1. All Inspections
  2. RegExp
  3. Duplicate character in character class

Duplicate character in character class

Last modified: Last modified: 18 September 2025

Reports duplicate characters inside a RegExp character class. Duplicate characters are unnecessary and can be removed without changing the semantics of the regex.

Example:

After the quick-fix is applied:

Locating this inspection

By ID

Can be used to locate inspection in e.g. Qodana configuration files, where you can quickly enable or disable it, or adjust its settings.

RegExpDuplicateCharacterInClass
Via Settings dialog

Path to the inspection settings via IntelliJ Platform IDE Settings dialog, when you need to adjust inspection settings directly from your IDE.

Settings or Preferences | Editor | Inspections | RegExp

Inspection ID: RegExpDuplicateCharacterInClass

Suppressing Inspection

You can suppress this inspection by placing the following comment marker before the code fragment where you no longer want messages from this inspection to appear:

note

Actual comment syntax will depend on the code language you are working with

More detailed instructions as well as other ways and options that you have can be found in the product documentation:

Inspection Details

By default bundled with:

CLion 2025.2, DataGrip 2025.2, DataSpell 2025.2, GoLand 2025.2, IntelliJ IDEA 2025.2, JetBrains Rider 2025.2, PhpStorm 2025.2, PyCharm 2025.2, Qodana for .NET 2025.2, Qodana for Go 2025.2, Qodana for JS 2025.2, Qodana for JVM 2025.2, Qodana for PHP 2025.2, Qodana for Ruby 2025.2, RubyMine 2025.2, WebStorm 2025.2