public interface

Line

javax.sound.sampled.Line
Known Indirect Subclasses

Class Overview

The Line interface represents a mono or multi-channel audio feed. A line is an element of the digital audio "pipeline," such as a mixer, an input or output port, or a data path into or out of a mixer.

A line can have controls, such as gain, pan, and reverb. The controls themselves are instances of classes that extend the base Control class. The Line interface provides two accessor methods for obtaining the line's controls: getControls returns the entire set, and getControl returns a single control of specified type.

Lines exist in various states at different times. When a line opens, it reserves system resources for itself, and when it closes, these resources are freed for other objects or applications. The isOpen() method lets you discover whether a line is open or closed. An open line need not be processing data, however. Such processing is typically initiated by subinterface methods such as SourceDataLine.write and TargetDataLine.read.

You can register an object to receive notifications whenever the line's state changes. The object must implement the LineListener interface, which consists of the single method update. This method will be invoked when a line opens and closes (and, if it's a DataLine, when it starts and stops).

An object can be registered to listen to multiple lines. The event it receives in its update method will specify which line created the event, what type of event it was (OPEN, CLOSE, START, or STOP), and how many sample frames the line had processed at the time the event occurred.

Certain line operations, such as open and close, can generate security exceptions if invoked by unprivileged code when the line is a shared audio resource.

See Also

Summary

Nested Classes
class Line.Info A Line.Info object contains information about a line. 
Public Methods
abstract void addLineListener(LineListener listener)
Adds a listener to this line.
abstract void close()
Closes the line, indicating that any system resources in use by the line can be released.
abstract Control getControl(Control.Type control)
Obtains a control of the specified type, if there is any.
abstract Control[] getControls()
Obtains the set of controls associated with this line.
abstract Line.Info getLineInfo()
Obtains the Line.Info object describing this line.
abstract boolean isControlSupported(Control.Type control)
Indicates whether the line supports a control of the specified type.
abstract boolean isOpen()
Indicates whether the line is open, meaning that it has reserved system resources and is operational, although it might not currently be playing or capturing sound.
abstract void open()
Opens the line, indicating that it should acquire any required system resources and become operational.
abstract void removeLineListener(LineListener listener)
Removes the specified listener from this line's list of listeners.

Public Methods

public abstract void addLineListener (LineListener listener)

Adds a listener to this line. Whenever the line's status changes, the listener's update() method is called with a LineEvent object that describes the change.

Parameters
listener the object to add as a listener to this line
See Also

public abstract void close ()

Closes the line, indicating that any system resources in use by the line can be released. If this operation succeeds, the line is marked closed and a CLOSE event is dispatched to the line's listeners.

Throws
SecurityException if the line cannot be closed due to security restrictions.
See Also

public abstract Control getControl (Control.Type control)

Obtains a control of the specified type, if there is any. Some controls may only be available when the line is open.

Parameters
control the type of the requested control
Returns
  • a control of the specified type
Throws
IllegalArgumentException if a control of the specified type is not supported
See Also

public abstract Control[] getControls ()

Obtains the set of controls associated with this line. Some controls may only be available when the line is open. If there are no controls, this method returns an array of length 0.

Returns
  • the array of controls
See Also

public abstract Line.Info getLineInfo ()

Obtains the Line.Info object describing this line.

Returns
  • description of the line

public abstract boolean isControlSupported (Control.Type control)

Indicates whether the line supports a control of the specified type. Some controls may only be available when the line is open.

Parameters
control the type of the control for which support is queried
Returns
  • true if at least one control of the specified type is supported, otherwise false.

public abstract boolean isOpen ()

Indicates whether the line is open, meaning that it has reserved system resources and is operational, although it might not currently be playing or capturing sound.

Returns
  • true if the line is open, otherwise false
See Also

public abstract void open ()

Opens the line, indicating that it should acquire any required system resources and become operational. If this operation succeeds, the line is marked as open, and an OPEN event is dispatched to the line's listeners.

Note that some lines, once closed, cannot be reopened. Attempts to reopen such a line will always result in an LineUnavailableException.

Some types of lines have configurable properties that may affect resource allocation. For example, a DataLine must be opened with a particular format and buffer size. Such lines should provide a mechanism for configuring these properties, such as an additional open method or methods which allow an application to specify the desired settings.

This method takes no arguments, and opens the line with the current settings. For SourceDataLine and TargetDataLine objects, this means that the line is opened with default settings. For a Clip, however, the buffer size is determined when data is loaded. Since this method does not allow the application to specify any data to load, an IllegalArgumentException is thrown. Therefore, you should instead use one of the open methods provided in the Clip interface to load data into the Clip.

For DataLine's, if the DataLine.Info object which was used to retrieve the line, specifies at least one fully qualified audio format, the last one will be used as the default format.

Throws
IllegalArgumentException if this method is called on a Clip instance.
LineUnavailableException if the line cannot be opened due to resource restrictions.
SecurityException if the line cannot be opened due to security restrictions.
See Also

public abstract void removeLineListener (LineListener listener)

Removes the specified listener from this line's list of listeners.

Parameters
listener listener to remove
See Also