IntelliJ IDEA 2018.2 Help

Code completion

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

Basic completion: names and keywords

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.
  2. Press Ctrl+Space or choose Code | Completion | Basic from the main menu.
    basicCodeCompletion.png
  3. 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
  4. 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 based on type

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.
  2. Press Ctrl+Shift+Space or choose Code | Completion | SmartType from the main menu.

    The most suitable suggestion for the current context is highlighted.

    img

    For chained expressions, suggestions are sorted by how frequently they are used in the project. When any of the suggested method calls takes an argument that is not yet available in the context, after you select it the IDE defines a local variable of the required type.

  3. 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.

Statements completion

Statements completion enables you to create syntactically correct code constructs. It inserts the necessary syntax elements (parentheses, braces, semicolons etc.) 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.
    completePunctuation1
    completePunctuation2

Complete a code construct

  • Start typing a code construct and press Ctrl+Shift+Enter.
    completePunctuation3.png
    IntelliJ IDEA automatically completes the construct and adds the required punctuation, and the caret is placed at the next editing position.
    completePunctuation4.png

Wrap a method call argument

  1. Type an expression, for example
    "test"
  2. Type a method call. When println gets the focus in the suggestion list, select it with Ctrl+Shift+Enter:
    autoEncapsulation

    The resulting code will look like the following:

    System.out.println("test");

Hippie completion: expanding words based on context

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

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 also choose which key you want to use to expand postfix templates: Tab, Space, or Enter.

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

Create custom postfix templates

  1. In the Settings/Preferences dialog (Ctrl+Alt+S), select Editor | General | Postfix Completion.
  2. Click icons general add svg on the toolbar.
  3. Specify the Key, i.e. 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 the 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 ArrowUp and ArrowDown 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.
    import2

    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.
    tagCompletionBefore
  3. Select the desired taglib and press Enter. IntelliJ IDEA adds the declaration of the selected taglib:
    tagCompletionAfter

Configure code completion settings

Configure completion options

  1. In the Settings/Preferences dialog (Ctrl+Alt+S), select Editor | General | Code Completion.
  2. Do the following:
    • To automatically display the suggestions list, select the Show suggestions as you type checkbox. If the checkbox is cleared, you have to call code completion explicitly by pressing Ctrl+Space for basic completion or Ctrl+Shift+Space for smart completion.

      You can also choose to automatically insert suggestions when there's just one option: select the completion type under Automatically insert single suggestions for.

    • To sort suggestions in the alphabetical order, instead of sorting them by relevance, select the Sort suggestions alphabetically checkbox.

      You can also toggle these modes by clicking a icon or pi icon respectively in the lower-right corner of the suggestions list.

    • If you want case to be taken into account when suggesting completion options, select Match case and choose whether you want to match case for first letters only, or for all letters.
    • If you want the documentation popup to be displayed automatically for each item in the suggestions list as you scroll it, select the Show documentation popup in option. In the field to the right, specify the delay (in milliseconds), after which the pop-up window should appear.

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, etc.)

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, etc. 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:

negateExpression1
As a result, the expression will be negated:
negateExpression2

Negating an expression works this way if you have the Insert selected variant by typing dot, space, etc. 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 Quick Definition View by pressing Ctrl+Shift+I when you select an entry in the suggestions list:
    lookupListQuickDefView
  • You can use the Quick Information View by pressing Ctrl+Q when you select an entry in the suggestions list:
    lookupListQuickDocView

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.

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 completion suggestions list are not added as dependencies or global libraries.
Last modified: 4 September 2018

See Also

Reference:

Getting Started: