IntelliJ IDEA 2020.2 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 analyses 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.

Smart completion

Smart code completion filters the suggestions list and shows only the types applicable to the current context.

Smart 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 smart 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 | SmartType from the main menu.

    smart type 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.

    expandWord1.png
  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.

  • To view a full list of available postfix templates, in the Settings/Preferences dialog Ctrl+Alt+S, go to Editor | General | Postfix Completion.

  • Select Tab, Space, or Enter to expand postfix templates.

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) { } }

To disable certain postfix completion templates, in the Settings/Preferences dialog Ctrl+Alt+S select Editor | General | Postfix Completion.

You can selectTab, 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. In the Settings/Preferences dialog Ctrl+Alt+S, go to Editor | General | Postfix Completion.

  2. Click the Add button on the toolbar.

  3. Specify the Key, that is the combination of symbols that will invoke the template, 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.

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 < 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

Configure code completion settings

To configure code completion options, In the Settings/Preferences dialog Ctrl+Alt+S go to Editor | General | Code Completion.

You can choose the following settings:

Item

Description

Match caseSelect if you want letter case to be taken into account for completion suggestions. Choose whether you want to match case for the first letter or for all letters.
Automatically insert single suggestions for Select if you want to automatically complete code if there's just one suggestion for basic and/or smart completion.
Sort suggestions alphabetically

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

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

Show suggestions as you type Select if you want the suggestions 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 keysSelect 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 suggestions 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.

Rank completion suggestions based on Machine Learning

Select if you want to utilize machine learning models to rank most suitable items higher in the suggestions 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 suggestions 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. In the Settings/Preferences dialog Ctrl+Alt+S 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 suggestions 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

Narrow down the suggestions list

  • You can narrow down the suggestions 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've 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: in the Settings/Preferences dialog Ctrl+Alt+S choose Editor | General | Code Completion and select the Insert 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 suggestions 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 suggestions 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

    View reference

    • You can use the Definitions by pressing Ctrl+Shift+I when you select an entry in the suggestions list:

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

      Quick documentation

    View code hierarchy

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

    • Ctrl+H - view type hierarchy

    • Ctrl+Alt+H - view call hierarchy.

    • Ctrl+Shift+H - view method hierarchy.

    Use machine-learning-assisted code completion

    You can utilize machine learning models to rank most suitable items higher in the suggestions list.

    To do this, in the Settings/Preferences dialog Ctrl+Alt+S go to Editor | General | Code Completion and enable the Rank completion suggestions based on Machine Learning option under Machine Learning-Assisted Completion.

      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 completion suggestions list is marked as a plain text file.

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

      Last modified: 23 July 2020