issue with user defined methods executing

Question

Code no longer runs as I can't figure out how to get the scanner to run, but how do I get the methods to execute? Tips and help is appreciated. Thanks in advance.

For clarification, I want this code to run like a geometry calculator, however I do not really know how to call methods (which I think is the issue here)

import java.util.Scanner;
import java.lang.Math;


public class Geometry
{
        private static void printMenu()
    {
                System.out.println("This is a geometry calculator");
                System.out.println("Choose what you would like to calculate");
                System.out.println("1. Find the area of a rectangle");
                System.out.println("2. Find the perimeter of a rectangle");
                System.out.println("3. Find the perimeter of a triangle");
                System.out.println("Enter the number of your choice:");
    }

 public static void main (String [] args)
 {
  int choice;   //the user's choice
  double value = 0; //the value returned from the method
  char letter;  //the Y or N from the user's decision to exit
  double radius;  //the radius of the circle
  double length;  //the length of the rectangle
  double width;  //the width of the rectangle
  double height;  //the height of the triangle
  double base;  //the base of the triangle
  double side1;  //the first side of the triangle
  double side2;  //the second side of the triangle
  double side3;  //the third side of the triangle

  Scanner keyboard = new Scanner (System.in);
 }

    public static double rectangleArea(double length, double width, double value, Scanner keyboard) {
     System.out.print("Enter the length of the rectangle:  ");
     length = keyboard.nextDouble();
     System.out.print("Enter the width of the rectangle:  ");
     width = keyboard.nextDouble();
     value= length*width;
     System.out.println("The area of a rectangle is " + value);
     return value;
    }

    public static double rectanglePerimeter(double length, double width, double value, Scanner keyboard) {
     System.out.print("Enter the length of the rectangle:  ");
     length = keyboard.nextDouble();
     System.out.print("Enter the width of the rectangle:  ");
     width = keyboard.nextDouble();
     value= (2*length)+(2*width);
     System.out.println("The perimeter of the rectangle is " + value);
     return value;
    }

    public static double trianglePerimeter(double side1, double side2, double side3, double value, Scanner keyboard) {
     System.out.print("Enter the length of side 1 of the triangle:  ");
     side1 = keyboard.nextDouble();
     System.out.print("Enter the length of side 2 of the triangle:  ");
     side2 = keyboard.nextDouble();
     System.out.print("Enter the length of side 3 of the triangle:  ");
     side3 = keyboard.nextDouble();
     //call the perimeter method and store the result in the value variable
     value = (side1 + side2 + side3);
     System.out.println("The perimeter of the triangle is " + value);
     return value;

    //default:
     //System.out.println("You did not enter a valid choice.");
    }
}

I think OP wants to move the entire `switch`/`case` statement into another `static` method. — But I'm Not A Wrapper Class, Oct 27 '14 at 15:04
Yes sorry, I want all 3 mathematical switches to separate static methods — Gianna Caruso, Oct 27 '14 at 15:05
Also, if you're looking to add additional functionality, I strongly recommend that you start using separately defined classes for each shape with a parent 'shape' class (or interface). — FelixMarcus, Oct 27 '14 at 15:07
write separate methods for each mathematical functions and then call appropriate method in your switch case. — BDRSuite, Oct 27 '14 at 15:08
Please learn a basic Java tutorial before attempting to write any programs in it. You will learn how to format code and do basic things that you are asking SO for. — bcsb1001, Oct 27 '14 at 15:23

Grice · Answer 1 · 2014-10-27T15:29:03.120

3

I'm assuming you just want to encapsulate each of your cases in methods. Simply create a new method for each.

Example for case 2:

private static double rectanglePerimeter(Scanner keyboard) {
     System.out.print("Enter the length of the rectangle:  ");
     double length = keyboard.nextDouble();
     System.out.print("Enter the width of the rectangle:  ");
     double width = keyboard.nextDouble();
     double value= (2*length)+(2*width);
     System.out.println("The perimeter of the rectangle is " + value);
     return value;
}

In your case block you would invoke it like:

switch (choice)
   {
    case 1:
     value = rectangleArea(keyboard);
     break;
    case 2:
     value = rectanglePerimeter(keyboard);
     break;
    case 3:
     value = trianglePerimeter(keyboard);
     break;
}

You can then refactor some of the variables out of main, such as length and width

edited Oct 27 '14 at 15:29

answered Oct 27 '14 at 15:09

Grice

1,345
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24

This was upvoted before it was even a working solution :/ – But I'm Not A Wrapper Class Oct 27 '14 at 15:13
I'm about to post an updated version of the code – Gianna Caruso Oct 27 '14 at 15:19
@GiannaCaruso Regarding your edited code, your don't nest your methods within your main, you invoke them within your switch statement. You still need to include your swtich/case structure. – Grice Oct 27 '14 at 15:24
I can't call the methods in the main and avoid a switch all together? @Grice – Gianna Caruso Oct 27 '14 at 15:25
@GiannaCaruso You need a switch so that it knows what methods to invoke. Your simply moving the calculations out into separate methods. – Grice Oct 27 '14 at 15:26

But I'm Not A Wrapper Class · Answer 2 · 2014-10-27T15:48:33.673

Example method:

public static double calculateRectangleArea(Scanner keyboard){
    System.out.print("Enter the length of the rectangle:  ");
    double length = keyboard.nextDouble();
    System.out.print("Enter the width of the rectangle:  ");
    double width = keyboard.nextDouble();
    double value= length*width;
    System.out.println("The area of a rectangle is " + value);
    return value;
}

Example call:

case 1:
    value = calculateRectangleArea(keyboard);
    break;

Make sure to pass the Scanner. You can do these for the other two cases.

So it should look more like this in the end:

import java.util.Scanner;
import java.lang.Math;

public class Geometry
{
    private static void printMenu()
    {
        System.out.println("This is a geometry calculator");
        System.out.println("Choose what you would like to calculate");
        System.out.println("1. Find the area of a rectangle");
        System.out.println("2. Find the perimeter of a rectangle");
        System.out.println("3. Find the perimeter of a triangle");
        System.out.println("Enter the number of your choice:");
    }

    public static double calculateRectangleArea(Scanner keyboard){
        System.out.print("Enter the length of the rectangle:  ");
        double length = keyboard.nextDouble();
        System.out.print("Enter the width of the rectangle:  ");
        double width = keyboard.nextDouble();
        double value = length*width;
        System.out.println("The area of a rectangle is " + value);
        return value;
    }

    public static double calculateRectanglePerimeter(Scanner keyboard){
        System.out.print("Enter the length of the rectangle:  ");
        double length = keyboard.nextDouble();
        System.out.print("Enter the width of the rectangle:  ");
        double width = keyboard.nextDouble();
        double value = (2*length)+(2*width);
        System.out.println("The perimeter of the rectangle is " + value);
        return value;
    }

    public static double calculateTrianglePerimeter(Scanner keyboard){
        System.out.print("Enter the length of side 1 of the triangle:  ");
        double side1 = keyboard.nextDouble();
        System.out.print("Enter the length of side 2 of the triangle:  ");
        double side2 = keyboard.nextDouble();
        System.out.print("Enter the length of side 3 of the triangle:  ");
        double side3 = keyboard.nextDouble();
        //call the perimeter method and store the result in the value variable
        double value = (side1 + side2 + side3);
        System.out.println("The perimeter of the triangle is " + value);
        return value;
    }

    public static void main (String [] args)
    {
        int choice;   //the user's choice
        char letter;  //the Y or N from the user's decision to exit
        double value;
        Scanner keyboard = new Scanner (System.in);

        do
        {
            //call the printMenu method
            printMenu();
            choice = keyboard.nextInt();

            switch (choice)
            {
                case 1:
                    value = calculateRectangleArea(keyboard);
                    break;
                case 2:
                    value = calculateRectanglePerimeter(keyboard);
                    break;
                case 3:
                    value = calculateTrianglePerimeter(keyboard);
                    break;
                default:
                    System.out.println("You did not enter a valid choice.");
            }

            keyboard.nextLine(); //consumes the new line character after the number
            System.out.println("Do you want to exit the program (Y/N)?:  ");
            String answer = keyboard.nextLine();
            letter = answer.charAt(0);
        }while (letter != 'Y' && letter != 'y');
    }
}

Okay, now the calls should be in a separate switch statement? — Gianna Caruso, Oct 27 '14 at 15:22
This is helpful but I don't think I want void methods, I want them to return a value — Gianna Caruso, Oct 27 '14 at 15:47

issue with user defined methods executing

2 Answers2