Introduction:

Hexadecimal representation is commonly used in computing for various purposes, such as encoding binary data and presenting cryptographic keys. In Java, converting a regular string to a hex string can be achieved in different ways, depending on the desired format of the output. In this blog, we will explore several methods to convert a string to a hexadecimal string in a specific format using Java. 

Method 1: Using StringBuilder and Integer.toHexString()

The first approach to converting a string to a hex string in a specific format is by utilizing the StringBuilder class and the Integer.toHexString() method. This method will convert each character in the string to its corresponding hexadecimal representation.

// Java program to convert a string to a specific format of hexadecimal string
public class HexStringConverter {

    // Method 1: Using StringBuilder and Integer.toHexString()
    public static String convertToHexMethod1(String input) {
        StringBuilder hexString = new StringBuilder();

        for (char c : input.toCharArray()) {
            String hex = Integer.toHexString(c);
            hexString.append(hex);
        }

        return hexString.toString();
    }

    public static void main(String[] args) {
        String inputString = "Hello, World!";
        String hexOutputMethod1 = convertToHexMethod1(inputString);
        System.out.println("Method 1 Output: " + hexOutputMethod1);
    }
}

Output:

Method 1 Output: 48656c6c6f2c20576f726c6421

In this method, we iterate through each character in the input string and convert it to its hexadecimal representation using Integer.toHexString(). The result is then appended to the StringBuilder object. Finally, we return the StringBuilder as a string, containing the hexadecimal representation of the original string.

Method 2: Using String.format()

The second approach involves using the String.format() method to format the hexadecimal output. This method provides a more convenient way to control the format of the resulting hex string.

// Method 2: Using String.format()
public static String convertToHexMethod2(String input) {
    StringBuilder hexString = new StringBuilder();

    for (char c : input.toCharArray()) {
        String hex = String.format("%02x", (int) c);
        hexString.append(hex);
    }

    return hexString.toString();
}

Output:

Method 2 Output: 48656c6c6f2c20576f726c6421

In this method, we utilize the String.format() method with the format specifier %02x. The %02 part means that the output will be at least two characters wide, padded with leading zeros if necessary. The x represents the conversion to hexadecimal. This ensures that each character is converted to a two-digit hexadecimal representation.

Method 3: Using Apache Commons Codec Library

The third approach utilizes the Apache Commons Codec library, which provides utility classes for encoding and decoding data in various formats, including hexadecimal.

import org.apache.commons.codec.binary.Hex;

// Method 3: Using Apache Commons Codec Library
public static String convertToHexMethod3(String input) {
    byte[] bytes = input.getBytes();
    return Hex.encodeHexString(bytes);
}

Output:

Method 3 Output: 48656c6c6f2c20576f726c6421

In this method, we convert the input string to an array of bytes using getBytes(). Then, we use the Hex.encodeHexString() method from the Apache Commons Codec library to directly obtain the hexadecimal representation of the byte array. This method saves us from manually converting each character to hexadecimal.

Conclusion:

In this blog, we explored three different methods to convert a string to a hexadecimal string in a specific format using Java. The first method used StringBuilder and Integer.toHexString(), the second method utilized String.format(), and the third method leveraged the Apache Commons Codec library.