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COMPUTER SOFTWARE APPLICATION - CITS

LESSON 94 - 100: JAVA Classes, Overloading and

Inheritance

Java Classes/Objects

Classes and objects are the two main aspects of object-oriented programming.
Java is an object-oriented programming language.
Everything in Java is associated with classes and objects, along with its attributes and methods. For example:
in real life, a car is an object. The car has attributes, such as weight and color, and methods, such as drive and
brake.
A Class is like an object constructor, or a “blueprint” for creating objects
Create a Class

To create a class, use the keyword class:
Main.java
Create a class named “Main” with a variable x:
public class Main {
int x = 5;
}

Create an Object
In Java, an object is created from a class. We have already created the class named Main, so now we can use
this to create objects.

To create an object of Main, specify the class name, followed by the object name, and use the keyword new:
Example
Create an object called “myObj” and print the value of x:
public class Main {

int x = 5;
public static void main(String[] args) {
Main myObj = new Main();
System.out.println(myObj.x);
}

}
Java Methods
A method is a block of code which only runs when it is called.
You can pass data, known as parameters, into a method.
Methods are used to perform certain actions, and they are also known as functions.

Why use methods? To reuse code: define the code once, and use it many times.
Create a Method
A method must be declared within a class. It is defined with the name of the method, followed by parentheses
(). Java provides some pre-defined methods, such as System.out.println(), but you can also create your own
methods to perform certain actions:

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