Java Swing Calculator Tutorial

1. A four-function calculator with the following functions:
* Addition - adds two numbers: n1 + n2.
* Subtraction - subtracts number two from number one: n1 - n2.
* Multiplication - Multiplies two numbers: n1 * n2.
* Division - divides number two into number one: n1 / n2.

2. Used JButton for the numbers and functions.

3. Used Jmenu for File and help.

4. Created a class to respond to the events caused by numbers, functions, exit, help and about functionality.

5. Used BorderLayout to layout various components in the Calculator Frame. A BorderLayout lays out a container, arranging and resizing its components to fit in five regions: north, south, east, west, and center.