What is class in Java?

In Java, a class is a blueprint or template used to create objects.
It defines what data an object can store and what actions it can perform.

Java is an Object-Oriented Programming (OOP) language, and the concept of class is the foundation of Java programming.

Example

Think of a house plan.

• House plan -> Class
• Actual house built using the plan -> Object

The class does not represent a real object, but it describes how an object should look and behave.

Class Naming Rules in Java

While naming a class in Java, the following rules should be followed:

- Meaningful Name

The class name should be meaningful and clearly represent its purpose.
Example: Student, EmployeeDetails

- Starts with a Capital Letter

A class name should always start with a capital letter.
Example: StudentInfo, BankAccount

- No Spaces Allowed

Spaces are not allowed in class names.
Example:
Student Info - Not Correct
StudentInfo - Correct

- Numbers Allowed in Middle or End

Numbers can be used in the middle or at the end of a class name.
Example: Student1, Account2024

- Special Characters Not Allowed (Except _)

Special characters are not allowed in class names except underscore (_).
Example:
Student@Info - Not Correct
Student#Details - Not Correct
Student_Info - Correct

Example of a Valid Class Name

class StudentDetails1 {

}

What does a Java Class contain?

A Java class can contain:

• Variables (Fields) – to store data
• Methods – to define behavior
• Constructors – to initialize objects
• Access modifiers like public, private, etc.

Simple Java Class Example

class Student {
    String name;
    int age;

    void study() {
        System.out.println("Student is studying");
    }
}

Explanation:

• Student → Class name
• name, age → Variables
• study() → Method

Creating an Object from a Class

Student s1 = new Student();
s1.name = "Arun";
s1.age = 20;
s1.study();

Here:

• s1 is an object
• It is created using the Student class

Why are Classes Important in Java?

Classes help to:

• Organize code properly
• Reuse code efficiently
• Represent real-world entities
• Follow OOP principles like encapsulation, inheritance, and polymorphism
• Without classes, Java programs cannot be written.

Conclusion

A class in Java is a template, and an object is an instance of that class.
Classes make Java programs structured, reusable, and easy to understand.