Hex - functions

package com.company;
import java.util.*;

public class FunctionsHEX {
    HashMap<Integer, Character> decToHex = new HashMap<>();


        public static String fromBinToHex (String binary){
            int number = FunctionsBIN.fromBinToDec(binary.toCharArray());

            String hexString = "";
            int leftover;
            ArrayList<Integer> leftOvers = new ArrayList<>();


            HashMap<Integer, Character> decToHexValue = new HashMap<>();
            decToHexValue.put(0, '0');
            decToHexValue.put(1, '1');
            decToHexValue.put(2, '2');
            decToHexValue.put(3, '3');
            decToHexValue.put(4, '4');
            decToHexValue.put(5, '5');
            decToHexValue.put(6, '6');
            decToHexValue.put(7, '7');
            decToHexValue.put(8, '8');
            decToHexValue.put(9, '9');
            decToHexValue.put(10, 'A');
            decToHexValue.put(11, 'B');
            decToHexValue.put(12, 'C');
            decToHexValue.put(13, 'D');
            decToHexValue.put(14, 'E');
            decToHexValue.put(15, 'F');


            do {
                leftover = number % 16;
                number /= 16;

                leftOvers.add(leftover);

            } while (number > 0);


            for (int i = leftOvers.size() - 1; i >= 0; i--) {
                int integer = leftOvers.get(i);

                for (Map.Entry<Integer, Character> map : decToHexValue.entrySet()) {
                    if (integer == map.getKey()) {
                        hexString += map.getValue();
                    }
                }
            }


            return hexString;
        }


        public static char[] fromHexToBinary (String hex)
        {
            String binary = "";

            HashMap<Character, String> hexToBinValue = new HashMap<>();
            hexToBinValue.put('0', "0000");
            hexToBinValue.put('1', "0001");
            hexToBinValue.put('2', "0010");
            hexToBinValue.put('3', "0011");
            hexToBinValue.put('4', "0100");
            hexToBinValue.put('5', "0101");
            hexToBinValue.put('6', "0110");
            hexToBinValue.put('7', "0111");
            hexToBinValue.put('8', "1000");
            hexToBinValue.put('9', "1001");
            hexToBinValue.put('A', "1010");
            hexToBinValue.put('B', "1011");
            hexToBinValue.put('C', "1100");
            hexToBinValue.put('D', "1101");
            hexToBinValue.put('E', "1110");
            hexToBinValue.put('F', "1111");

            for (int i = 0; i < hex.length(); i++) {
                for (Map.Entry<Character, String> map : hexToBinValue.entrySet()) {
                    if (map.getKey().equals(hex.charAt(i))) {
                        binary += map.getValue();
                    }
                }
            }

            ArrayList<Character> characterArrayList = new ArrayList<>();

            for (int i = 0; i < binary.length(); i++) {
                characterArrayList.add(binary.charAt(i));
            }

            if (characterArrayList.get(0) == '0') {
                characterArrayList.remove(0);
            }

            char[] charArray = new char[characterArrayList.size()];

            for (int i = 0; i < charArray.length; i++) {
                charArray[i] = characterArrayList.get(i);
            }


            return charArray;
        }


        public static int lettersInHexNumber (String hex,int i, int counter){

            if (i < hex.length()) {
                if (hex.charAt(i) >= 65 && hex.charAt(i) <= 70) {
                    counter++;
                }
                i++;

                return lettersInHexNumber(hex, i, counter);
            }

            return counter;
        }

        public static String colorHexValueToDecimal (String hex){
            int red = 0;
            int green = 0;
            int blue = 0;


            for (int i = 0; i < 6; i += 2) {
                String str = hex.substring(i, i + 2);

                if (i < 2) {
                    red = FunctionsBIN.fromBinToDec(fromHexToBinary(str));
                } else if (i >= 2 && i < 4) {
                    green = FunctionsBIN.fromBinToDec(fromHexToBinary(str));
                } else {
                    blue = FunctionsBIN.fromBinToDec(fromHexToBinary(str));
                }
            }


            return "rgb(" + red + ", " + green + ", " + blue + ')';

        }
    }