use class in a class java code example

Example 1: classes in java

// this might help you understand how classes work
public class MathTest {

    public static void main(String[] args) {

        class MathAdd {

            int num1;
            int num2;

            public int addNumbers() {

                int addThemUp = num1 + num2;
                return addThemUp;
            }
        }

        MathAdd addition = new MathAdd(); // create a new instance of the class

        // you can access variables from the class 
        addition.num1 = 10; 
        addition.num2 = 20;

        // and use the method from the class to add them up
        System.out.println(addition.addNumbers());

    }
}

Example 2: class in java

Class is a blueprint or template which
you can create as many objects as you 
like. Object is a member or instance
of a class.
Class is declared using class keyword,
Object is created through
new keyword mainly. A class is a template
  for objects. A class defines 
object properties including a valid range
    of values, and a default value. 
A class also describes object behavior.