Java: Subclasses
Quick summary
- use
extends
keyword - subclasses inherits members of superclass
- unlike with interfaces, you’re not required to use all the fields and methods of the superclass
Eclipse example: subclasses
Detailed description
You can extend a class. When you do this, you basically create a subclass that inherits the parent classes’ members.
public class Apple extends Fruit
Now Apple can use all of Fruit’s members (fields and methods). However, unlike interfaces, when you extend a class, you are not required to use all of the fields and methods of the parent class.
… extends, lets us know the class’s parent class. A class’s parent (more properly, a super) class is the class from which the current class gets the bases of its definition. In particular, a class can use all public and protected methods in its parent class just as though they had been defined in the class at hand.
– Java 7 for Absolute Beginners
Inheritance defines relationships between the classes (and so between the objects) within an object-oriented system. All classes in Java have some other object as a parent. Java developers say that one object extends another. If you think about it for a minute, you shortly realize that there must be some object that starts it all. That special object (the only one that has no parent) is a class called Object. All other Java objects are descendants (sometimes through many levels) of Object.
– Java 7 for Absolute Beginners
Sponsored content
Java can only inherit from one parent class. You cannot have multiple parents. However, you can have a class extend multiple interfaces.