IntelliJ IDEA 2019.3 Help

Code reference information

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.

Click the Open as Tool Window icon in the top-right corner to open the definition in the Find tool window. To open the source code of the definition for editing and close the popup, click the Edit Source iconF4. To open the definition without closing the popup, click the Show Source Ctrl+Enter.

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).

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, seeInlay 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 Blacklist section.

  4. 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 Javadoc markup, or with documentation from an SDK. You can also supply your project with external documentation to be able to quickly view it in a popup.

  • To view documentation for a symbol at caret, press Ctrl+Q (or click View | Quick Documentation).

    You can press Ctrl+Q again to switch between the popup and the toolbar.

Quick Documentation popup

Click the Settings icon to change the font size, display the quick documentation toolbar, or go to the source code.

Automatically show quick documentation

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

  2. In the Other area, select the Show quick documentation on mouse move checkbox and specify the delay in milliseconds after which the popup should appear.

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 a quick documentation popup.

Configure the external documentation path

To view external documentation, you need to configure the documentation URL first.

  1. In the Project Structure dialogCtrl+Shift+Alt+S, select SDKs.

  2. Select the necessary JDK version if you have several JDKs configured, and open the Documentation Path tab on the right.

  3. Click the Specify URL icon and enter the external documentation URL. For example, for Java 12, type https://docs.oracle.com/en/java/javase/12/docs/api/).

  4. Apply the changes and close the dialog.

Access external documentation offline

If you work offline, you can view external documentation locally.

  1. Download the documentation package of the necessary version. The documentation package is normally distributed in a ZIP archive that you need to unpack once it is downloaded.

    For example, you can download the official Java SE Development Kit 8 Documentation and unzip it.

  2. In the Project Structure dialogCtrl+Shift+Alt+S, select SDKs.

  3. Select the necessary JDK version if you have several JDKs configured, and open the Documentation Path tab on the right.

  4. Click the Add icon and specify the directory with the downloaded documentation package (for example, C:\Users\john.doe\Desktop\docs\api).

  5. Apply the changes and close the dialog.

View external documentation

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

Type info

In IntelliJ IDEA, you can identify the type of any variable and an expression in a popup. This is helpful if you don't need the full information on the code element.

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

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-pressCtrl+Shift+P.

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 pressingAlt+Q.

Last modified: 20 March 2020