Java IO.pdf - Nguyen Dang Binh

17.5.5.1 Step 1
Java I/O
As you would probably guess, you listen for parallel port events with a Parallel-
PortEventListener:
public interface ParallelPortEventListener extends EventListener
This interface declares a single method, parallelEvent():
public abstract void parallelEvent(ParallelPortEvent ppe)
Inside this method, you generally use the getEventType() method of Parallel-PortEvent
to determine exactly what caused the parallel port event:
public int getEventType()
This should return ParallelPortEvent.PAR_EV_BUFFER to signal an empty output buffer or
ParallelPortEvent.PAR_EV_ERROR to signal some other sort of error.
The getNewValue() and getOldValue() methods tell you what the state of the parallel port
was before and after the event:
public boolean getNewValue()
public boolean getOldValue()
17.5.5.2 Step 2
Once you've constructed a ParallelPortEventListener, you need to pass it to the
ParallelPort object's addEventListener() method:
public abstract void addEventListener(ParallelPortEventListener listener)
throws TooManyListenersException
You are limited to one event listener per port. Attempting to add a second event listener
throws a java.util.TooManyListenersException. If this is a problem, you can install a
single intermediate event listener directly with the ParallelPort object, which keeps a list of
ParallelPortEventListener objects and dispatches events it receives to the other event
listeners.
Should you need to, you can remove a listener from the port with the ParallelPort object's
removeEventListener() method:
public abstract void removeEventListener()
This method takes no arguments, because there's never more than one event listener registered
directly with the port.
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