Classes are the fundamental building blocks of a Java program. You can define an Employee class as follows:
class Employee {
  int age;

  double salary;
}

1. By convention, class names capitalize the initial of each word.
2. For example: Employee, Boss, DateUtility, PostOffice, RegularRateCalculator.
3. This type of naming convention is known as Pascal naming convention.
4. The other convention, the camel naming convention, capitalize the initial of each word, except the first word.
5. Method and field names use the camel naming convention.

A Simple Class Definition

class Count {

    public static void main(String args[])

        throws java.io.IOException

    {

        int count = 0;

        while (System.in.read() != -1)

            count++;

        System.out.println("Input has " + count + " chars.");

    }

}

In the Java language, all methods and variables must exist within a class. So, the first line of the character-counting application defines a class, Count, that defines the methods, variables, and any other classes needed to implement the character-counting application. Since this program is such a simple one, the Count class just defines one method named main().