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objectS

5

Learning Objectives

5.1 Introduction to Objects 5.2 Class
5.3 Basic Concept of a Virtual Machine 5.4 Basic Input/Output Using Scanner Class from JDK
5.5 Errors 5.6 Basic Concept of an Exception

In the previous chapter, we have read about object-oriented programming and its basic principles. Object-oriented
programming has two basic components. They are known as “objects” and “classes”. In this chapter, we will deal with
these components in detail.

5.1 INTRODUCTION TO OBJECTS

Is there anything in the world that is not an object or not associated with an object? The answer is “NO”. Anything
we can imagine in the world is an object. Every object has an entity that has a state, behaviour and events. The
properties which are associated with an object at any given time contain data. This is called a state. The functionality
that an object is supposed to perform is called “behaviour”. Whenever the value of the object changes, it raises
events.

Suppose, we consider a fan as a real-world object.
The properties/characteristics of the object can be:

1. Number of blades (2/3/4)
2. The manufacturing company
3. The speed of the fan

The behaviour of the object can be:
1. Switched on/off
2. The speed of the fan should be passed as data by revolving the regulator.
The event can be:
When the fan revolves, it delivers air. This can be expressed as an event.

Thus, an object is a unique entity that contains properties, methods and events in an object-oriented programming
language.
Let us take another real-life object, a well-known vegetable “radish”.

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