ChoiceMenu.java

import java.util.Scanner;
 
public class ChoiceMenu
{
   
                                                                                                                                                                                                                       
    public void display()
    {
            System.out.println ();
            System.out.println ("Please enter selection (1-7)");
            System.out.println ("[1]Decimal to Binary");
            System.out.println ("[2]Decimal To Hexidecimal");
            System.out.println ("[3]Binary To Decimal");
            System.out.println ("[4]Binary To Hexidecimal");
            System.out.println ("[5]exidecimal To Binary");
            System.out.println ("[6]Hexidecimal To Decimal");
            System.out.println ("[7]Exit program" );
    }
   
    public int getSelection()
    {
        Scanner kb = new Scanner(System.in);
        int choice;
        do { // Enhanced Menu input handling - checks that the input is in the valid range
            System.out.println( "Please enter selection (1-7):");
            choice = kb.nextInt();
        } while ((choice < 1) || (choice > 7)); 
        kb.close();  // Close the Scanner when no longer needed
        return choice;
    }
   
}

Decimal.java

public class Decimal {
	// instance variables - replace the example below with your own
	private static final String HEX_DIGITS = "0123456789ABCDEF";

	public String toBin(int numberToConvert) {
		StringBuilder sb = new StringBuilder();
		int remain;
		int denom = 2;
		int quot;
		int num = numberToConvert;
		while (num != 0) {
			quot = num / denom;
			remain = num % denom;

			sb.insert(0, remain);

			num = quot;

		}
		return sb.toString();
	}

	public String toHex(int numberToConvert) {
		StringBuilder sb = new StringBuilder();
		int num = numberToConvert;
		int remain;
		int quot;
		int denom = 16;
		char hexRemain;
		while (num != 0) {
			quot = num / denom;
			remain = num % denom;

			hexRemain = HEX_DIGITS.charAt(remain);

			sb.insert(0, hexRemain);

			num = quot;
		}
		return sb.toString();
	}

}

Driver.java

// import java.awt.Menu; // This import resulted from a name conflict
// import java.io.FileWriter;
// import java.io.IOException;
// import java.io.PrintWriter;
import java.util.Scanner;

public class Driver {

	public static int getANumber() {
		Scanner kbd = new Scanner(System.in);
		int num = kbd.nextInt();
		kbd.close();
		return num;
	}

	public static void main(String [] args) {
        int choice;
       
        // PrintWriter pw = new PrintWriter (new FileWriter("csis.txt")); // Could be removed
        Decimal dec = new Decimal(); /*
        Binary bin = new Binary();
        Hexadecimal hex = new Hexadecimal(); */
        ChoiceMenu menu = new ChoiceMenu();
       
        do{
            menu.display();
            choice = menu.getSelection();
            switch (choice) {
                case 1 : {
                  // Here, a method to retrieve a number for the conversion should go,
                  // then the conversion should be called with the number as parameter,
                  // then the result should be output
                  System.out.println("Input Decimal number to be converted:");
                  int numberToConvert = getANumber();
                  System.out.println("Decimal: " + numberToConvert);
                  System.out.println("Binary: " + dec.toBin(numberToConvert));
                }
                case 2 :  {
                    // Here, a method to retrieve a number for the conversion should go,
                    // then the conversion should be called with the number as parameter,
                    // then the result should be output
                    System.out.println("Input Decimal number to be converted:");
                    int numberToConvert = getANumber();
                    System.out.println("Decimal: " + numberToConvert);
                    System.out.println("Hexadecimal: " + dec.toHex(numberToConvert));
                  }/*
                case 3 : bin.binToDec(); break;
                case 4 : bin.binToHex(); break;
                case 5 : hex.hexToBin(); break;
                case 6 : hex.hexToDec(); break;*/
            }
        }while (choice != 7);
        // pw.close();
    }
}