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Java Programming Basics: Object Orientation

When learning Java, your understanding of basic concepts has to be sound. In particular, I have identified a set of five concepts that any Java professional must understand to be successful:

Object orientation
Runtime Polymorphism
Interfaces
IO Streams
Event Handling

In a series of articles titled Java Programming Basics, I take up each of these concepts individually to provide beginners (as well as experienced software engineers wanting to diversify their skill set) with a strong foundation of basic Java knowledge through compact explanations and practical examples. This first article in the series covers object orientation.

The Basics of Object Orientation

For a Java beginner, it is imperative to understand the concept of object orientation completely. The tenets of object orientation are encapsulation, polymorphism and inheritance. Encapsulation is binding the data of a class to the methods of the class, so that "private" data can be accessed only through "public" methods.

Polymorphism is a mechanism by which a generic operation can be implemented to work on different types of data. Polymorphism enables the programmer to define and use multiple implementations for the same method name, provided these implementations result in different signatures. For example, method overloading is compile-time (static) polymorphism.

Central to the understanding of polymorphism is the notion of method signatures (also known as mangled names). A method signature consists of the method name and types of its parameters. (Return type is not a part of the signature.) The following table breaks down the notion of method signature.

Sl No Method Prototype (specified by the developer) Method Signature (deduced by the compiler)

1. int max(int num1, int num2) max_int_int

2. int max(int num1, int num2, int num3) max_int_int_int

3. int max(int[] iArr, int n) max_int[]_int

The programmer specifies the prototypes and implementations. The compiler deduces the method signature from a method call and seeks an implementation that has the matching signature to resolve the call.

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