IntelliJ IDEA 2023.3 Help

Code completion

This section covers various techniques of context-aware code completion that allow you to speed up your coding process.

Basic completion

Basic code completion helps you complete the names of classes, methods, fields, and keywords within the visibility scope.

When you invoke code completion, IntelliJ IDEA analyzes the context and suggests the choices that are reachable from the current caret position (suggestions also include Live templates) .

If basic code completion is applied to a part of a field, parameter, or variable declaration, IntelliJ IDEA suggests a list of possible names depending on the item type.

Invoking basic code completion for the second time shows inaccessible classes and members (these can be made public by applying an intention action).

When invoked for the third time in a row, IntelliJ IDEA will look for suggestions for classes and interface names in the entire project, regardless of dependencies. If the necessary class is not yet imported, it will be imported automatically.

Invoke basic completion

  1. Start typing a name. By default, IntelliJ IDEA displays the code completion popup automatically as you type.

    If automatic completion is disabled, press Ctrl+Space or choose Code | Code Completion | Basic from the main menu.

    basicCodeCompletion.png
  2. If necessary, press Ctrl+Space for the second time (or press Ctrl+Alt+Space).

    This shows inaccessible classes and members as well as static fields and methods.

    codeCompletionSecondClass1.png
  3. When invoked for the third time, basic code completion expands the suggestion list to all classes throughout the project, regardless of the dependencies.

Type-matching completion

Smart type-matching code completion filters the suggestion list and shows only the types applicable to the current context.

Type-matching completion is useful in situations when it is possible to determine the appropriate type:

  • In the right part of assignment statements

  • In variable initializers

  • In return statements

  • In the list of arguments of a method call

  • After the new keyword in an object declaration

  • In chained expressions

Invoke type-matching completion

  1. Start typing. By default, IntelliJ IDEA displays the code completion popup automatically as you type. If automatic completion is disabled, press Ctrl+Shift+Space or choose Code | Code Completion | Type-Matching from the main menu.

    smart type-matching completion
  2. If necessary, press Ctrl+Shift+Space once again. This lets you complete:

    • Collections, lists and arrays. IntelliJ IDEA searches for symbols with the same component type and suggests converting them.

    • Static method calls or constant references. IntelliJ IDEA scans for static methods and fields, and suggests the ones suitable in the current context.

    smart type completion second call

Statement completion

You can create syntactically correct code constructs by using statement completion. It inserts the necessary syntax elements (parentheses, braces, and semicolons) and gets you in a position where you can start typing the next statement.

Complete a method declaration

  • Start typing a method declaration and press Ctrl+Shift+Enter after the opening parenthesis.

    complete a method declaration

Complete a code construct

  • Start typing a code construct and press Ctrl+Shift+Enter.

    IntelliJ IDEA automatically completes the construct and adds the required punctuation. The caret is placed at the next editing position.

    Complete a code construct

Wrap a method call argument

  • Type an expression. Then type a method call. When println gets the focus in the suggestion list, select it with Ctrl+Shift+Enter:

    Wrap a method call argument

Hippie completion

Hippie completion is a completion engine that analyses your text in the visible scope and generates suggestions from the current context. It helps you complete any word from any of the currently opened files.

Expand a string at caret to an existing word

  1. Type the initial string and do one of the following:

    • Press Alt+/ or choose Code | Code Completion | Cyclic Expand Word to search for matching words before the caret.

    • Press Alt+Shift+/ or choose Code | Code Completion | Cyclic Expand Word (Backward) to search for matching words after the caret and in other open files.

    The first suggested value appears, and the prototype is highlighted in the source code.

    Expand a string at caret to an existing word
  2. Accept the suggestion, or hold the Alt key and keep pressing / until the desired word is found.

Postfix code completion

Postfix code completion helps you reduce backward caret jumps as you write code. You can transform an already-typed expression to a different one based on a postfix you type after the dot, the type of expression, and its context.

Enable and configure postfix completion

  • In the Settings dialog (Ctrl+Alt+S), open Editor | General | Postfix Completion and select the Enable postfix completion checkbox.

  • Select Tab, Space, or Enter to be used for expanding postfix templates.

  • Enable/disable a particular postfix template for the selected language.

Transform a statement with a postfix

  • Type an expression and then type a postfix after a dot, for example, .if:

    public class Foo { void m(boolean b) { b.if } }
    fun foo(x: Boolean) { x.if }

    The initial expression gets wrapped with an if statement:

    public class Foo { void m(boolean b) { if (b) { } } }
    fun foo(x: Boolean) { if (x) { } }

You can disable certain postfix completion templates in the Editor | General | Postfix Completion page of the IDE settings  Ctrl+Alt+S.

You can select Tab, Space, or Enter to expand postfix templates.

You can edit the predefined postfix templates, for example, to replace a long key with a shorter one, or to expand the list of applicable expression types.

Create custom postfix templates

  1. Press Ctrl+Alt+S to open the IDE settings and then select Editor | General | Postfix Completion.

  2. Click the Add button (the Add button) on the toolbar.

  3. In the popup menu that opens, choose the language that you need to create a postfix template for.

  4. Specify Key, a combination of symbols that will invoke the template.

  5. Select which expression types the new template will be applicable to, and type the target expression in the following format: $EXPR$ <target_expression>, for example, $EXPR$ =!null.

  6. To have IntelliJ IDEA automatically transform the topmost applicable expression when the template is invoked, select the Apply to the topmost expression checkbox.

    Otherwise, if the checkbox is cleared, IntelliJ IDEA will prompt you to choose the expression when you invoke the template.

  7. Enable Use static import if possible: select this checkbox to have IntelliJ IDEA add static import statements instead of inserting MyUtils.methodName().

Completion of tags and attributes

IntelliJ IDEA automatically completes names and values of tags and attributes in many file types:

Completion of tags and attribute names is based on the DTD or Schema the file is associated with. If there is no schema association, IntelliJ IDEA will use the file content (tag and attribute names and their values) to complete your input.

In XML/XSL and JSP/JSPX files, completion for taglibs and namespaces is available.

Complete tag names

  1. Press &lt; and start typing the tag name. IntelliJ IDEA displays the list of tag names appropriate in the current context.

    Tags completion

    Use the Up and Down buttons to scroll through the list.

  2. Press Enter to accept a selection from the list. If your file is associated with a schema or a DTD, IntelliJ IDEA automatically inserts the mandatory attributes according to it.

Import a taglib declaration

If you need to use tags declared in a tag library, you need to import this taglib before any custom tag from it can be used.

  1. Start typing a taglib prefix and press Alt+Insert.

  2. Select a taglib from the list and press Enter.

    Import taglib declaration

    IntelliJ IDEA imports the selected taglib and adds the import statement automatically.

Insert a tag declared in a taglib

  1. Start typing a tag and press Ctrl+Alt+Space.

  2. Select a tag from the list. The uri of the taglib it belongs to is displayed in brackets.

    Tag completion: before
  3. Select the desired taglib and press Enter. IntelliJ IDEA adds the declaration of the selected taglib:

    Tag completion: after

Machine-learning-assisted code completion

IntelliJ IDEA allows you to prioritize completion suggestions based on choices that other users made in similar situations.

The ML completion mechanism doesn't add any new elements but orders the elements retrieved from code. Data is not exposed anywhere; it is collected locally.

Enable ML completion

  1. Press Ctrl+Alt+S to open the IDE settings and select Editor | General | Code Completion.

  2. Under Machine Learning Completion Ranking, enable the Sort completion suggestions based on machine learning option, and select the languages for which you want to use ML completion.

    ML-assisted completion settings

Enable relevance markers

  1. Press Ctrl+Alt+S to open the IDE settings and select Editor | General | Code Completion.

  2. Enable the following options:

    • Mark position changes in the completion popup: use the Machine Learning ranking Up and Machine Learning ranking Down icons to indicate whether the relevance of a suggestion is increasing or decreasing and therefore the suggestion has moved up or down the suggestion list.

    • Mark the most relevant item in the completion popup: use the ML relevant proposal icon to indicate the most suitable suggestion on the list.

    The suggestion list will look as follows with the icons marking reordered and the most relevant items.

    ML-assisted completion

Configure code completion settings

To configure code completion options, go to the Editor | General | Code Completion page of the IDE settings  Ctrl+Alt+S.

You can choose the following settings:

Item

Description

Match case

Select if you want the letter case to be taken into account for completion suggestions. Choose whether you want to match the case for the first letter or for all letters.

Automatically insert single suggestions for

Automatically complete code if there's just one suggestion for basic and smart type-matching completion.

Sort suggestions alphabetically

Select if you want to sort items in the suggestion list in the alphabetical order instead of sorting them by relevance.

You can change this behavior at any time by clicking in the suggestion list and toggling the Sort by Name option.

Show suggestions as you type

Select if you want the suggestion list to be invoked automatically, without having to call completion explicitly. This option is enabled by default.

Insert selected suggestion by pressing space, dot, or other context-dependent keys

Select if you want to insert the selected suggestion by typing certain keys that depend on the language, your context, and so on. For Java, such keys include Space, Tab, [ and ], ( and ), and some more.

Show the documentation popup in

Select to automatically show a popup for each item in the suggestion list with the documentation for the class, method, or field currently highlighted in the lookup list.

In the field to the right, specify the delay (in milliseconds), after which the popup should appear.

Insert parentheses automatically when applicable

If this option is enabled, IntelliJ IDEA automatically inserts a pair of opening and closing parentheses when you complete a function/method.

Insert parentheses on completion is enabled

Clear the checkbox to suppress inserting parentheses automatically.

If you use an opening parentheses ( instead of Enter to apply the selected item from a completion list, parentheses will be inserted automatically no matter whether the option is turned on or off.

Insert parentheses on completion is disabled. Parentheses are still inserted on completion with an opening brace.

To use an opening parentheses ( instead of Enter to apply the selected item from a completion list, open the Settings dialog (Ctrl+Alt+S) , go to Editor | General | Code Completion, and select the Insert selected suggestion by pressing space, dot, or other context-dependent keys checkbox.

For more information, refer to Use specific keys to insert suggestions.

Machine Learning-Assisted Completion

Sort completion suggestions based on machine learning

Select this option if you want to use machine learning models to rank the most suitable items higher in the suggestion list. Select the languages for which you want to enable suggestions based on Machine Learning.

Mark position changes in the completion popup

Use the Machine Learning ranking Up and Machine Learning ranking Down icons to indicate whether the relevance of a suggestion is increasing or decreasing and therefore the suggestion has moved up or down the suggestion list.

Mark the most relevant item in the completion popup

Use the ML relevant proposal icon to indicate the most suitable suggestion on the list.

JavaScript

Only type-based completion

By default, IntelliJ IDEA suggests completion for symbols regardless of their types. With this approach, in complicated cases the list shows multiple completion variants.

To make completion more precise, select this option. The completion list will strongly depend on the IntelliJ IDEA inference. As a result, the list may remain empty in case of poor inference.

Suggest items with optional chaining for nullable types

By default, IntelliJ IDEA suggests completion for symbols with the optional chaining operator (?). Clear this checkbox to suppress this behavior.

Expand method bodies in completion for overrides

By default, when you want to override a method from the parent class or interface and select this method from the list of completion suggestions, IntelliJ IDEA automatically adds parameters, generates a super() call, and adds the type information, if possible.

Clear this checkbox to suppress automatic generation of method bodies for overrides during completion.

Completion of names

  • Suggest variable and parameter names: By default, the checkbox is cleared. When it is selected, IntelliJ IDEA suggests names for new variables and parameters during their declaration. These suggestions are based on the names of classes, types, and interfaces that are defined in your project, in the libraries you are using, and in standard APIs.

  • Suggest names for class fields

    The option is turned off by default.

  • Add type annotations for suggested parameter names: Select this checkbox to supply each completion suggestion with information on its type.

    The checkbox is available only when the Suggest variable and parameter names checkbox is selected.

Parameter Info

Show parameter name hints on completion

Select if you want hints for parameter values to be displayed.

Show the parameter info popup (in ms)

Select this checkbox to have IntelliJ IDEA automatically show a popup with all available method signatures when an opening bracket is typed in the editor, or a method is selected from the suggestion list.

In the text field to the right, specify the delay (in milliseconds) after when the popup window should appear.

If this checkbox is not selected, use Ctrl+P to show parameter info.

Show full method signatures

If this checkbox is selected, the parameter info displays full signatures, including method name and returned type.

SQL

Use aliases in completion for JOIN

Creates aliases for tables in the JOIN statement.

Use aliases in completion for JOIN

Invert order of operands in auto-generated ON clause

Switches operands in the ON clause. When the checkbox is cleared, the FROM table comes the first in the JOIN condition.

Invert order of operands in auto-generated ON clause

Automatically add aliases when completing table names

Creates an alias for a table name.

Automatically add aliases when completing table names

Suggest alias names in completion after table names

Suggests an alias for a table name when you use code completion (Ctrl+Space).

Suggest alias names in completion after table names

Custom aliases (table)

You can add a table name and the alias that you want to use for this table. To add the table-alias pair, click the Add alias button (the Add alias button).

Exclude a class or package from completion

  1. Press Ctrl+Alt+S to open the IDE settings and then select Editor | General | Auto Import.

  2. Under Exclude from import and completion, add the names of classes or packages that you want to exclude from completion. The classes you specify here will not appear in the suggestion list.

You can also select a completion suggestion when it appears in the editor: press Alt+Enter and select Exclude from there:

Exclude from completion

Completion tips and tricks

Open completion settings from the completion popup

You can quickly access code completion settings right from the completion popup.

  • Click the icon in the completion popup and select Code Completion Settings.

    Opening completion settings

After that, the Editor | General | Code Completion page of the IDE settings  Ctrl+Alt+S opens.

Narrow down the suggestion list

  • You can narrow down the suggestion list by typing any part of a word (even characters from somewhere in the middle) or invoking code completion after a dot separator . IntelliJ IDEA will show suggestions that include the characters you have entered in any positions.

    This makes the use of wildcards unnecessary:

    codeCompletionWildcard.png

    In case of CamelCase or snake_case names, type the initial letters only. IntelliJ IDEA automatically recognizes and matches the initial letters.

Accept a suggestion

You can accept a suggestion from the list in one of the following ways:

  • Press Enter or double-click a list item to insert it to the left of the caret.

  • Press Tab to replace the characters to the right from the caret.

  • Use Ctrl+Shift+Enter to make the current code construct syntactically correct (balance parentheses, add missing braces and semicolons, and so on).

You can also use specific keys to insert the selected completion suggestion: go to the Editor | General | Code Completion page of the IDE settings  Ctrl+Alt+S and select the Insert the selected suggestion by pressing space, dot, or other context-dependent keys option. These keys depend on the language, your context, and so on. For Java, such keys include Space, Tab, [ and ], ( and ), and some more.

Negate an expression

You can negate an expression in Java by pressing ! after you have selected it from the suggestion list. As a result, the expression will be negated:

negate an expression

Negating an expression works this way if you have the Insert selected suggestion by pressing space, dot, or other context-dependent keys option enabled in the Code Completion settings page, or invoke code completion explicitly, or change a selection in the suggestion list explicitly.

    Completion shortcuts

    You can use the following live templates shortcuts for one of the most frequently used statements:

    • sout: prints System.out.printIn()

    • soutm: adds the current class and method names

    • soutp: adds method parameter names and values

    • soutv: adds the last variable value

    • soutc: inserts the System.out::printIn method reference where a consumer function is expected

    View reference

    • You can use the Quick Definition view by pressing Ctrl+Shift+I when you select an entry in the suggestion list:

      Quick definition
    • You can use the Quick Documentation by pressing Ctrl+Q when you select an entry in the suggestion list:

      Quick documentation

    View code hierarchy

    You can view code hierarchy when you've selected an entry from the suggestion list:

    • Ctrl+H - view type hierarchy

    • Ctrl+Alt+H - view call hierarchy.

    • Ctrl+Shift+H - view method hierarchy.

    Watch this video to learn more about how completion works in IntelliJ IDEA:

    Troubleshooting

    If code completion doesn't work, this may be due to one of the following reasons:

    • The Power Save Mode is on (File | Power Save Mode). Turning it on minimizes power consumption of your laptop by eliminating the background operations, including error highlighting, on-the-fly inspections, and code completion.

    • JDK is not configured for your project.

    • Your file doesn't reside in a content root and is not bound to a build path, so it doesn't get the required class definitions and resources needed for code completion.

    • A file containing classes and methods that you want to appear in the completion suggestion list is marked as a plain text file.

    • External libraries that contain methods that you want to appear in the completion suggestion list are not added as dependencies or global libraries.

    • Code completion popup might not appear automatically if it takes too long to gather the completion options. For example, if the computer is busy with another task. In this case, you may still activate the completion popup manually via Ctrl+Space hotkey.

    Last modified: 15 March 2024