CodeQL documentation

Unused format argument

ID: java/unused-format-argument
Kind: problem
Severity: warning
Precision: very-high
Tags:
   - maintainability
   - useless-code
   - external/cwe/cwe-685
Query suites:
   - java-security-and-quality.qls

Click to see the query in the CodeQL repository

When formatting strings using printf-style format strings, one must ensure that the number of supplied arguments matches the number of arguments referenced by the format string. Additional arguments will be thrown away silently, which may not be the intended behavior, and too few arguments will cause an IllegalFormatException.

Format strings are used by the format method on the classes String, Formatter, Console, PrintWriter, and PrintStream. Several of these classes also supply the method alias printf. The class Console has two additional methods, readLine and readPassword, that also use format strings.

Recommendation

Change the format string to use all the arguments, or remove the unnecessary arguments.

Example

The following example supplies three arguments to be formatted, but the format string only refers to two arguments, so this will silently ignore the third argument.

System.out.format("First string: %s Second string: %s", "Hello", "world", "!");

References