import java.util.Scanner; import java.util.Arrays; import java.util.List; import java.util.ArrayList; import java.util.Iterator; import java.lang.Math; import java.util.Collections; import java.util.HashMap; public class Program { public static void main(String[] args){ /* //////////////////////////////////////// ENTER hex, bin OR dec AS STARTVALUE ENTER ACTUAL VALUE GET RESULTS //////////////////////////////////////// */ try{ Scanner read = new Scanner(System.in); System.out.println("Enter the type of number you want to convert (hex/bin/dec)"); String choice = read.next(); switch(choice){ case "hex": System.out.println("Enter a hexadecimal number"); String hexa = read.next(); checkHexa(hexa); System.out.println("Hexadecimal notation : " + hexa); System.out.println("Decimal notation : " + hexDec(hexa)); System.out.println("Binary notation : " + hexBin(hexa)); break; case "dec": System.out.println("Enter a decimal number"); int decimal = Integer.parseInt(read.next()); System.out.println("Decimal notation : " + decimal); System.out.println("Binary notation : " + decBin(decimal)); System.out.println("Hexadecimal notation : " + decHex(decimal)); break; case "bin": System.out.println("Enter a binary"); int binary = Integer.parseInt(read.next()); System.out.println("Binary notation : " + binary); System.out.println("Decimal notation : " + binDec(binary)); System.out.println("Hexadecimal notation : " + binHex(binary)); break; default: System.out.println("choose one of the 3 choices \n(hex/bin/dec) " + choice); } } catch(Exception ex){ System.out.println("woopsie " + ex.getMessage()); } } /* Converts decimal to hexadecimal */ public static String decHex(int number){ if(number < 16){ return hexNum(number); } else{ return decHex(number/16) + hexNum(number%16); } } /* Converts decimal numbers to hexadecimal numbers */ public static String hexNum(int num){ String result; switch(num){ case 10: result = "A"; break; case 11: result = "B"; break; case 12: result = "C"; break; case 13: result = "D"; break; case 14: result = "E"; break; case 15: result = "F"; break; default: result = "" + num; break; } return result; } /* Converts decimals to binary */ private static String decBin(int number){ if(number%2 == 1){ if(number == 1){ return "1"; } else{ return decBin(number/2) + "1"; } } else{ return decBin(number/2) + "0"; } } /* check if input = binary */ private static void checkBin(int[] bin) throws Exception { for(int t: bin){ if(t>1){ throw new Exception("enter a binary number"); } } } /* Binary to decimal */ private static String binDec(int binary) throws Exception { try{ String sBinar = Integer.toString(binary); int[] split = new int[sBinar.length()]; for(int c= sBinar.length()-1; c>= 0; c--){ split[c] = sBinar.charAt(c)-'0'; } checkBin(split); int multi = 1; int result = 0; for(int i = sBinar.length()-1; i>=0; i--){ result += split[i]*multi; multi*= 2; } return Integer.toString(result); } catch (Exception ex){ throw new Exception(ex.getMessage()); } } /* binary to hexadecimal */ private static String binHex(int binary) throws Exception { String sBinar = Integer.toString(binary); int[] split = new int[sBinar.length()]; for(int c= sBinar.length()-1; c>= 0; c--){ split[c] = sBinar.charAt(c)-'0'; } int multi = 1; int counter = 0; int result = 0; List results = new ArrayList (); for(int i = sBinar.length()-1; i>=0; i--){ counter++; result += split[i]*multi; multi*=2; if(counter == 4|| i==0){ results.add(hexNum(result)); multi = 1; counter = 0; result = 0; } } Collections.reverse(results); String total = ""; for(Iterator i = results.iterator(); i.hasNext(); ){ String s = i.next(); total+= s; } return total; } /* Check if hexadecimal */ private static void checkHexa(String hex) throws Exception{ char[] arrHex; arrHex = hex.toCharArray(); for(char c: arrHex){ if(!((c>= 48 && c<=57)||(c>=65 && c<=90))){ throw new Exception("this is not a valid hexadecimal number"); } } } /* hexadecimal numbers to decimal numbers */ private static int toDec(char hexn){ String returnNumber; switch(hexn){ case 'A': returnNumber = "10"; break; case 'B': returnNumber = "11"; break; case 'C': returnNumber = "12"; break; case 'D': returnNumber = "13"; break; case 'E': returnNumber = "14"; break; case 'F': returnNumber = "15"; break; default: returnNumber="" + hexn; } return Integer.parseInt(returnNumber); } /* hexadecimal to decimal */ private static String hexDec(String hex){ char[] arrHex; arrHex = hex.toCharArray(); int result = 0; List arrDec = new ArrayList (); for(int e = 0; e i = arrDec.iterator(); i.hasNext(); ){ int num = i.next(); result += num*(Math.pow(16, counter)); counter++; } return Integer.toString(result); } /* hexadecimal to binary */ private static String hexBin(String hexadec){ char[] arrayH; arrayH = hexadec.toCharArray(); HashMap dict = new HashMap(); String result = ""; dict.put('1',"0001"); dict.put('2',"0010"); dict.put('3',"0011"); dict.put('4',"0100"); dict.put('5',"0101"); dict.put('6', "0110"); dict.put('7', "0111"); dict.put('8', "1000"); dict.put('9', "1001"); dict.put('A', "1010"); dict.put('B', "1011"); dict.put('C', "1100"); dict.put('D', "1101"); dict.put('E', "1110"); dict.put('F', "1111"); for(char c: arrayH){ result += dict.get(c); } return result; } }

converter decimal <-> hexadecimal <-> binary