Assignment – Calculator with Methods The main method of your calculator program
ID: 3749010 • Letter: A
Question
Assignment – Calculator with Methods
The main method of your calculator program has started to get a little messy. In this assignment, you will clean it up some by moving some of your code into new methods. Methods allow you to organize your code, avoid repetition, and make aspects of your code easier to modify. While the calculator program is very simple, this assignment attempts to show you how larger, real world programs are structured. As a new programmer in a job, you will likely not be developing new programs by yourself, completely from scratch. Instead, it is likely that you will be asked to modify or write a new method within an existing program. It will help to ease your transition from school to work if you have been exposed to realistic program organization.
The new methods you will need to implement are listed below. While programming is often a very creative exercise, there are also times when you will need to be able to code to requirements such that what you write will integrate seamlessly with what other developers working on the same project will write. Because of this, for this assignment you will need to implement these methods with the exact signatures shown here.
public static int getMenuOption()
public static double getOperand(String prompt)
public static double add(double operand1, double operand2)
public static double subtract(double operand1, double operand2)
public static double multiply(double operand1, double operand2)
public static double divide(double operand1, double operand2)
public static double random(double lowerLimit, double upperLimit)
The getMenuOption method should display the menu to the user and read in their option. If the option is invalid, the method should inform the user and re-prompt them. This should continue until the user enters a valid option. Once the user has entered a valid choice, the getMenuOption method should return that choice to the calling method.
The getOperand method should display the prompt to the user and then read in a double value from the user. This value should be returned to the calling method. The intent is that you will be able to use this method to gather operands for both the standard arithmetic functions (add, subtract, multiply, and divide) and for the random number generation. For instance, in the case of subtract, you would do something like this:
double operand1 = getOperand(“What is the first number? “);
double operand2 = getOperand(“What is the second number? “);
// call your subtract method and pass it these inputs
For the case of random number generation, you would do something like this:
double lowerLimit = getOperand(“What is the lower limit? “);
double upperLimit = getOperand(“What is the upper limit? “);
// all your random number generation method and pass it these inputs
The add, subtract, multiply, divide, and random methods are pretty straightforward. For the divide method, if the second operand is zero, return the special value Double.NaN. This stands for “not a number.” We will discuss this more in later chapters.
Once you have written these new methods, rewrite the main method of your calculator program to use these methods whenever possible. The output (other than the special case of dividing by zero) should be identical to the output for last week.
Because you are reorganizing the program rather than adding any new functionality, your calculator should be able to pass the same tests that were included in the previous assignment (Third Assignment – Menu-Driven Calculator).
• You will be graded according to the following rubric (each item is worth one point):
• The getMenuOption method displays the options to the user, gets their choice, and returns it
• The getOperand method prints out the prompt that was passed in to the method, reads the double value the user enters in response, and returns it
• The add, subtract, multiply, and divide methods perform the corresponding mathematical operation.
• Division by zero causes the divide method to return Double.NaN
• The random method generates a random number between the lower and upper bounds passed to it and returns that number
• The main method uses the new methods you have developed whenever possible
• You program produces the correct output for all menu options
• Your program compiles
• Your program runs
• You follow standard coding conventions (e.g. variable names, indentation, comments, etc.)
• Note: If your program does not compile, you will receive a score of 0 on the entire assignment
• Note: If you program compiles but does not run, you will receive a score of 0 on the entire assignment
• Note: If your Eclipse project is not exported and uploaded to the eLearn drop box correctly, you will receive a score of 0 on the entire assignment
• Note: If you do not submit code that solves the problem for this particular assignment, you will not receive any points for the program’s compiling, the program’s running, or following standard coding conventions.
Here are some example runs of the program:
Menu
1. Add
2. Subtract
3. Multiply
4. Divide
5. Generate random number
6. Quit
What would you like to do? 9
I'm sorry, 9 wasn't one of the options
Menu
1. Add
2. Subtract
3. Multiply
4. Divide
5. Generate random number
6. Quit
What would you like to do? 0
I'm sorry, 0 wasn't one of the options
Menu
1. Add
2. Subtract
3. Multiply
4. Divide
5. Generate random number
6. Quit
What would you like to do? 7
I'm sorry, 7 wasn't one of the options Please try again later.
Menu
1. Add
2. Subtract
3. Multiply
4. Divide
5. Generate random number
6. Quit What would you like to do? 9
I'm sorry, 9 wasn't one of the options
Menu
1. Add
2. Subtract
3. Multiply
4. Divide
5. Generate random number
6. Quit
What would you like to do? 0
I'm sorry, 0 wasn't one of the options
Menu
1. Add
2. Subtract
3. Multiply
4. Divide
5. Generate random number
6. Quit
What would you like to do? 1
What is the first number? 3
What is the second number? 4
Answer: 7.0
Menu
1. Add
2. Subtract
3. Multiply
4. Divide
5. Generate random number
6. Quit
What would you like to do? 4
What is the first number? 6
What is the second number? 0
I'm sorry, you can't divide by zero.
Answer: NaN
Menu
1. Add
2. Subtract
3. Multiply
4. Divide
5. Generate random number
6. Quit
What would you like to do? 4
What is the first number? 6
What is the second number? 2
Answer: 3.0
Menu
1. Add
2. Subtract
3. Multiply
4. Divide
5. Generate random number
6. Quit
What would you like to do? 6
Goodbye!
Explanation / Answer
import java.util.Random;
import java.util.Scanner;
class calculator
{
public static int getMenuOption(){
int option;
while(true)
{
System.out.println("Menu 1. Add 2. Subtract 3. Multiply 4. Divide 5.Generate random number 6. Quit");
System.out.println("What would you like to do? ");
Scanner sc=new Scanner(System.in);
option=sc.nextInt();
if(option>0&&option<7)
return option;
else
System.out.println("I'm sorry, "+option+" wasn't one of the options");
}
}
public static double getOperand(String prompt){
System.out.println(prompt);
Scanner sc=new Scanner(System.in);
return sc.nextDouble();
}
public static double add(double operand1, double operand2){
return operand1+operand2;
}
public static double subtract(double operand1, double operand2){
return operand1-operand2;
}
public static double multiply(double operand1, double operand2){
return operand1*operand2;
}
public static double divide(double operand1, double operand2){
return operand1/operand2;
}
public static double random(double lowerLimit, double upperLimit){
Random r = new Random();
return (double)r.nextInt((int)(upperLimit-lowerLimit)) + lowerLimit;
}
public static void main(String[] args)
{
int option=getMenuOption();
double lowerLimit,upperLimit,operand1,operand2;
switch(option)
{
case 1:
operand1 = getOperand("What is the first number?");
operand2 = getOperand("What is the second number?");
System.out.println("Answer: "+add(operand1,operand2));
break;
case 2:
operand1 = getOperand("What is the first number?");
operand2 = getOperand("What is the second number?");
System.out.println("Answer: "+subtract(operand1,operand2));
break;
case 3:
operand1 = getOperand("What is the first number?");
operand2 = getOperand("What is the second number?");
System.out.println("Answer: "+multiply(operand1,operand2));
break;
case 4:
operand1 = getOperand("What is the first number?");
operand2 = getOperand("What is the second number?");
if(operand2==0){
System.out.println("I'm sorry, you can't divide by zero.");
System.out.println("Answer: NaN");
return;
} else {
System.out.println("Answer: "+divide(operand1,operand2));
}
break;
case 5:
lowerLimit = getOperand("What is the lower limit? ");
upperLimit = getOperand("What is the upper limit?");
System.out.println("Answer: "+random(lowerLimit,upperLimit));
break;
case 6:
System.out.println("Goodbye!");
break;
}
}
}
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