Java - 继承

Java未写继承的类, 默认继承标准基类Object.
每个类都可以包含一个main()静态方法, 用于单元测试.
继承是对类的复用, 函数内使用super调用基类的相同方法, 区分递归.
派生类中可以添加新的方法, 对基类进行扩展.

代码:

/**
 * 继承
 * <p/>
 * Created by wang on 15/8/7.
 */

class Cleaner {
    private String s = "Cleaner";

    public static void main(String[] args) {
        Cleaner x = new Cleaner();
        x.dilute().apply().scrub();
        System.out.println(x);
    }

    public void append(String a) {
        s += a;
    }

    public Cleaner dilute() {
        append(" dilute");
        return this;
    }

    public Cleaner apply() {
        append(" apply");
        return this;
    }

    public Cleaner scrub() {
        append(" scrub");
        return this;
    }

    @Override
    public String toString() {
        return s;
    }
}

class Detergent extends Cleaner {
    public static void main(String[] args) {
        Detergent d = new Detergent();
        ((Detergent) d.dilute().apply()).scrub().foam();
        System.out.println(d);
    }

    @Override
    public Detergent scrub() {
        append(" Detergent: scrub()");
        super.scrub();
        return this;
    }

    public Detergent foam() {
        append(" foam");
        return this;
    }
}

public class Disinfectant extends Detergent {
    public static void main(String[] args) {
        Disinfectant d = new Disinfectant();
        ((Disinfectant) d.dilute().apply()).scrub().sterilize();
        System.out.println(d);
        Detergent.main(args);
        Cleaner.main(args);
    }

    @Override
    public Disinfectant scrub() {
        append(" Disinfectant: scrub()");
        super.scrub();
        return this;
    }

    public Disinfectant sterilize() {
        append(" sterilize");
        return this;
    }
}
/**
 * Output:
 Cleaner dilute apply Disinfectant: scrub() Detergent: scrub() scrub sterilize
 Cleaner dilute apply Detergent: scrub() scrub foam
 Cleaner dilute apply scrub
 */