Problem
Open the Calculator.java file created for the Calculator application in this chapter. Modify the application to include buttons for Add to Memory (addM), Paste from Memory (pasteM), Backspace (Bksp), and Clear (CLR). Create a fifth row for the new buttons. Increase the length of the keys array. Construct each button and add the ActionListener to each of the new buttons. Then, in the action Performed() method, write a switch structure to search for each of the buttons. Write the code for each case.