Infer nullity
The nullability analysis in IntelliJ IDEA can scan your code and add @Nullable and @NotNull annotations to your code. The analysis helps you detect contract violations in your code and suggests null checks where possible.
Run the nullability analysis
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From the main menu, select .
If you haven't added the library with annotations to the classpath, IntelliJ IDEA will prompt you to download it from Maven.
In the Specify Infer Nullity Scope dialog, select the scope of the analysis. If you want to include test sources and annotate local variables, select the corresponding checkboxes.
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Click OK.
IntelliJ IDEA adds import statements for annotations if required, and annotates parameters and variables.
Inferred annotations
IntelliJ IDEA scans bytecode from SDKs and libraries and infers the @Nullable and @NotNull annotations automatically. You can use these annotations later to analyze your source code to spot places where you overlooked null.
In the editor, inferred annotations are marked with the 
gutter icon.
Show inferred annotations inline
You can configure the IDE to show inferred annotations right in your code.
Press Ctrl+Alt+S to open the Settings/Preferences dialog and go to .
Select the Show inferred annotations inline checkbox.
Apply the changes and close the dialog.
