Package org.bluezoo.util

Class ByteArrays

java.lang.Object
org.bluezoo.util.ByteArrays
public final class ByteArrays extends Object
Utility methods for byte array operations.

This class provides efficient implementations for common byte array operations including hexadecimal encoding/decoding and comparison.

Hexadecimal Conversion

The toHexString(byte[]) and toByteArray(String) methods provide efficient conversion between byte arrays and hexadecimal strings. These are optimized for performance, avoiding the overhead of String.format() or Integer.toHexString().

Usage Examples


 // Convert MD5 hash to hex string
 MessageDigest md = MessageDigest.getInstance("MD5");
 md.update(data);
 String hashHex = ByteArrays.toHexString(md.digest());
 
 // Parse hex string back to bytes
 byte[] bytes = ByteArrays.toByteArray("48656c6c6f");
 
 // Constant-time comparison for security-sensitive contexts
 boolean match = ByteArrays.equals(computed, expected);

Thread Safety

All methods in this class are stateless and thread-safe.

Author:
Chris Burdess

  • Method Details

    • toByteArray

      public static byte[] toByteArray(String hexString)
      Decodes a hexadecimal string into a byte array.

      Each pair of hexadecimal characters is converted to a single byte. Both uppercase and lowercase hex digits are accepted.

      Parameters:
      hexString - the hexadecimal string to decode (must have even length)
      Returns:
      the decoded byte array
      Throws:
      IllegalArgumentException - if the string is null, has odd length, or contains non-hexadecimal characters

    • toHexString

      public static String toHexString(byte[] byteArray)
      Encodes a byte array as a lowercase hexadecimal string.

      This implementation is optimized for performance, using direct character array manipulation rather than String.format() or StringBuilder.append().

      The output uses lowercase hexadecimal digits (0-9, a-f).

      Parameters:
      byteArray - the byte array to encode
      Returns:
      the hexadecimal string representation
      Throws:
      IllegalArgumentException - if the byte array is null

    • equals

      public static boolean equals(byte[] b1, byte[] b2)
      Compares two byte arrays for equality.

      This method returns false as soon as a mismatch is found, making it efficient for general-purpose comparison. For security-sensitive comparisons where timing attacks are a concern (e.g., comparing MACs), use equalsConstantTime(byte[], byte[]) instead.

      Parameters:
      b1 - the first byte array
      b2 - the second byte array
      Returns:
      true if both arrays are non-null, have the same length, and contain identical bytes; false otherwise

    • equalsConstantTime

      public static boolean equalsConstantTime(byte[] b1, byte[] b2)
      Compares two byte arrays for equality in constant time.

      This method always iterates through all bytes of equal-length arrays, preventing timing attacks that could reveal information about the position of mismatched bytes. Use this for security-sensitive comparisons such as MAC verification or password hash comparison.

      Returns false immediately if either array is null or if the arrays have different lengths (length comparison is not constant-time as it is typically not security-sensitive).

      Parameters:
      b1 - the first byte array
      b2 - the second byte array
      Returns:
      true if both arrays are non-null, have the same length, and contain identical bytes; false otherwise