Conversions class

/*
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 */
package converter;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.Scanner;
import javafx.scene.input.KeyCode;

/**
 *
 * @author Acer
 */
public class Conversions {

    @Checked
    public static String decimalToBinary(String decimal){
        if(decimal.length() == 0)
            return "";
        for(int i = 0;i < decimal.length();i++)
            if(!Utilities.isDecimalDigit(decimal.charAt(i)))
                return "Error!";
        if(decimal.charAt(0) == '-')
            return Long.toBinaryString(Long.parseLong(decimal));
        switch(decimal){
            case "0":
                return "0";
            case "1":
                return "1";
            default:
                long value = Long.parseLong(decimal);
                String rep = "";
                while(value > 0){
                    rep += (value % 2);
                    value /= 2;
                }
                return Utilities.reverse(rep);
        }
    }

    @Checked
    public static String decimalToOctal(String decimal){
        if(decimal.length() == 0)
            return "";
        for(int i = 0;i < decimal.length();i++)
            if(!Utilities.isDecimalDigit(decimal.charAt(i))){
                System.out.println("Error in decimalToOctal");
                return "Error!";
            }
        if(decimal.charAt(0) == '-')
            return Long.toOctalString(Long.parseLong(decimal));
        switch(decimal){
            case "0":
                return "0";
            case "1":
                return "1";
            case "2":
                return "2";
            case "3":
                return "3";
            case "4":
                return "4";
            case "5":
                return "5";
            case "6":
                return "6";
            case "7":
                return "7";
            default:
                long value = Long.parseLong(decimal);
                String rep = "";
                while(value > 0){
                    rep += (value % 8);
                    value /= 8;
                }
                return Utilities.reverse(rep);
        }
    }

    @Checked
    public static String decimalToHexadecimal(String decimal){
        if(decimal.length() == 0)
            return "";
        for(int i = 0;i < decimal.length();i++)
            if(!Utilities.isDecimalDigit(decimal.charAt(i))){
                System.out.println("Error in decimalToHexadecimal");
                return "Error!";
            }
        if(decimal.charAt(0) == '-')
            return Long.toHexString(Long.parseLong(decimal));
        switch(decimal){
            case "0":
                return "0";
            case "1":
                return "1";
            case "2":
                return "2";
            case "3":
                return "3";
            case "4":
                return "4";
            case "5":
                return "5";
            case "6":
                return "6";
            case "7":
                return "7";
            case "8":
                return "8";
            case "9":
                return "9";
            case "10":
                return "A";
            case "11":
                return "B";
            case "12":
                return "C";
            case "13":
                return "D";
            case "14":
                return "E";
            case "15":
                return "F";
            default:
                long value = Long.parseLong(decimal);
                String rep = "";
                while(value > 0){
                    rep += Utilities.toHexadecimalDigit((int) (value % 16));
                    value /= 16;
                }
                return Utilities.reverse(rep);
        }
    }

    @Checked
    public static String binaryToDecimal(String binary){
        if(binary.length() == 0)
            return "";
        for(int i = 0;i < binary.length();i++)
            if(!Utilities.isBinaryDigit(binary.charAt(i)))
                return "Error!";
        switch(binary){
            case "0":
                return "0";
            case "1":
                return "1";
            default:
                binary = Utilities.reverse(binary);
                long result = 0;
                for(int i = 0;i < binary.length();i++)
                    if(binary.charAt(i) != '0')
                        result += (long) Math.pow(2, i);
                return String.valueOf(result);
        }
    }

    @Checked
    public static String binaryToOctal(String binary){
        if(binary.length() == 0)
            return "";
        for(int i = 0;i < binary.length();i++)
            if(!Utilities.isBinaryDigit(binary.charAt(i)))
                return "Error!";
        switch(binary){
            case "0":
                return "0";
            case "1":
                return "1";
            default:
                return decimalToOctal(binaryToDecimal(binary));
        }
    }

    @Checked
    public static String binaryToHexadecimal(String binary){
        if(binary.length() == 0)
            return "";
        for(int i = 0;i < binary.length();i++)
            if(!Utilities.isBinaryDigit(binary.charAt(i)))
                return "Error!";
        switch(binary){
            case "0":
                return "0";
            case "1":
                return "1";
            default:
                return decimalToHexadecimal(binaryToDecimal(binary));
        }
    }

    @Checked
    public static String octalToDecimal(String octal){
        if(octal.length() == 0)
            return "";
        for(int i = 0;i < octal.length();i++)
            if(!Utilities.isOctalDigit(octal.charAt(i))){
                System.out.println("Error in decimalToHexadecimal");
                return "Error!";
            }
        switch(octal){
            case "0":
                return "0";
            case "1":
                return "1";
            case "2":
                return "2";
            case "3":
                return "3";
            case "4":
                return "4";
            case "5":
                return "5";
            case "6":
                return "6";
            case "7":
                return "7";
            default:
                octal = Utilities.reverse(octal);
                long result = 0;
                Iterator<Character> it = Utilities.stringIterator(octal);
                int x = 0;
                while(it.hasNext())
                    result += (long) Math.pow(8, x++) * Character.digit(it.next(), 10);
                return String.valueOf(result);
        }
    }

    @Checked
    public static String octalToBinary(String octal){
        if(octal.length() == 0)
            return "";
        for(int i = 0;i < octal.length();i++)
            if(!Utilities.isOctalDigit(octal.charAt(i)))
                return "Error!";
        switch(octal){
            case "0":
                return "0";
            case "1":
                return "1";
            default:
                ArrayList<StringBuilder> groups = new ArrayList<>();
                for(int i = 0;i < octal.length();i++){
                    StringBuilder current = new StringBuilder( decimalToBinary(String.valueOf(octal.charAt(i))) );
                    if(i > 0){
                        while(current.length() < 3)
                            current.insert(0, '0');
                    }
                    groups.add(current);
                }
                String result = "";
                result = groups.stream().map((elem) -> elem.toString()).reduce(result, String::concat);
                return result;
        }
    }

    @Checked
    public static String octalToHexadecimal(String octal){
        return decimalToHexadecimal( octalToDecimal(octal) );
    }

    @Checked
    public static String hexadecimalToDecimal(String hex){
        if(hex.length() == 0)
            return "";
        for(int i = 0;i < hex.length();i++)
            if(!Utilities.isHexadecimalDigit(hex.charAt(i))){
                System.out.println("Error in hexadecimalToDecimal");
                return "Error!";
            }
        switch(hex){
            case "0":
                return "0";
            case "1":
                return "1";
            case "2":
                return "2";
            case "3":
                return "3";
            case "4":
                return "4";
            case "5":
                return "5";
            case "6":
                return "6";
            case "7":
                return "7";
            case "8":
                return "8";
            case "9":
                return "9";
            case "A":
            case "a":
                return "10";
            case "B":
            case "b":
                return "11";
            case "C":
            case "c":
                return "12";
            case "D":
            case "d":
                return "13";
            case "E":
            case "e":
                return "14";
            case "F":
            case "f":
                return "15";
            default:
                hex = Utilities.reverse(hex);
                long result = 0;
                for(int i = 0;i < hex.length();i++)
                    result += (long) (Math.pow(16, i) * Utilities.toDecimalValue(hex.charAt(i)));
                return String.valueOf(result);
        }
    }

    @Checked
    public static String hexadecimalToBinary(String hex){
        if(hex.length() == 0)
            return "";
        for(int i = 0;i < hex.length();i++)
            if(!Utilities.isHexadecimalDigit(hex.charAt(i)))
                return "Error!";
        switch(hex){
            case "0":
                return "0";
            case "1":
                return "1";
            default:
                ArrayList<StringBuilder> groups = new ArrayList<>();
                for(int i = 0;i < hex.length();i++){
                    StringBuilder current = new StringBuilder( decimalToBinary( String.valueOf( Utilities.toDecimalValue(hex.charAt(i)) ) ) );
                    if(i > 0){
                        while(current.length() < 4)
                            current.insert(0, '0');
                    }
                    groups.add(current);
                }
                String result = "";
                result = groups.stream().map((elem) -> elem.toString()).reduce(result, String::concat);
                return result;
        }
    }

    @Checked
    public static String hexadecimalToOctal(String hex){
        return decimalToOctal( hexadecimalToDecimal(hex) );
    }
}