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Code reference information

Last modified: 27 February 2025

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 suggestion 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 Ctrl0P (or click View | Parameter Info).

Parameter info popup

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 dialog (CtrlAlt0S) , 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 dialog (CtrlAlt0S) , 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.

Quick Documentation

You can get quick information for any symbol right from the editor with the Quick Documentation feature. It shows you code documentation in a popup as you hover over code elements. Note that the symbol must be supplied with documentation comments created in accordance with the Javadoc markup or with the SDK documentation.

The feature allows you to access both downloaded documentation and external documentation for which you only specify its URL. For more information about adding code documentation, refer to:

Quick Documentation in a popup

View Quick Documentation in a popup

  • Hover over the necessary symbol in the editor.

  • Place the caret at the symbol and press Ctrl0Q (View | Quick Documentation).

    Press Ctrl0Q again to open this documentation in the Documentation tool window.

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.

tip

To specify the delay after which the popup should appear, in the Settings dialog (CtrlAlt0S) , go to Editor | Code Editing | Editor Tooltips and enter the necessary value in the Tooltip delay field.

When you’re viewing documentation for a library or dependency, you can access its sources right from the popup or tool window by clicking Download documentation.

Downloading documentation from popup

Disable Quick Documentation on hover

By default, the quick documentation popup appears as you hover over code elements. You can configure the IDE to display the popup only after you explicitly invoke the Quick Documentation feature.

  • Click the Show Options Menu icon in the popup and disable the Show on Mouse Move option.

  • In the Settings dialog (CtrlAlt0S) , go to Editor | Code Editing | Quick Documentation and clear the Show quick documentation on hover checkbox.

    In this case, to view documentation for a symbol at caret, press Ctrl0Q or select View | Quick Documentation from the main menu. The documentation will be shown in a popup, but you can configure the IDE to display it in the tool window right away.

Quick Documentation in the tool window

View documentation in the tool window

With the default settings, pressing Ctrl0Q (View | Quick Documentation) opens quick documentation in a popup. You can change the settings to view documentation in the tool window.

  • In the quick documentation popup, click the Show Options Menu icon and disable the Show Documentation Popup First option.

  • In the Documentation tool window, click the Show Options Menu icon on the tool window toolbar and disable the Show Documentation Popup First option.

Keep documentation in the tool window

You can open a piece of documentation for a specific code element in the tool window and keep viewing documentation for other elements in your current file.

  1. Place the caret at the required code element and press Ctrl0Q. If the popup appears, press Ctrl0Q again to switch to the tool window.

    The asterisk symbol (*) on the documentation tab means that the tab is not pinned, so its content will be replaced by documentation for another code element that you select in the editor.

  2. Right-click the tab with the documentation in the documentation tool window and enable the Keep This Documentation option.

    After that, the current documentation tab will be pinned. You can return to the editor and view documentation for other code elements that will open either in the popup or in a new tab in the tool window.

tip

Press Ctrl0F in the Documentation tool window to use the text search.

When you are viewing code documentation in the tool window, it is displayed on the unpinned tab (the tab marked with the asterisk symbol (*). There are several ways in which you can work with it:

You can view documentation by hovering over code elements.

Click the Options icon on the tool window toolbar and enable the Show on Mouse Move and Auto-Update from Source options.

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 more information about configuring library and SDK external documentation paths, refer to:

View external documentation

  • To view documentation for a symbol at the caret in a browser, press ShiftF1 or select View | External Documentation from the main menu.

Type Info

In IntelliJ IDEA, you can identify the type of an expression.

  • Place the caret at the necessary code element and press CtrlShift0P. Alternatively, 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 expression type information.

  • To view static information on Java expressions, place the caret at the expression and double-press CtrlShift0P.

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 Alt0Q.

See also

Getting Started