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Call to 'String.toUpperCase()' or 'toLowerCase()' without locale

Reports toUpperCase() or toLowerCase() calls on String objects that do not specify a java.util.Locale. In these cases the default system locale is used, which can cause problems in an internationalized environment.

For example the code "i".toUpperCase().equals("I") returns false in the Turkish and Azerbaijani locales, where the dotted and dotless 'i' are separate letters. Calling toUpperCase() on an English string containing an 'i', when running in a Turkish locale, will return incorrect results. Alternatively, when dealing with strings that should be treated as locale-independent, like HTML tags, this can lead to errors.

Locating this inspection

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

StringToUpperCaseOrToLowerCaseWithoutLocale
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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 | Java | Internationalization

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:

//noinspection StringToUpperCaseOrToLowerCaseWithoutLocale

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:

IntelliJ IDEA 2025.2, Qodana for JVM 2025.2,

Last modified: 18 September 2025