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*
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package javax.sound.sampled;
/**
* 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 {@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 {@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 {@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.
*
* @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.
*
* @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.
*
* @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.
*
* @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 {@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.
*
* @param listener listener to remove
* @see #addLineListener
*/
void removeLineListener(LineListener listener);
/**
* 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.
*/
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.
*
* @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 {@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.
*
* @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
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