java中十进制转二进制二进制转十进制、十进制转十六进制、十六进制转十进制的程序

Question

i am supposed to write a java program that converts binary to decimal, decimal to binary, decimal to hexadecimal and hexadecimal to decimal. i have done the first to parts using a switch case and it works now I am stuck on the last two. here is what I have so far.

package java_project_gabriel;

import java.util.Scanner;


public class BinaryToDecimal {

    public String toBinary(int n) {
        if (n == 0) {
            return "0";
        }
        String binary = "";
        while (n > 0) {
            int rem = n % 2;
            binary = rem + binary;
            n = n / 2;
        }
        return binary;
    }

    public int binaryTodecimal(int i) {
        int n = 0;
        for (int pow = 1; i > 0; pow *= 2, i /= 10)
            n += pow * (i % 10);
        return n;
    }
   

    public static void main(String[] args) {

        int answer2 = 0;
        String answer;

        final int info = 10;
        for (int i = 0; i < info; i++) {

            Scanner kb = new Scanner(System.in);
            System.out.println("==================================");
            System.out.print("Enter your choice: ");
            answer = kb.next();

            switch (answer) {
            case "1": // if the answer is one do this action
                System.out.print("Enter a number: ");
                answer2 = kb.nextInt();
                BinaryToDecimal decimalToBinary = new BinaryToDecimal();
                String binary = decimalToBinary.toBinary(answer2);
                System.out.println("The 8-bit binary representation is: " + binary);
                break; // leave the switch 

            case "2": // if answer is 2 do the following actions
                System.out.print("Enter a number: ");
                answer2 = kb.nextInt();
                BinaryToDecimal bd = new BinaryToDecimal();
                int n = bd.binaryTodecimal(answer2);
                System.out.println("The decimal representation is: " + n);
                break; // leave the switch case
                

          
            case "3": // when the answer is 3
                System.out.println("Goodbye");
                System.exit(0);
                // break; you need not use here because you have an exit call

            }
        }
    }
}

Answer 1

Decimal -> Hexa :

public static String toHex(int decimal) {
        int rem = 0;
        String hex = (decimal == 0 ? "0" : "");
        String hexstring = "0123456789ABCDEF";
        while (decimal > 0) {
            rem = decimal % 16;
            hex = hexstring.charAt(rem) + hex;
            decimal /= 16;
        }
        return hex;
    }

Hexa -> Decimal :

public static int toDecimal(String hex) {
        String hexstring = "0123456789ABCDEF";
        hex = hex.toUpperCase();
        int num = 0;
        for (int i = 0; i < hex.length(); i++) {
            char ch = hex.charAt(i);
            num = 16 * num + hexstring.indexOf(ch);
        }
        return num;
    }