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。

以下是 Java 代码实现：

public class Animal {
    private int age;
    private double weight;

    public Animal(int age, double weight) {
        this.age = age;
        this.weight = weight;
    }

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

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

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

    public int getAge() {
        return age;
    }
}

public class Dog extends Animal {
    private String breed;

    public Dog(int age, double weight, String breed) {
        super(age, weight);
        this.breed = breed;
    }

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

    public String getBreed() {
        return breed;
    }
}

public class Cow extends Animal {
    private int milkProduction;

    public Cow(int age, double weight, int milkProduction) {
        super(age, weight);
        this.milkProduction = milkProduction;
    }

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

    public int getMilkProduction() {
        return milkProduction;
    }
}

在这个例子中，Animal 类有两个属性 age 和 weight，以及三个方法 meow、eat 和 setAge/getAge。Dog 类和 Cow 类都继承了 Animal 类，并添加了自己的属性和方法。Dog 类添加了 breed 属性和 bark 方法，Cow 类添加了 milkProduction 属性和 moo 方法。这个例子展示了继承和多态的基本概念。