
        this.numberOfFins = numberOfFins;
    }
}

class Bird extends Animal {
    public int numberOfWings;
    
    public Bird() {
        System.out.println("调用了Bird类的无参构造函数");
    }

    public Bird(int numberOfWings) {
        this.numberOfWings = numberOfWings;
        System.out.println("调用了Bird类的有参构造函数");
    }

    @Override
    public void eat() {
        System.out.println("调用了Bird类的eat方法");
    }

    public void fly() {
        System.out.println("共有" + numberOfWings + "只飞起来了");
    }

    public int getNumberOfWings() {
        return numberOfWings;
    }

    public void setNumberOfWings(int numberOfWings) {
        this.numberOfWings = numberOfWings;
    }
}

class AnimalTest {
    public static void main(String[] args) {
        Fish fish = new Fish(3);
        int numberOfFins = fish.getNumberOfFins();
        fish.eat();
        System.out.println("numberOfFins: " + numberOfFins);
        fish.swim();

        System.out.println();

        Bird bird = new Bird(5);
        int numberOfWings = bird.getNumberOfWings();
        bird.eat();
        System.out.println("numberOfWings: " + numberOfWings);
        bird.fly();
    }
}

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