apache/druid · error · NumberFormatException

Cannot parse string to double

Error message

Cannot parse string to double

What it means

Numbers.parseDoubleObject(String) parses a String to a boxed Double using Guava's Doubles.tryParse. If the string cannot be parsed as a double, it throws NumberFormatException "Cannot parse string to double". It is the strict (exploding) counterpart of tryParseDouble.

Solutions

1. Validate/trim and normalize the string (strip units, commas, whitespace) before parsing.
2. Use the lenient Numbers.tryParseDouble(s, nullValue) or Doubles.tryParse(s) and handle null instead of throwing.
3. Catch NumberFormatException and treat the value as null/NaN.
4. Fix the data source so the field is genuinely numeric.

Example fix

// before
Double d = Numbers.parseDoubleObject(str);
// after
Double d = Doubles.tryParse(str == null ? null : str.trim());
if (d == null) { d = 0.0; /* or skip row */ }

Double d = (str == null) ? null : Doubles.tryParse(str.trim());
if (d == null) { throw new IllegalArgumentException("Not a double: " + str); }

boolean isDoubleString(String s) { return s != null && Doubles.tryParse(s.trim()) != null; }

Double d;
try { d = Numbers.parseDoubleObject(s); } catch (NumberFormatException e) { LOG.warn("Unparseable double: %s", s); d = null; }

When it happens

Trigger: Calling Numbers.parseDoubleObject(s) with a non-numeric or malformed string such as "abc", "1,000" (comma groupings), an empty string, or a string with currency symbols.

Common situations: Parsing CSV/config/JSON string fields that are expected numeric but contain blanks, locale-formatted numbers, or stray whitespace/units (e.g. "10ms").

Understand the failure class

Background: "Invalid ... format", "must be in format X", "does not look like a ..." — invalid argument format errors across CLI tools and libraries — this error's family across 17 libraries.

Related errors

• Cannot parse string to long
• Failed to parse array element
• Invalid format or out of range of long
• Key[ ] should be a long, was[ ]
• Key[ ] should be an int, was[ ]

AI-assisted analysis of apache/druid@9b90983fd2 (2026-09-07). Data as JSON: /api/errors/b220f63ccf5d2f7a. Report an issue: GitHub.

Appendix: source

Thrown at processing/src/main/java/org/apache/druid/java/util/common/Numbers.java:185

      throw new IAE("Unknown object type [%s]", val.getClass().getName());
    }
  }

  /**
   * Like {@link #tryParseDouble}, but does not produce a primitive and will explode if unable to produce a Double
   * similar to {@link Double#parseDouble}
   */
  @Nullable
  public static Double parseDoubleObject(@Nullable String val)
  {
    if (val == null) {
      return null;
    }
    Double d = Doubles.tryParse(val);
    if (d != null) {
      return d;
    }
    throw new NumberFormatException("Cannot parse string to double");
  }

  /**
   * Like {@link #tryParseLong} but does not produce a primitive and will explode if unable to produce a Long
   * similar to {@link Long#parseLong}
   */
  @Nullable
  public static Long parseLongObject(@Nullable String val)
  {
    if (val == null) {
      return null;
    }
    Long lobj = Longs.tryParse(val);
    if (lobj != null) {
      return lobj;
    }
    // try as a double, for "ddd.dd" , Longs.tryParse(..) returns null
    Double dobj = Doubles.tryParse(val);

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