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

Java can only inherit from one parent class. You cannot have multiple parents. However, you can have a class extend multiple interfaces.

Stay current with the latest in tech comm
Keep current with the latest trends in technical communication by subscribing to the I'd Rather Be Writing newsletter. 4,500+ subscribers