Develop a Calculator with a user interface that is virtually identical to this, excluding the menu shown.  Otherwise, your calculator should look like the one shown, and support all the operations shown. Note: if you have questions about what various buttons do, this is the calculator that is available on all Windows machines. Model your class as shown below:

1. A class representing the JCalculator. Here is a start for this class. Note that the JCalculator class extends JPanel, not JFrame.
2. Implement event handling using an inner class.
3. The buttons on the calculator must be implemented as an array of JButtons.
4. Test your Calculator class by compiling and executing the following class. You may not modify this class in any way.

Note: The three requirements below  must be met to get any credit for this assignment.

1. Your code must be formatted neatly. Eclipse can do this for you.
2. Your code must follow the conventions described here.
3. Add Javadoc comments to your code and generate the Javadoc file before submitting your assignment.

All the items above must be done to get any credit on the assignment.

Your assignment will be graded using the following rubric:

1. (30 points) User interface meets specifications. That is, your calculator looks pretty much like the calculator pictured. Note: I am concerned more about the layout of the buttons etc. than whether your buttons have rounded corners etc.
2. (70 points) Code is functional. 3.5 points for each of 20 functional elements.