Methods 4 Calculator

Note: This assignment is designed to focus you on RETURN VALUES.  Therefore it is a bit arbitrary in how I ask you to flow the numbers.

Create a new file called Assign4_Calculator.java.  

You are to write a looping calculator program that asks the user for a math operation (+,-,*,/, power) or the word exit.  It then calls a method that has been written for each operation.  It keeps a running total back in the Run function. (NOTE: Power function is quite hard and is only worth 10%. Consider skipping it if short of time.)

User’s View

Welcome to the calculator.

What is your starting number?

        7

What math operation do you want ( +, -, *, /, power, exit )         

        *

What is your next number?

        3

Your total is now 21.

What math operation do you want ( +, -, *, /, power, exit )         

        +

What is your next number?

        8

Your total is now 29

What math operation do you want ( +, -, *, /, power, exit )          

power

What is the exponent?

        3

Your total is now 24389

Super Important Hint of the Century:  

Your method calls must outlook like this:          firstnum = add(firstnum);

Your variable name can be different but you must save the result of the method back into the original number so it is updated for the next loop.

Methods required for 90%:

• public static double add(double firstNum ) 

• Inside: scan a second number, add them, return the result
• For each method, you can either print the result within the method or print it back in Run() after returning it. This is simply a design choice that I leave up to you.

• public static double subtract(double firstNum ) 

• Inside: scan a second number, subtract the second from the first, return the result

• public static double multiply(double firstNum ) 

• Inside: scan a second number, multiply them, return the result

• public static double divide(double firstNum ) 

• Inside: scan a second number, divide the first by the second, return the result
• If the user tries to divide by zero, it should NOT do the calculation.  Instead it should tell the user their error and give them another (or multiple) chances to enter the numbers.  There is a built in message where dividing by zero says “infinity”.  “Infinity” will not be accepted for this requirement.

Final 10% - Add a POWER function

• public static double power(double firstNum)
• Inside: ask the user for the exponent ,multiply the first number by itself that many times, return the result

• How do you do that?  Your first hint is that you need a FOR loop.

Hints for the Power Function:

public static double power(double firstNum){

double exponent - ask and scan for this number.

double newTotal = 1;       //create a new variable and set to ONE.

For loop(){

        Multiply newTotal by firstNum

}

Return newTotal