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Interactive Features

JLine provides several advanced features that enhance the interactive experience of command-line applications. This guide covers some of the most powerful interactive features: PrintAboveWriter, LineReader#printAbove, Status, and Tailtips.

PrintAboveWriter and LineReader#printAbove​

One of JLine's most powerful features is the ability to print text above the current input line. This is particularly useful for displaying asynchronous information (like notifications or progress updates) without disrupting the user's input.

Using LineReader#printAbove​

The simplest way to print above the current line is to use the printAbove method of the LineReader class:

Loading snippet: PrintAboveExample...

In this example, notifications will appear above the input line, and the user can continue typing without interruption.

Using PrintAboveWriter​

For more control, you can use the PrintAboveWriter class:

Loading snippet: PrintAboveWriterExample...

The PrintAboveWriter class provides a standard PrintWriter interface, making it easy to integrate with existing code that expects a PrintWriter.

Best Practices​

When using these features, keep these best practices in mind:

  1. Use sparingly: Too many messages can be distracting.
  2. Keep messages concise: Long messages may wrap and take up too much screen space.
  3. Consider styling: Use colors and styles to differentiate types of messages.
  4. Flush the writer: Always call flush() after writing to ensure the message is displayed immediately.
  5. Thread safety: Access to the terminal should be synchronized if multiple threads are writing to it.

Status Line​

JLine's Status feature allows you to display persistent status information at the bottom of the terminal. This is useful for showing application state, connection status, or other contextual information.

Basic Status Usage​

Loading snippet: StatusExample...

Dynamic Status Updates​

You can update the status line dynamically to reflect changes in your application's state:

Loading snippet: DynamicStatusExample...

Status with Multiple Segments​

You can create a more complex status line with multiple segments:

Loading snippet: MultiSegmentStatusExample...

Best Practices​

When using these interactive features, keep these guidelines in mind:

  1. Consistency: Use consistent styling and positioning for similar types of information.
  2. Clarity: Make sure the information is clear and concise.
  3. Performance: Update the status and tailtips only when necessary to avoid performance issues.
  4. Accessibility: Don't rely solely on colors for conveying information.
  5. Thread safety: Synchronize access to shared resources when updating from multiple threads.

These interactive features can significantly enhance the user experience of your command-line application, making it more informative and responsive.