Convert Hex to ASCII in Java

Table of Contents

1. Overview
2. ASCII to Hex
3. Hex to ASCII Format
4. Test
5. Conclusion

1. Overview

In this quick article, we’re going to do some simple conversions between the Hex and ASCII formats.

In a typical use case, the Hex format can be used to write down very large integer values in a compact form. For example, AD45 is shorter than its decimal equivalent 44357 and as values increase the difference in length becomes even more pronounced.

2. ASCII to Hex

Now, let’s look at our options to convert ASCII values to Hex:

Convert String to char array
Cast each char to an int
Use Integer.toHexString() to convert it to Hex

Here’s a quick example how we can achieve above steps:

private static String asciiToHex(String asciiStr) {
    char[] chars = asciiStr.toCharArray();
    StringBuilder hex = new StringBuilder();
    for (char ch : chars) {
        hex.append(Integer.toHexString((int) ch));
    }

    return hex.toString();
}

3. Hex to ASCII Format

Similarly, let’s do a Hex to ASCII format conversion in three steps :

Cut the Hex value in 2 char groups
Convert it to base 16 Integer using Integer.parseInt(hex, 16) and cast to char
Append all chars in a StringBuilder

Let’s look at an example how we can achieve above steps:

private static String hexToAscii(String hexStr) {
    StringBuilder output = new StringBuilder("");
    
    for (int i = 0; i < hexStr.length(); i += 2) {
        String str = hexStr.substring(i, i + 2);
        output.append((char) Integer.parseInt(str, 16));
    }
    
    return output.toString();
}

4. Test

Finally, using these methods, let’s do a quick test :

@Test
public static void whenHexToAscii() {
    String asciiString = "www.maixuanviet.com";
    String hexEquivalent = 
      "7777772e6261656c64756e672e636f6d";

    assertEquals(asciiString, hexToAscii(hexEquivalent));
}

@Test
public static void whenAsciiToHex() {
    String asciiString = "www.maixuanviet.com";
    String hexEquivalent = 
      "7777772e6261656c64756e672e636f6d";

    assertEquals(hexEquivalent, asciiToHex(asciiString));
}