java 程序定义一个动物类(Animal)。属性(age、weight);方法(叫meow)、吃eat()、设置年龄setAge()，得到年龄getAge()等。然后再派生出两个子类狗(Dog)和奶牛(Cow)，再根据各自特性添加成员变量和成员方法。设计测试用例进行测试。

下面是实现动物类及其子类的Java代码：

// Animal.java
public class Animal {
    private int age;
    private double weight;

    public void setAge(int age) {
        this.age = age;
    }

    public int getAge() {
        return age;
    }

    public void setWeight(double weight) {
        this.weight = weight;
    }

    public double getWeight() {
        return weight;
    }

    public void eat() {
        System.out.println("Animal is eating.");
    }

    public void meow() {
        System.out.println("Animal is meowing.");
    }
}

// Dog.java
public class Dog extends Animal {
    private String breed;

    public void setBreed(String breed) {
        this.breed = breed;
    }

    public String getBreed() {
        return breed;
    }

    public void bark() {
        System.out.println("Dog is barking.");
    }
}

// Cow.java
public class Cow extends Animal {
    private boolean isMilkProducing;

    public void setIsMilkProducing(boolean isMilkProducing) {
        this.isMilkProducing = isMilkProducing;
    }

    public boolean getIsMilkProducing() {
        return isMilkProducing;
    }

    public void moo() {
        System.out.println("Cow is mooing.");
    }
}

下面是测试用例：

// Test.java
public class Test {
    public static void main(String[] args) {
        Animal animal = new Animal();
        animal.setAge(3);
        animal.setWeight(10.5);
        System.out.println("Animal age: " + animal.getAge());
        System.out.println("Animal weight: " + animal.getWeight());
        animal.eat();
        animal.meow();

        Dog dog = new Dog();
        dog.setAge(2);
        dog.setWeight(15.0);
        dog.setBreed("Golden Retriever");
        System.out.println("Dog age: " + dog.getAge());
        System.out.println("Dog weight: " + dog.getWeight());
        System.out.println("Dog breed: " + dog.getBreed());
        dog.eat();
        dog.meow();
        dog.bark();

        Cow cow = new Cow();
        cow.setAge(5);
        cow.setWeight(500.0);
        cow.setIsMilkProducing(true);
        System.out.println("Cow age: " + cow.getAge());
        System.out.println("Cow weight: " + cow.getWeight());
        System.out.println("Cow is milk producing: " + cow.getIsMilkProducing());
        cow.eat();
        cow.meow();
        cow.moo();
    }
}

运行结果如下：

Animal age: 3
Animal weight: 10.5
Animal is eating.
Animal is meowing.
Dog age: 2
Dog weight: 15.0
Dog breed: Golden Retriever
Animal is eating.
Animal is meowing.
Dog is barking.
Cow age: 5
Cow weight: 500.0
Cow is milk producing: true
Animal is eating.
Animal is meowing.
Cow is mooing.