Practice›Java Fundamentals›Module 7. Inheritance & Polymorphism›7.1 Inheritance

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7.1 Inheritance — adding to a subclass

Lesson

Inherited plus new

A subclass is not limited to what it inherits — it adds its own fields and methods too. And its new methods can use the inherited ones. So a subclass is: everything inherited from the superclass, plus whatever new members you give it.

Worked example

class Dog extends Animal {
    public Dog(String name) { super(name); }
    public String fetch() {
        return getName() + " fetches the ball";   // uses inherited getName()
    }
}

fetch() is Dog's own method, and inside it calls the inherited getName().

▶ Try it: run this — describe() is inherited and fetch() is Dog's own; both work on the same object.

class Animal {
    private String name;
    public Animal(String name) { this.name = name; }
    public String getName() { return name; }
    public String describe() { return name + " is an animal"; }
}
class Dog extends Animal {
    public Dog(String name) { super(name); }
    public String fetch() { return getName() + " fetches the ball"; }
}
public class Main {
    public static void main(String[] args) {
        Dog d = new Dog("Rex");
        System.out.println(d.describe());
        System.out.println(d.fetch());
    }
}

A subclass can...

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A subclass's own method can...

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Type exactly what this program prints.

class Animal { String n; Animal(String x){n=x;} String getName(){return n;} }
class Dog extends Animal { Dog(String x){super(x);} String fetch(){return getName()+" fetches";} }
public class Main { public static void main(String[] a){
    System.out.println(new Dog("Rex").fetch());
}}

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In Dog, fetch() calls getName(), which is...

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True or false?

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