Manual Code For Converting Binary Octa / Hexa And Decimal

There's a main menu choosing binary,octa,hexa,and decimal if i choose decimal it will display decimal menu and then i will input the numbers of binary and then it automatically display the converting process for octa hexa and decimal. and if i choose octa . It display the octa menu and i will input the numbers in octa and then it automatically display the converting process for binary hexa and decimal.. and so on.. but in binary if i input 2 it will display invalid .. the same as octa hexa and decimal... in my code the only problem is the converting process. our instructor said no one will use a converter for our project. we will code it manually ..so for a moment .. this is my code..

import java.util.*;
import java.lang.*;
public class mainmenu {
public static void main (String[]args) {
Scanner in = new Scanner(System.in);
char B, O, H, D, Q, L, N , Y;
char bin , pk, pick ;

[code]....