IntelliJ IDEA 2019.1 Help

Analyzing Duplicates

IntelliJ IDEA helps you find repetitive blocks of code in a certain range. This range can be a single file, a project, a module, or a custom scope. Results of analysis display in the dedicated tab of the Duplicates tool window.

Search for duplicates

  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 language that you want to analyze.

    For each language, check the options to define your preferences for the analysis. 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 (to avoid reporting about each if construct in the source code).

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

    Duplicates tool window
    • View the list of duplicates in the left pane of the tool window.

    • View differences between the found duplicates in the right pane. Use the arrow buttons to place the selected duplicate in one of the sections of the differences viewer and compare fragments of the code.

    • Navigate to the duplicates in the editor, using Jump to Source or Show Source commands of the duplicates context menu.

    • Eliminate duplicates from the source code by clicking Eliminate Duplicates and specifying the method name and parameters in the Extract Method dialog. This procedure is similar to the Extract method refactoring, with the only difference that in case of duplicates analysis the repetitive blocks of code are found automatically.

Detecting duplicates on the fly

IntelliJ IDEA enables spotting duplicates on the fly. This is done by the inspection General | Duplicated code fragment.

If you stumble upon an existing duplicate, or somehow create one either by writing or pasting code, you will know it instantly. Inspection is accompanied by quick fixes, which enable you to navigate to the detected duplicates, or view all of them in the Find tool window:

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Last modified: 20 May 2019

See Also