Question

I am having trouble getting my menu below to run from my driver. The program will execute, however it will not display my menu until I enter a number. After that it will display properly, and it reads selection properly, but will not call the methods I have listed in the case statement.

For instance, if I input a ‘1’, the menu will recognize I input a 1 and will display the menu again with “You entered 1”. instead of calling dec.getDec(), as it should according to the case statement. Any helpful hints or advice would be appreciated. This is a homework assignment, and I am not trying to get someone to write the code for me or anything. I just need to be pointed in the right direction please.

import java.io.IOException;
import java.io.*;
import java.util.Scanner;

public class Menu {
    Scanner scan = new Scanner(System.in); 
    int selection;

    public int GetSelection()
   {
       selection = scan.nextInt();
       return selection;
   }

    public void display()
    {

          System.out.println("Please choose an option from the following:"); 
          System.out.println("[1] Convert Decimal to Binary"); 
          System.out.println("[2] Convert Decimal to Hexadecimal"); 
          System.out.println("[3] Convert Binary to Decimal"); 
          System.out.println("[4] Convert Binary to Hexadecimal"); 
          System.out.println("[5] Convert Hexadecimal to Decimal"); 
          System.out.println("[6] Convert Hexadecimal to Binary"); 
          System.out.println("[0] Exit");

          System.out.println("\n");
          System.out.println("You entered: " + selection);
   }

}


----------------------------
import java.io.*;
import java.lang.*;
import java.util.Scanner;


public class Driver
{

    public static void main(String[] args)throws IOException {

            LineWriter lw = new LineWriter("csis.txt");
            int selection;

            Decimal dec = new Decimal();
            Binary bin = new Binary();
            Hexadecimal hex = new Hexadecimal();
            Menu menu = new Menu();


        do{ 
            menu.display();

            selection=menu.GetSelection();

            switch (selection){

            case '1':{ dec.getDec();
                      break;}
            case '2':{ dec.getHex();
                      break;}
            case '3':{ bin.getBin();
                      break;}
            case '4':{ bin.getHex();
                      break;}
            case '5':{ hex.getHex();
                      break;}
            case '6': { hex.getDec();
                      break;  }     
            //default: System.out.println("Error: Unrecognized Selection");
            //          break;

           }
        }while (selection !=0);
    }   
}

Answer 1

As this is homework, I won’t give you the whole solution, but I’ll help get you there…

Your problem is coming from your use of Scanner, the helpful part of this page is A scanning operation may block waiting for input.

Using that you should be able to see where the problem is, if you need more help comment on this answer and I’ll see if there’s more I can do.