NumberFormatException ☕ Java

java.lang.NumberFormatException: For input string: "x"

A string couldn’t be parsed as a number — it’s empty, has spaces/commas, is too large, or isn’t numeric.

Seen on: Java Android

Meaning

Integer.parseInt, Long.parseLong and Double.parseDouble are strict. The message shows the exact input in quotes — look for empty strings, whitespace, thousands separators, decimals passed to parseInt, or values beyond Integer.MAX_VALUE.

Common causes

  • Empty or null-ish string ("", "null")
  • Whitespace or newline (" 42\n")
  • Thousands separators/currency ("1,200", "₹500")
  • Decimal to parseInt ("3.5")
  • Overflow ("3000000000" for int)

⚡ Quick fix

  1. Trim and validate before parsing
  2. Use Long or BigDecimal for big/decimal values
  3. Use NumberFormat for locale-formatted numbers
  4. Catch the exception and return a validation error

Detailed fix by platform

Java

  1. Defensive parsing:
    java
    static Optional<Integer> parseIntSafe(String s) {
    if (s == null || s.isBlank()) return Optional.empty();
    try { return Optional.of(Integer.parseInt(s.trim())); }
    catch (NumberFormatException e) { return Optional.empty(); }
}

How to diagnose

  1. Input — What string is in quotes?
  2. Type — Does it fit int / need decimals?
  3. Source — Form, CSV, env var?

🧠 Still stuck? Analyze your error

Paste the full message, response headers or stack trace — we'll detect the platform and point to the most likely cause.