apache/hadoop · error · IllegalArgumentException

bytes == null

Error message

bytes == null

What it means

StringUtils.byteToHexString(byte[], int, int) renders a byte range as hex and enforces a null precondition: a null array throws IllegalArgumentException('bytes == null') before any iteration. The caller handed it an absent value — typically a digest or buffer that a producer returned as null on failure.

Source

Thrown at hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/StringUtils.java:185

    sbuf.append(strs[0]);
    for (int idx = 1; idx < strs.length; idx++) {
      sbuf.append(",");
      sbuf.append(strs[idx]);
    }
    return sbuf.toString();
  }

  /**
   * Given an array of bytes it will convert the bytes to a hex string
   * representation of the bytes
   * @param bytes bytes.
   * @param start start index, inclusively
   * @param end end index, exclusively
   * @return hex string representation of the byte array
   */
  public static String byteToHexString(byte[] bytes, int start, int end) {
    if (bytes == null) {
      throw new IllegalArgumentException("bytes == null");
    }
    StringBuilder s = new StringBuilder(); 
    for(int i = start; i < end; i++) {
      s.append(format("%02x", bytes[i]));
    }
    return s.toString();
  }

  /**
   * Same as byteToHexString(bytes, 0, bytes.length).
   * @param bytes bytes.
   * @return byteToHexString.
   */
  public static String byteToHexString(byte bytes[]) {
    return byteToHexString(bytes, 0, bytes.length);
  }

  /**

View on GitHub (pinned to 2add963021)

Solutions

1. Null-check at the boundary: if (bytes != null) hex = StringUtils.byteToHexString(bytes, 0, bytes.length);
2. Fix the producer to return an empty array (or throw) instead of null on failure
3. Use Objects.requireNonNull(bytes, "bytes") earlier to fail with your own clearer message
4. Prefer byteToHexString(bytes, 0, bytes.length) only after length is validated for the start/end range

Example fix

// before
String hex = StringUtils.byteToHexString(digest, 0, digest.length); // digest null on hash failure

// after
byte[] digest = md != null ? md.digest() : new byte[0];
String hex = StringUtils.byteToHexString(digest, 0, digest.length);

if (bytes == null) {
  throw new IllegalArgumentException("bytes required for hex conversion");
}
String hex = StringUtils.byteToHexString(bytes, 0, bytes.length);

When it happens

Trigger: Passing a null byte[] — e.g. messageDigest.digest() result stored without error handling, an uninitialized field, or a map.get(key) miss whose null flows into logging/hex conversion.

Common situations: Checksum/hash helpers that return null on exception; optional binary attributes absent from a metadata map; defensive-logging code that itself NPEs on null input.

Related errors

• null param while calling Method: [{}]
• null param while calling Method: [{}]
• Null protocol
• Path must be absolute: " + path
• Rename dir to self is forbidden

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/410a8350d69cba01. Report an issue: GitHub.