Major features

• GUI development
• Excellent layout management
• Complicated logic behind
  the arithmetic operators
  and added functionalities
• Calculations of the
  calculator can be carried
  out from both keyboard
  and the buttons on the calculator
• Skillful use of JDK
• Shows error messages
  for invalid calculations
• Object oriented development skills
• It implements:
1. ActionListener.
2. KeyListener.
3. TextListener.