apache/flink · error · NumberFormatException

Empty field.

Error message

Empty field.

What it means

Thrown by ByteParser.parseField(byte[], int, int, char) when the first byte of the field equals the delimiter, meaning the column is empty. The parser scans bytes directly and treats a delimiter at the start position as an empty field, rejecting it with NumberFormatException before any digit processing.

Source

Thrown at flink-core/src/main/java/org/apache/flink/types/parser/ByteParser.java:121

    /**
     * Static utility to parse a field of type byte from a byte sequence that represents text
     * characters (such as when read from a file stream).
     *
     * @param bytes The bytes containing the text data that should be parsed.
     * @param startPos The offset to start the parsing.
     * @param length The length of the byte sequence (counting from the offset).
     * @param delimiter The delimiter that terminates the field.
     * @return The parsed value.
     * @throws NumberFormatException Thrown when the value cannot be parsed because the text
     *     represents not a correct number.
     */
    public static final byte parseField(byte[] bytes, int startPos, int length, char delimiter) {
        long val = 0;
        boolean neg = false;

        if (bytes[startPos] == delimiter) {
            throw new NumberFormatException("Empty field.");
        }

        if (bytes[startPos] == '-') {
            neg = true;
            startPos++;
            length--;
            if (length == 0 || bytes[startPos] == delimiter) {
                throw new NumberFormatException("Orphaned minus sign.");
            }
        }

        for (; length > 0; startPos++, length--) {
            if (bytes[startPos] == delimiter) {
                return (byte) (neg ? -val : val);
            }
            if (bytes[startPos] < 48 || bytes[startPos] > 57) {
                throw new NumberFormatException("Invalid character.");
            }

View on GitHub (pinned to 2f3c205e92)

Solutions

1. Fix the input data or delimiter config so byte columns are non-empty.
2. Guard at the call site: if bytes[startPos] == delimiter, substitute a default or skip the record.
3. If empty cells are valid in your format, define an explicit mapping (empty -> 0/null) instead of parsing.

Example fix

// before
byte v = ByteParser.parseField(bytes, start, len, '|');

// after
byte v = (len > 0 && bytes[start] == (byte) '|')
    ? 0
    : ByteParser.parseField(bytes, start, len, '|');

if (len <= 0 || bytes[start] == (byte) delimiter) {
    // empty column: default or explicit error
    return 0;
}

try {
    byte v = ByteParser.parseField(bytes, start, len, delim);
} catch (NumberFormatException e) {
    // empty or malformed field: emit to side output with row context
}

When it happens

Trigger: Calling ByteParser.parseField(bytes, startPos, length, delimiter) where bytes[startPos] == (byte) delimiter — e.g. input "a||c" parsed with '|' delimiter hitting an empty middle column.

Common situations: CSV with consecutive delimiters (empty numeric cell), trailing delimiter on a line producing an empty last field, or a column-count mismatch after a schema change drops a column.

Related errors

• Invalid input: Empty string
• Orphaned minus sign.
• Invalid character.
• Value overflow/underflow
• Empty field.

AI-assisted analysis of apache/flink@2f3c205e92 (2026-08-14). Data as JSON: /api/errors/cfdba18f428ec86b. Report an issue: GitHub.