I am making a program that first asks the user to input a number from the console to choose which umber type they’d like to convert to the other two, after which the user enters a number in the form of a string which is converted to the other two systems also as a string. I’ve ran into a problem where the program just stops, not letting me input the string bin from the console.

package testing;

import java.util.Scanner;

public class TestingClass {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner sc = new Scanner(System.in);
        
        int num=0;
        for (;num!=4;) {
            System.out.println("1. Binary to hexadecimal and decimal");
            System.out.println("2. Hexidecimal to binary and decimal");
            System.out.println("3. Decimal to binary and hexadecimal");
            System.out.println("4. Exit");
            num = sc.nextInt();
            sc.nextLine();
            switch (num) {
                case 1: System.out.println("Enter a binary number");
                String bin = sc.nextLine();
                if (isBinary(bin)) {
                    String bin2 = binToHexAndDec(bin, true);
                    System.out.println(bin2);
                }
                else {
                    System.out.println("The number entered is not a binary number, please try again");
                }
                break;
                case 2: System.out.println("Enter a hexadecimal number");
                break;
                case 4:
                break;
                default:
                break;
        }
        }
    
    }
    public static String binToHexAndDec(String bin, boolean isHex) {
        String toHexAndDec = "";
        int decimal = 0;
        for (int i = bin.length()-1;i>=0;i--) {
            decimal += ((int)(bin.charAt(i)-'0'))*(Math.pow(10, i));
        }
        if (isHex) {
            for (;decimal!=0;); {
                if (decimal%16>9) {
                    char ch = (char)(decimal%16-9+'a');
                }
                else {
                    char ch = (char)(decimal%16+'0');
                }
                toHexAndDec += (char)(decimal%16+'0');
                decimal/=16;
            }
        }
        else {
            for (;decimal!=0;); {
                toHexAndDec += (char)(decimal%10+'0');
                decimal/=10;
            }
        }
        return toHexAndDec;
    }
    public static boolean isBinary(String bin) {
        boolean isBinary = true;
        for (int i =0;i<bin.length()||isBinary==false;i++) {
            char ch = bin.charAt(i);
            if (ch>'1'||ch<'0') {
                System.out.println("The number you entered is not a binary number, please try again");
                isBinary=false;
            }
        }
        return isBinary;
    }
}

I originally found a solution online using the implementation of sc.nextLine(); in between the num = sc.nextInt; for the switch and the String bin = sc.nextLine();. Before implementing sc.nextline; the program would entire skip over String bin = sc.nextLine(); but now the whole program comes to a halt. I rebuilt the whole program afterwards and learned that without calling the method isBinary() the String bin inputs successfully. I’m not sure why this is and I need to be able to call the method to convert the string to the other two number systems.