Java Classes

What is a Class in Java?

A Java Class is a group of objects, which have common properties. It is a template/blueprint from which objects are created. It is a Logical entity. It can’t be Physical.

A Class in Java programming language can contain:

1. Fields or Variables
2. Java Methods
3. Java Constructors
4. Java Blocks
5. Nested Class and Interface

Syntax

class <class_name>{

//write code here
}

Java Class Example

class Add{
public void addtwono(){
int num1 = 20;
int num2 = 30;

System.out.println ("First number: "+num1);
System.out.println ("Second number: "+num2);

//calculate sum
int sum = num1 + num2;

//print sum
System.out.println ("Addition of "+num1+" and "+num2+" is = "+sum);
}
}

public class ClassDemo1{
public static void main (String[] args){

//creating new object
Add obj = new Add();

//call method
obj.addtwono();
}
}

Save this file as 'ClassDemo1.java'
Compile: $javac ClassDemo1.java
Execute: $java ClassDemo1
Output:

First number: 20
Second number: 30
Addition of 20 and 30 is = 50