apache/hadoop · error · IllegalArgumentException

name + " cannot be negative but was: " + value

Error message

name + " cannot be negative but was: " + value

What it means

org.apache.hadoop.util.Lists is Hadoop's internal near-copy of Guava's Lists. Before sizing a backing array via computeArrayListCapacity (saturatedCast of 5L + arraySize + arraySize/10), checkNonnegative rejects a negative arraySize with IllegalArgumentException("arraySize cannot be negative but was: N"). Zero is legal; only negatives throw.

Source

Thrown at hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/Lists.java:199

   * @param elements elements.
   * @param <E> Generics Type E.
   * @return Generics Type E List.
   */
  public static <E> LinkedList<E> newLinkedList(
      Iterable<? extends E> elements) {
    LinkedList<E> list = newLinkedList();
    addAll(list, elements);
    return list;
  }

  private static int computeArrayListCapacity(int arraySize) {
    checkNonnegative(arraySize, "arraySize");
    return saturatedCast(5L + arraySize + (arraySize / 10));
  }

  private static int checkNonnegative(int value, String name) {
    if (value < 0) {
      throw new IllegalArgumentException(name + " cannot be negative but was: "
          + value);
    }
    return value;
  }

  /**
   * Returns the {@code int} nearest in value to {@code value}.
   *
   * @param value any {@code long} value.
   * @return the same value cast to {@code int} if it is in the range of the
   *     {@code int} type, {@link Integer#MAX_VALUE} if it is too large,
   *     or {@link Integer#MIN_VALUE} if it is too small.
   */
  private static int saturatedCast(long value) {
    if (value > Integer.MAX_VALUE) {
      return Integer.MAX_VALUE;
    }
    if (value < Integer.MIN_VALUE) {

View on GitHub (pinned to 2add963021)

Solutions

1. Clamp the estimate before the call: Math.max(0, n)
2. Use newArrayListWithExpectedSize or plain newArrayList() when the capacity is unknown
3. Fix the upstream expression that can go negative and add a unit test for the empty-input case

Example fix

// before
List<String> l = Lists.newArrayListWithCapacity(expected - RESERVE);

// after
List<String> l = Lists.newArrayListWithCapacity(Math.max(0, expected - RESERVE));

int size = Math.max(0, computeEstimate(...));
List<String> list = size > 0 ? Lists.newArrayListWithCapacity(size) : Lists.<String>newArrayList();

When it happens

Trigger: Lists.newArrayListWithCapacity(n) with n < 0 — typically n from an estimate that underflowed (expectedSize - reserved, size/2 - x) or a config-parsed capacity with a negative 'unset' sentinel.

Common situations: Copied Guava idioms resolving to Hadoop's Lists; expected-size arithmetic on empty or tiny inputs; forwarding a -1 default from an unset configuration key.

Related errors

• Illegal option {}
• Not enough arguments: expected {} but got {}
• Too many arguments: expected {} but got {}
• Target path not specified. <target path> <src path> <src pat
• The number of source paths is less than 2. <target path> <sr

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/4c31305907e1daa9. Report an issue: GitHub.