Java Inheritance Bob Dickerson March 2006 1 The idea of inheritanc e Inheritance is one of the essential features of object oriented programming and object oriented programming languages. InC++it is called derivation , in Eiffel it is called inheritance in Java it is called extension , all these words are quite good descriptions of the concept and they all mean the same. This introduction will start with the technicalities, how it works, and how to doit, not with how and why touse it, those questions will be discussed later ( …

Inheritance is a compile-time mechanism in Java that allows you to extend a class (called the base class or s uperclass ) with another class (called the derived class or subclass ). In Java, inheritance is used for two purposes: 1. class inheritance -create anew class as an extension of another class, primarily for the purpose of code reuse. That is, the derived class inherits the public methods and public data of the base class . Java only allows a class to have one immediate base class, i.e., single class inheritance. 2. interface inheritance - create a new class to implement the methods defined as part of an interface for the purpose of subtyping. That is a class that implements an interface “conforms to” (or is constrained by the type of) the interface. Java supports multiple interface inheritance. In Java, these two kinds of inheritance are made distinct by using different language syntax. For class inheritance, Java uses the keyword extends and for interface inheritance Java uses the keyword implements . public class derived-class-name extends base-class-name { // derived class methods extend and possibly override // those of the base class } public class class-name implements interface-name { // class provides an implementation for the methods // as specified by the interface }

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