Chapter 9, Problem 2PP

Write a program that uses the class calculator in Listing 9.12 to create a more powerful calculator. This calculator will allow you to save one result in memory and call the result back. The commands the calculator takes are

• e for end
• c for Clear; sets result to zero
• m for save in memory; sets memory equal to result
• r for recall memory; displays the value of memory but does not change result

You should define a derived class of the class calculator that has one more instance variable for the memory, a new main method that runs the improved calculator, a redefinition of the method hanndleUnknownOpException, and anything else new or redefined that you need. A sample interaction with the user is shown next. Your program need not produce identical output, but it should be similar and just as clear or even clearer.

Calculator on: result = 0.0

+ 4

result + 4.0 = 4.0

updated result =4.0

/ 2

result / 2.0 = 2.0

updated result =2.0

m

result saved in memory

c

result = 0.0

+ 99

result + 99.0 = 99.0

updated result = 99.0

/ 3

result / 3.0 = 33.0

updated result =33.0

r

recalled memory value = 2.0

result =33.0

+ 2

result: + 2.0 = 35.0

updated result = 35.0

e

End of program