Code reference information

Last modified: 15 June 2021

Definitions

In IntelliJ IDEA, you can see where and how symbols, such as tags, classes, fields, methods, or functions are defined in your project. For this purpose, the IDE features the Quick Definition popup.

  • To view definition of a symbol, select it in the editor and press Ctrl+Shift+I (or click View | Quick Definition ).

Quick Definition popup

Alternatively, with the Ctrl key pressed, hover the cursor over any symbol. IntelliJ IDEA displays the symbol as a link and shows its definition in a tooltip. Click this link to jump to the definition of the symbol.

https://resources.jetbrains.com.cn/help/img/idea/2021.1/view-definition.png
Gif

You can open a definition in the Find tool window. To do so, click the Options icon in the top-right corner of the popup and click Open in Find tool window Open in Find Tool Window.

To open the source code of the definition for editing and close the popup, click the Options icon and then click Edit Edit Source (F4 ).

tip

For markup languages, IntelliJ IDEA retrieves definitions of symbols from the specified DTD or schema. For details, see HTML and XML.

Type definitions

The Quick Type Definition feature allows you to view the type definition of variables, fields, methods, or any other symbols in a popup without switching from the code you're editing.

  • Place the caret at the symbol for which you want to view the type definition and select View | Quick Type Definition.

    Viewing type definition in a popup

    To open the source code of the definition for editing and close the popup, click the Options icon and then click Edit Edit Source (F4 ).

IntelliJ IDEA doesn't have a default keyboard shortcut for this action, but you can manually configure it in the settings. For more information on how to configure custom shortcuts, refer to Configure keyboard shortcuts.

Parameter info

The Parameter Info popup shows the names of parameters in method and function calls. IntelliJ IDEA automatically shows a popup with all available method signatures within 1 second (1000 milliseconds) after you type an opening bracket in the editor, or select a method from the suggestions list.

You can explicitly invoke the popup if it has closed or if your IDE is configured not to show the popup automatically. To do so, press Ctrl+P (or click View | Parameter Info ).

https://resources.jetbrains.com.cn/help/img/idea/2021.1/parameter-info.png
Gif

Show full method or function signatures

By default, the parameter info popup shows simple signatures. You can configure the IDE to show full signatures that include method names and returned types.

  • In the Settings/Preferences dialog Ctrl+Alt+S, go to Editor | General | Code Completion, and select the Show full method signatures checkbox.

    Full signatures enabled

Configure the parameter info popup

  1. In the Settings/Preferences dialog Ctrl+Alt+S, go to Editor | General | Code Completion.

  2. In the Show the parameter info popup in ... milliseconds field, specify the time in milliseconds after which the popup should appear.

If you don't want the popup to appear automatically, clear the Show the parameter info popup in ... milliseconds checkbox.

Inlay hints

Inlay hints are special markers that appear in the editor and provide you with additional information about your code, like the names of the parameters that a called method expects. Other types of hints inform you about annotations, method parameters, usages, and so on (depending on the language).

Parameter hints

Some of the hints are enabled by default.

You can fine-tune inlay hints in Settings/Preferences | Editor | Inlay Hints. For detailed explanation of what each type does, see Inlay Hints.

Configure the parameter hints exception list

If you don't want to see parameter hints for specific methods, you can configure the list with exceptions. By default, the exception list contains a number of pre-defined methods. You can remove a method from the list to see the hints for it, or add new methods to hide their hints in the editor.

  1. In the Settings/Preferences dialog Ctrl+Alt+S, select Editor | Inlay Hints and click the necessary language.

  2. Select Parameter hints in the list in the middle section.

    The options for configuring hints become available on the right.

  3. Add methods for which you don't want to see the hints to the Exclude list section.

  4. Add cases for which you do not want to see the hints to the Exclude list section. To add a case, click the inline hint in your code, press Alt+Enter and select Do not show hints for current method.

  5. Apply the changes and close the dialog.

Quick documentation

You can get quick information for any symbol or method signature by means of the Quick Documentation popup. Note that the symbol must be supplied with documentation comments created in accordance with the Javadoc markup or with the SDK documentation.

The popup allows you to access both downloaded documentation and external documentation for which you only specify its URL. For information on how to add code documentation to be able to open in the popup, refer to:

View quick documentation

  • Hover the mouse over the necessary symbol to view its documentation, or place the caret at the symbol, and press Ctrl+Q (View | Quick Documentation ).

    Press Ctrl+Q again to switch between the popup and the toolbar.

    Quick Documentation popup

Click the Show Options Menu icon in the popup to change the font size, display the quick documentation toolbar, or go to the source code.

Disable quick documentation on hover

  • In the Settings/Preferences dialog Ctrl+Alt+S, go to Editor | Code Editing | Quick Documentation and clear the Show quick documentation on mouse move checkbox.

    You can also click the Show Options Menu icon in the popup and disable the Show on Mouse Move option.

In this case, to view documentation for a symbol at caret, press Ctrl+Q or select View | Quick Documentation from the main menu.

tip

To specify the delay in milliseconds after which the popup should appear, In the Settings/Preferences dialog Ctrl+Alt+S, go to Editor | Code Editing | Editor Tooltips and enter the necessary value in the Tooltip delay field.

External documentation

External documentation opens the necessary information in a web browser so that you can navigate to related symbols and keep the information for further reference at the same time. After you configure external documentation for your project, you can also view it in the Quick Documentation popup.

For information on how to configure library and SDK external documentation paths, refer to:

View external documentation

  • To view documentation for a symbol at the caret in a browser, press Shift+F1 or select View | External Documentation from the main menu.

Type Info

In IntelliJ IDEA, you can identify the type of an expression in the following way:

  • Place the caret at the necessary code element and press Ctrl+Shift+P (or select View | Type Info from the main menu).

    If several expressions are available, select the desired one from the popup menu and press Enter.

    Showing the expression type info

Expression static data

IntelliJ IDEA allows you to view statically known information about any Java expression in the editor. This information helps you understand complex code with heavy branching and elaborates the expression type information.

  • To view static information on Java expressions, place the caret at the expression and double-press Ctrl+Shift+P.

https://resources.jetbrains.com.cn/help/img/idea/2021.1/expression-static-data.png
Gif

In this example, the Expression static data action shows that the type of list is actually ArrayList, despite the variable is declared as List, and it's still empty at the given point (size = 0).

Productivity tips

Copy tooltip text to the clipboard

To copy tooltip text to the clipboard, hold Alt (on Linux, hold Ctrl+Alt) and click the tooltip.

View context information

If the current method or class declaration is not visible, you can view it in the tooltip by pressing Alt+Q.

See also

Getting Started