How can you convert a byte array to a hexadecimal string and vice versa?

 

You can convert a byte array to a hexadecimal string and vice versa in Java using the Hex class from the org.apache.commons.codec.binary package, which is part of the Apache Commons Codec library. Here's how you can do it:

1. Convert Byte Array to Hexadecimal String:

java

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

public class ByteArrayToHexExample {

    public static void main(String[] args) {
        byte[] byteArray = {0x48, 0x65, 0x6C, 0x6C, 0x6F}; // "Hello" in ASCII
        
        String hexString = Hex.encodeHexString(byteArray);
        System.out.println("Hexadecimal String: " + hexString);
    }
}

In this example, the Hex.encodeHexString method converts the byte array to a hexadecimal string representation.

2. Convert Hexadecimal String to Byte Array:

java

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

public class HexToByteArrayExample {

    public static void main(String[] args) {
        String hexString = "48656C6C6F"; // "Hello" in hexadecimal
        
        try {
            byte[] byteArray = Hex.decodeHex(hexString);
            System.out.println("Byte Array: " + byteArrayToString(byteArray));
        } catch (DecoderException e) {
            System.err.println("Invalid hexadecimal string");
        }
    }

    public static String byteArrayToString(byte[] byteArray) {
        StringBuilder sb = new StringBuilder();
        for (byte b : byteArray) {
            sb.append((char) b);
        }
        return sb.toString();
    }
}

In this example, the Hex.decodeHex method converts the hexadecimal string back to a byte array. We also define the byteArrayToString method to convert the byte array to a readable string.

To use the Apache Commons Codec library, you need to add it to your project's dependencies. If you're using a build tool like Maven or Gradle, you can include the library as a dependency in your project's configuration file.

Please note that while the example above uses the Apache Commons Codec library, you can also achieve similar functionality using built-in Java classes like ByteBuffer and String. However, using a library like Apache Commons Codec can simplify the process and handle edge cases more gracefully.