IntelliJ IDEA 2019.2 Help

Inspection: Duplicated code fragment

IntelliJ IDEA helps you find repetitive blocks of code in a certain set of files by means of the Duplicated code fragment inspection. If you create a duplicate by writing or pasting code, IntelliJ IDEA highlights it right away and suggests quick-fixes.

The inspection works out of the box and has a number of settings that you can change to adjust its behavior.

Configure the inspection

  1. In the Settings/Preferences dialog (Ctrl+Alt+S), go to Editor | Inspections.

  2. Make sure that the necessary inspection profile is selected in the Profile list.

  3. In the search field of the Inspections dialog, type duplicated code fragment to locate the inspection in the list.

    Once you click the inspection, its settings appear on the right.

    • Severity: select a severity level from the list or create a new one.

    • Scope: select the scope of files in which the inspection is going to operate (the code on which the inspection in going to run).

    • Show duplicates from: select the set of files from which duplicates are going to be shown.

      You can restrict the analysis to see duplicates only from the same module or from the same file to avoid false-positive results.

    • Skip duplicates simpler than: configure the size of the code fragment that is compared against the rest of the code in the selected set of files in units.

      The default value is a compromise between accuracy and the amount of found duplicates. Increase the value to get more accurate results. Decrease the value to find more duplicates.

      The exact value of units can be calculated as follows: units = 2 * number of statements + number of expressions.

    • Select the languages for which this inspection is going to work.

  4. Apply the changes and close the dialog.

Configuring the inspection

Anonymize constructs

You can configure the constructs that you want to anonymize for each file type. This means that you can define whether two identical entities that use different names or values should be treated as duplicates.

  1. Click the link in the inspection description, or in the Settings/Preferences dialog (Ctrl+Alt+S), select Editor | Duplicates.

  2. Select the file types to which the analysis should apply and select the checkboxes next to the constructs that you want to anonymize.

  3. Apply the changes and close the dialog.

The dialog also allows you to completely exclude the languages from the analysis and indexing. If you disable a language on this page, this language will be hidden in the inspection settings.

Anonymize constructs

Manually search for duplicates (deprecated)

  1. From the main menu, select Analyze | Locate Duplicates.

  2. In the Specify Code Duplication Analysis Scope dialog, specify the analysis scope: whole project, current file, uncommitted files (for the projects under version control), or some custom scope. In addition, you can include test sources into the analysis, too.

  3. In the Code Duplication Analysis Settings dialog, select the languages that you want to analyze.

    For each language, check the options to define the analysis preferences. For example, you can opt to request identical match for code fragments to be considered duplicates, or specify a certain limit below which the code constructs are not considered duplicates (for example, to avoid reporting each if construct in the source code).

  4. In the Duplicates tool window, explore the analysis results.

    Duplicates tool window
Last modified: 23 August 2019

See Also