Exchanger<V>
Java SE 6
| public class java.util.concurrent Exchanger<V>
|
Java SE 6 |
exchange method, matches with a partner thread,
and receives its partner's object on return. An Exchanger may be
viewed as a bidirectional form of a SynchronousQueue.
Exchangers may be useful in applications such as genetic algorithms
and pipeline designs.
Sample Usage:
Here are the highlights of a class that uses an Exchanger
to swap buffers between threads so that the thread filling the
buffer gets a freshly emptied one when it needs it, handing off the
filled one to the thread emptying the buffer.
class FillAndEmpty {
Exchanger<DataBuffer> exchanger = new Exchanger<DataBuffer>();
DataBuffer initialEmptyBuffer = ... a made-up type
DataBuffer initialFullBuffer = ...
class FillingLoop implements Runnable {
public void run() {
DataBuffer currentBuffer = initialEmptyBuffer;
try {
while (currentBuffer != null) {
addToBuffer(currentBuffer);
if (currentBuffer.isFull())
currentBuffer = exchanger.exchange(currentBuffer);
} catch (InterruptedException ex) { ... handle ... }
}
}
class EmptyingLoop implements Runnable {
public void run() {
DataBuffer currentBuffer = initialFullBuffer;
try {
while (currentBuffer != null) {
takeFromBuffer(currentBuffer);
if (currentBuffer.isEmpty())
currentBuffer = exchanger.exchange(currentBuffer);
}
} catch (InterruptedException ex) { ... handle ...}
}
}
void start() {
new Thread(new FillingLoop()).start();
new Thread(new EmptyingLoop()).start();
}
}
}Memory consistency effects: For each pair of threads that
successfully exchange objects via an Exchanger, actions
prior to the exchange() in each thread
happen-before
those subsequent to a return from the corresponding exchange()
in the other thread.
| since | 1.5 |
| V | The type of objects that may be exchanged |
| Constructors | |
|---|---|
| public | Exchanger() Creates a new Exchanger. |
| Methods | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| public Object | exchange(Object x) throws InterruptedException Waits for another thread to arrive at this exchange point (unless the current thread is interrupted), and then transfers the given object to it, receiving its object in return. If another thread is already waiting at the exchange point then it is resumed for thread scheduling purposes and receives the object passed in by the current thread. The current thread returns immediately, receiving the object passed to the exchange by that other thread. If no other thread is already waiting at the exchange then the current thread is disabled for thread scheduling purposes and lies dormant until one of two things happens:
If the current thread:
InterruptedException is thrown and the current thread's
interrupted status is cleared.
| ||||||||||||
| public Object | exchange(Object x, long timeout, TimeUnit unit) throws InterruptedException, TimeoutException Waits for another thread to arrive at this exchange point (unless the current thread is interrupted or the specified waiting time elapses), and then transfers the given object to it, receiving its object in return. If another thread is already waiting at the exchange point then it is resumed for thread scheduling purposes and receives the object passed in by the current thread. The current thread returns immediately, receiving the object passed to the exchange by that other thread. If no other thread is already waiting at the exchange then the current thread is disabled for thread scheduling purposes and lies dormant until one of three things happens:
If the current thread:
InterruptedException is thrown and the current thread's
interrupted status is cleared.
If the specified waiting time elapses then
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