Converting A String To Hexadecimal In Java

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I am trying to convert a string like "testing123" into hexadecimal form in java. I am currently using BlueJ.

And to convert it back, is it the same thing except backward?

hex java string
23 Answers

Here's a short way to convert it to hex:

public String toHex(String arg) {
    return String.format("%040x", new BigInteger(1, arg.getBytes(/*YOUR_CHARSET?*/)));
}
user_1038420

The numbers that you encode into hexadecimal must represent some encoding of the characters, such as UTF-8. So first convert the String to a byte[] representing the string in that encoding, then convert each byte to hexadecimal.

public static String hexadecimal(String input, String charsetName) throws UnsupportedEncodingException {
    if (input == null) throw new NullPointerException();
    return asHex(input.getBytes(charsetName));
}

private static final char[] HEX_CHARS = "0123456789abcdef".toCharArray();

public static String asHex(byte[] buf)
{
    char[] chars = new char[2 * buf.length];
    for (int i = 0; i < buf.length; ++i)
    {
        chars[2 * i] = HEX_CHARS[(buf[i] & 0xF0) >>> 4];
        chars[2 * i + 1] = HEX_CHARS[buf[i] & 0x0F];
    }
    return new String(chars);
}
spdenne_117210

Here an other solution

public static String toHexString(byte[] ba) {
    StringBuilder str = new StringBuilder();
    for(int i = 0; i < ba.length; i++)
        str.append(String.format("%x", ba[i]));
    return str.toString();
}

public static String fromHexString(String hex) {
    StringBuilder str = new StringBuilder();
    for (int i = 0; i < hex.length(); i+=2) {
        str.append((char) Integer.parseInt(hex.substring(i, i + 2), 16));
    }
    return str.toString();
}
user_10788830

I would suggest something like this, where str is your input string:

StringBuffer hex = new StringBuffer();
char[] raw = tokens[0].toCharArray();
for (int i=0;i<raw.length;i++) {
    if     (raw[i]<=0x000F) { hex.append("000"); }
    else if(raw[i]<=0x00FF) { hex.append("00" ); }
    else if(raw[i]<=0x0FFF) { hex.append("0"  ); }
    hex.append(Integer.toHexString(raw[i]).toUpperCase());
}
user_1123080 
byte[] bytes = string.getBytes(CHARSET); // you didn't say what charset you wanted
BigInteger bigInt = new BigInteger(bytes);
String hexString = bigInt.toString(16); // 16 is the radix

You could return hexString at this point, with the caveat that leading null-chars will be stripped, and the result will have an odd length if the first byte is less than 16. If you need to handle those cases, you can add some extra code to pad with 0s:

StringBuilder sb = new StringBuilder();
while ((sb.length() + hexString.length()) < (2 * bytes.length)) {
  sb.append("0");
}
sb.append(hexString);
return sb.toString();
user_908480

Convert a letter in hex code and hex code in letter.

        String letter = "a";
    String code;
    int decimal;

    code = Integer.toHexString(letter.charAt(0));
    decimal = Integer.parseInt(code, 16);

    System.out.println("Hex code to " + letter + " = " + code);
    System.out.println("Char to " + code + " = " + (char) decimal);
user_18310270

Using Multiple Peoples help from multiple Threads..

I know this has been answered, but i would like to give a full encode & decode method for any others in my same situation..

Here's my Encoding & Decoding methods..

// Global Charset Encoding
public static Charset encodingType = StandardCharsets.UTF_8;

// Text To Hex
public static String textToHex(String text)
{
    byte[] buf = null;
    buf = text.getBytes(encodingType);
    char[] HEX_CHARS = "0123456789abcdef".toCharArray();
    char[] chars = new char[2 * buf.length];
    for (int i = 0; i < buf.length; ++i)
    {
        chars[2 * i] = HEX_CHARS[(buf[i] & 0xF0) >>> 4];
        chars[2 * i + 1] = HEX_CHARS[buf[i] & 0x0F];
    }
    return new String(chars);
}

// Hex To Text
public static String hexToText(String hex)
{
    int l = hex.length();
    byte[] data = new byte[l / 2];
    for (int i = 0; i < l; i += 2)
    {
        data[i / 2] = (byte) ((Character.digit(hex.charAt(i), 16) << 4)
            + Character.digit(hex.charAt(i + 1), 16));
    }
    String st = new String(data, encodingType);
    return st;
}
user_61160900

One line HEX encoding/decoding without external libs (Java 8 and above):

Encoding :

String hexString = inputString.chars().mapToObj(c -> 
Integer.toHexString(c)).collect(Collectors.joining());

Decoding :

String decodedString = Stream.iterate(0, i -> i+2)
                .limit(hexString.length()/2 + Math.min(hexString.length()%2,1))
                .map(i -> "" + (char)Integer.parseInt("" + hexString.charAt(i) + hexString.charAt(i+1),16))
                .collect(Collectors.joining());
user_168400260

Java 17 introduces a utility class for hexadecimal formatting: java.util.HexFormat

Convert to hex:

public String toHex(String value) {
    return HexFormat.of().formatHex(value.getBytes());
}

Convert from hex:

public String fromHex(String value) {
    return new String(HexFormat.of().parseHex(value));
}

More about HexFormat here

Documentation: here

user_107513430

Here are some benchmarks comparing different approaches and libraries. Guava beats Apache Commons Codec at decoding. Commons Codec beats Guava at encoding. And JHex beats them both for decoding and encoding.

JHex example

String hexString = "596f752772652077656c636f6d652e";
byte[] decoded = JHex.decodeChecked(hexString);
System.out.println(new String(decoded));
String reEncoded = JHex.encode(decoded);

Everything is in a single class file for JHex. Feel free to copy paste if you don't want yet another library in your dependency tree. Also note, it is only available as Java 9 jar until I can figure out how to publish multiple release targets with Gradle and the Bintray plugin.

user_37541570

check this solution for String to hex and hex to String vise-versa

public class TestHexConversion {
public static void main(String[] args) {
    try{
        String clearText = "testString For;0181;with.love";
        System.out.println("Clear Text  = " + clearText);
        char[] chars = clearText.toCharArray();
        StringBuffer hex = new StringBuffer();
        for (int i = 0; i < chars.length; i++) {
            hex.append(Integer.toHexString((int) chars[i]));
        }
        String hexText = hex.toString();
        System.out.println("Hex Text  = " + hexText);
        String decodedText = HexToString(hexText);
        System.out.println("Decoded Text = "+decodedText);
    } catch (Exception e){
        e.printStackTrace();
    }
}

public static String HexToString(String hex){

      StringBuilder finalString = new StringBuilder();
      StringBuilder tempString = new StringBuilder();

      for( int i=0; i<hex.length()-1; i+=2 ){
          String output = hex.substring(i, (i + 2));
          int decimal = Integer.parseInt(output, 16);
          finalString.append((char)decimal);
          tempString.append(decimal);
      }
    return finalString.toString();
}

Output as follows :

Clear Text = testString For;0181;with.love

Hex Text = 74657374537472696e6720466f723b303138313b776974682e6c6f7665

Decoded Text = testString For;0181;with.love

user_99397920

A short and convenient way to convert a String to its Hexadecimal notation is:

public static void main(String... args){
String str = "Hello! This is test string.";
char ch[] = str.toCharArray();
StringBuilder sb = new StringBuilder();
    for (int i = 0; i < ch.length; i++) {
        sb.append(Integer.toHexString((int) ch[i]));
    }
    System.out.println(sb.toString());
}
user_85978100
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