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package javax.sound.sampled;
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.
Author: Kara Kytle See Also: Since: 1.3
/**
* The {@code 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.
* <p>
* A line can have controls, such as gain, pan, and reverb. The controls
* themselves are instances of classes that extend the base {@link Control}
* class. The {@code Line} interface provides two accessor methods for obtaining
* the line's controls: {@link #getControls getControls} returns the entire set,
* and {@link #getControl getControl} returns a single control of specified
* type.
* <p>
* 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 {@link #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
* {@link SourceDataLine#write SourceDataLine.write} and
* {@link TargetDataLine#read TargetDataLine.read}.
* <p>
* You can register an object to receive notifications whenever the line's state
* changes. The object must implement the {@link LineListener} interface, which
* consists of the single method {@link LineListener#update update}. This method
* will be invoked when a line opens and closes (and, if it's a {@link DataLine}
* , when it starts and stops).
* <p>
* An object can be registered to listen to multiple lines. The event it
* receives in its {@code update} method will specify which line created the
* event, what type of event it was ({@code OPEN}, {@code CLOSE}, {@code START},
* or {@code STOP}), and how many sample frames the line had processed at the
* time the event occurred.
* <p>
* 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.
*
* @author Kara Kytle
* @see LineEvent
* @since 1.3
*/
public interface Line extends AutoCloseable {
Obtains the Line.Info object describing this line. Returns: description of the line
/**
* Obtains the {@code Line.Info} object describing this line.
*
* @return description of the line
*/
Line.Info getLineInfo();
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:
/**
* 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 {@code OPEN} event is dispatched to the line's
* listeners.
* <p>
* Note that some lines, once closed, cannot be reopened. Attempts to reopen
* such a line will always result in an {@code LineUnavailableException}.
* <p>
* Some types of lines have configurable properties that may affect resource
* allocation. For example, a {@code 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 {@code open}
* method or methods which allow an application to specify the desired
* settings.
* <p>
* This method takes no arguments, and opens the line with the current
* settings. For {@link SourceDataLine} and {@link TargetDataLine} objects,
* this means that the line is opened with default settings. For a
* {@link 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 {@code IllegalArgumentException} is thrown. Therefore, you
* should instead use one of the {@code open} methods provided in the
* {@code Clip} interface to load data into the {@code Clip}.
* <p>
* For {@code DataLine}'s, if the {@code 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
* @throws LineUnavailableException if the line cannot be opened due to
* resource restrictions
* @throws SecurityException if the line cannot be opened due to security
* restrictions
* @see #close
* @see #isOpen
* @see LineEvent
* @see DataLine
* @see Clip#open(AudioFormat, byte[], int, int)
* @see Clip#open(AudioInputStream)
*/
void open() throws LineUnavailableException;
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:
/**
* 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 {@code CLOSE} event is dispatched to the line's listeners.
*
* @throws SecurityException if the line cannot be closed due to security
* restrictions
* @see #open
* @see #isOpen
* @see LineEvent
*/
@Override
void close();
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.
See Also: Returns: true if the line is open, otherwise false
/**
* 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.
*
* @return {@code true} if the line is open, otherwise {@code false}
* @see #open()
* @see #close()
*/
boolean isOpen();
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.
See Also: Returns: the array of controls
/**
* 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.
*
* @return the array of controls
* @see #getControl
*/
Control[] getControls();
Indicates whether the line supports a control of the specified type. Some
controls may only be available when the line is open.
Params: - 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
/**
* Indicates whether the line supports a control of the specified type. Some
* controls may only be available when the line is open.
*
* @param control the type of the control for which support is queried
* @return {@code true} if at least one control of the specified type is
* supported, otherwise {@code false}
*/
boolean isControlSupported(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.
Params: - control – the type of the requested control
Throws: - IllegalArgumentException – if a control of the specified type is
not supported
See Also: Returns: a control of the specified type
/**
* Obtains a control of the specified type, if there is any. Some controls
* may only be available when the line is open.
*
* @param control the type of the requested control
* @return a control of the specified type
* @throws IllegalArgumentException if a control of the specified type is
* not supported
* @see #getControls
* @see #isControlSupported(Control.Type control)
*/
Control getControl(Control.Type control);
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. Params: - listener – the object to add as a listener to this line
See Also:
/**
* Adds a listener to this line. Whenever the line's status changes, the
* listener's {@code update()} method is called with a {@code LineEvent}
* object that describes the change.
*
* @param listener the object to add as a listener to this line
* @see #removeLineListener
* @see LineListener#update
* @see LineEvent
*/
void addLineListener(LineListener listener);
Removes the specified listener from this line's list of listeners.
Params: - listener – listener to remove
See Also:
/**
* Removes the specified listener from this line's list of listeners.
*
* @param listener listener to remove
* @see #addLineListener
*/
void removeLineListener(LineListener listener);
A Line.Info object contains information about a line. The only information provided by Line.Info itself is the Java class of the line. A subclass of Line.Info adds other kinds of information about the line. This additional information depends on which Line subinterface is implemented by the kind of line that the Line.Info subclass describes. A Line.Info can be retrieved using various methods of the Line, Mixer, and AudioSystem interfaces. Other such methods let you pass a Line.Info as an argument, to learn whether lines matching the specified configuration are available and to obtain them.
/**
* A {@code Line.Info} object contains information about a line. The only
* information provided by {@code Line.Info} itself is the Java class of the
* line. A subclass of {@code Line.Info} adds other kinds of information
* about the line. This additional information depends on which {@code Line}
* subinterface is implemented by the kind of line that the
* {@code Line.Info} subclass describes.
* <p>
* A {@code Line.Info} can be retrieved using various methods of the
* {@code Line}, {@code Mixer}, and {@code AudioSystem} interfaces. Other
* such methods let you pass a {@code Line.Info} as an argument, to learn
* whether lines matching the specified configuration are available and to
* obtain them.
*
* @author Kara Kytle
* @see Line#getLineInfo()
* @see Mixer#getSourceLineInfo()
* @see Mixer#getTargetLineInfo()
* @see Mixer#getLine(Line.Info)
* @see Mixer#getSourceLineInfo(Line.Info)
* @see Mixer#getTargetLineInfo(Line.Info)
* @see Mixer#isLineSupported(Line.Info)
* @see AudioSystem#getLine(Line.Info)
* @see AudioSystem#getSourceLineInfo(Line.Info)
* @see AudioSystem#getTargetLineInfo(Line.Info)
* @see AudioSystem#isLineSupported(Line.Info)
* @since 1.3
*/
class Info {
The class of the line described by the info object.
/**
* The class of the line described by the info object.
*/
private final Class<?> lineClass;
Constructs an info object that describes a line of the specified
class. This constructor is typically used by an application to
describe a desired line.
Params: - lineClass – the class of the line that the new
Line.Info object describes
/**
* Constructs an info object that describes a line of the specified
* class. This constructor is typically used by an application to
* describe a desired line.
*
* @param lineClass the class of the line that the new
* {@code Line.Info} object describes
*/
public Info(Class<?> lineClass) {
if (lineClass == null) {
this.lineClass = Line.class;
} else {
this.lineClass = lineClass;
}
}
Obtains the class of the line that this Line.Info object describes. Returns: the described line's class
/**
* Obtains the class of the line that this {@code Line.Info} object
* describes.
*
* @return the described line's class
*/
public Class<?> getLineClass() {
return lineClass;
}
Indicates whether the specified info object matches this one. To
match, the specified object must be identical to or a special case of
this one. The specified info object must be either an instance of the
same class as this one, or an instance of a sub-type of this one. In
addition, the attributes of the specified object must be compatible
with the capabilities of this one. Specifically, the routing
configuration for the specified info object must be compatible with
that of this one. Subclasses may add other criteria to determine
whether the two objects match.
Params: - info – the info object which is being compared to this one
Returns: true if the specified object matches this one, false otherwise
/**
* Indicates whether the specified info object matches this one. To
* match, the specified object must be identical to or a special case of
* this one. The specified info object must be either an instance of the
* same class as this one, or an instance of a sub-type of this one. In
* addition, the attributes of the specified object must be compatible
* with the capabilities of this one. Specifically, the routing
* configuration for the specified info object must be compatible with
* that of this one. Subclasses may add other criteria to determine
* whether the two objects match.
*
* @param info the info object which is being compared to this one
* @return {@code true} if the specified object matches this one,
* {@code false} otherwise
*/
public boolean matches(Info info) {
// $$kk: 08.30.99: is this backwards?
// dataLine.matches(targetDataLine) == true: targetDataLine is always dataLine
// targetDataLine.matches(dataLine) == false
// so if i want to make sure i get a targetDataLine, i need:
// targetDataLine.matches(prospective_match) == true
// => prospective_match may be other things as well, but it is at least a targetDataLine
// targetDataLine defines the requirements which prospective_match must meet.
// "if this Class object represents a declared class, this method returns
// true if the specified Object argument is an instance of the represented
// class (or of any of its subclasses)"
// GainControlClass.isInstance(MyGainObj) => true
// GainControlClass.isInstance(MySpecialGainInterfaceObj) => true
// this_class.isInstance(that_object) => that object can by cast to this class
// => that_object's class may be a subtype of this_class
// => that may be more specific (subtype) of this
// "If this Class object represents an interface, this method returns true
// if the class or any superclass of the specified Object argument implements
// this interface"
// GainControlClass.isInstance(MyGainObj) => true
// GainControlClass.isInstance(GenericControlObj) => may be false
// => that may be more specific
if (! (this.getClass().isInstance(info)) ) {
return false;
}
// this.isAssignableFrom(that) => this is same or super to that
// => this is at least as general as that
// => that may be subtype of this
if (! (getLineClass().isAssignableFrom(info.getLineClass())) ) {
return false;
}
return true;
}
Obtains a textual description of the line info.
Returns: a string description
/**
* Obtains a textual description of the line info.
*
* @return a string description
*/
@Override
public String toString() {
String fullPackagePath = "javax.sound.sampled.";
String initialString = new String(getLineClass().toString());
String finalString;
int index = initialString.indexOf(fullPackagePath);
if (index != -1) {
finalString = initialString.substring(0, index) + initialString.substring( (index + fullPackagePath.length()), initialString.length() );
} else {
finalString = initialString;
}
return finalString;
}
}
}