Java method to convert hexadecimal to binary, and another method to convert binary to hexadecimal (no arrays, recursion, anything like that). Method declaration should be something like public static String hexadecimalToBinary(String hexadecimal) and vice versa.

Only hex input will be from 0-F, and only binary input will be from 0000 to 1111. so pls keep very simple. Input is a string and output is a string.