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Tab Completion

JLine provides a powerful tab completion system that allows you to add intelligent suggestions to your command-line applications. This page explains how to configure and use the tab completion feature.

Basic Completers​

JLine provides several built-in completers for common use cases:

StringsCompleter​

The StringsCompleter completes from a fixed or dynamic set of strings:

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FileNameCompleter​

The FileNameCompleter completes file and directory names:

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TreeCompleter​

The TreeCompleter allows you to define a hierarchical structure of completions:

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AggregateCompleter​

The AggregateCompleter combines multiple completers:

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Custom Completers​

You can create your own completers by implementing the Completer interface:

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Completion Behavior​

You can configure how completion behaves:

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Candidates with Descriptions​

You can provide descriptions for completion candidates:

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Context-Aware Completion​

You can create completers that are aware of the current context:

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Colored Completions​

You can add colors to your completions:

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Additional Completers​

JLine provides several additional completers for specific use cases:

NullCompleter​

The NullCompleter is used to terminate completion:

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DirectoriesCompleter​

The DirectoriesCompleter completes only directory names:

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FilesCompleter​

The FilesCompleter completes file names with filtering:

Loading snippet: FilesCompleterExample...

RegexCompleter​

The RegexCompleter uses regular expressions to define completion patterns:

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EnumCompleter​

The EnumCompleter completes enum values:

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Builtins Completers​

The JLine Builtins module provides additional completers:

SystemCompleter​

The SystemCompleter manages completers for different commands:

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Builtins TreeCompleter​

The Builtins module provides its own TreeCompleter:

Loading snippet: BuiltinsTreeCompleterExample...

Best Practices​

When implementing tab completion in JLine, consider these best practices:

  1. Combine Completers: Use AggregateCompleter and ArgumentCompleter to create complex completion behavior.

  2. Context-Aware Completion: Make your completers aware of the current context for more intelligent suggestions.

  3. Descriptions: Provide descriptions for completion candidates to help users understand their options.

  4. Colored Completions: Use colors to distinguish between different types of completions.

  5. Dynamic Completions: Update completion candidates based on the current state of your application.

  6. Filtering: Filter completion candidates based on what the user has typed so far.

  7. Performance: Be mindful of performance, especially for large sets of completion candidates.

  8. Testing: Test your completers thoroughly with different inputs.

  9. Documentation: Document the available completions for your users.

  10. Fallbacks: Provide sensible fallbacks when specific completions are not available.