Course material –Lecture Notes
Introduction to java
Java is an Object-Oriented Language. As a language that has the Object Oriented feature, Java
supports the following fundamental concepts:
In this chapter, we will look into the concepts Classes and Objects.
Object - Objects have states and behaviors. Example: A dog has states - color, name,
breed as well as behaviors -wagging, barking, eating. An object is an instance of a class.
Class - A class can be defined as a template/blue print that describes the behaviors/states
that object of its type support.
Objects in Java:
Let us now look deep into what are objects. If we consider the real-world we can find many
objects around us, Cars, Dogs, Humans, etc. All these objects have a state and behavior.
If we consider a dog, then its state is - name, breed, color, and the behavior is - barking,
If you compare the software object with a real world object, they have very similar
Software objects also have a state and behavior. A software object's state is stored in fields and
behavior is shown via methods.
So in software development, methods operate on the internal state of an object and the object-toobject communication is done via methods.
Classes in Java:
A class is a blue print from which individual objects are created.
A sample of a class is given below:
CS6501 Internet Programming – Unit - I