edu.oswego.cs.dl.util.concurrent
Class Latch
java.lang.Object
|
+--edu.oswego.cs.dl.util.concurrent.Latch
- All Implemented Interfaces:
- Sync
- public class Latch
- extends Object
- implements Sync
A latch is a boolean condition that is set at most once, ever.
Once a single release is issued, all acquires will pass.
Sample usage. Here are a set of classes that use
a latch as a start signal for a group of worker threads that
are created and started beforehand, and then later enabled.
class Worker implements Runnable {
private final Latch startSignal;
Worker(Latch l) { startSignal = l; }
public void run() {
startSignal.acquire();
doWork();
}
void doWork() { ... }
}
class Driver { // ...
void main() {
Latch go = new Latch();
for (int i = 0; i < N; ++i) // make threads
new Thread(new Worker(go)).start();
doSomethingElse(); // don't let run yet
go.release(); // let all threads proceed
}
}
[ Introduction to this package. ]
Constructor Summary |
Latch()
|
Method Summary |
void |
acquire()
Wait (possibly forever) until successful passage. |
boolean |
attempt(long msecs)
Wait at most msecs to pass; report whether passed. |
void |
release()
Enable all current and future acquires to pass |
Latch
public Latch()
acquire
public void acquire()
throws InterruptedException
- Description copied from interface:
Sync
- Wait (possibly forever) until successful passage.
Fail only upon interuption. Interruptions always result in
`clean' failures. On failure, you can be sure that it has not
been acquired, and that no
corresponding release should be performed. Conversely,
a normal return guarantees that the acquire was successful.
- Specified by:
acquire
in interface Sync
attempt
public boolean attempt(long msecs)
throws InterruptedException
- Description copied from interface:
Sync
- Wait at most msecs to pass; report whether passed.
The method has best-effort semantics:
The msecs bound cannot
be guaranteed to be a precise upper bound on wait time in Java.
Implementations generally can only attempt to return as soon as possible
after the specified bound. Also, timers in Java do not stop during garbage
collection, so timeouts can occur just because a GC intervened.
So, msecs arguments should be used in
a coarse-grained manner. Further,
implementations cannot always guarantee that this method
will return at all without blocking indefinitely when used in
unintended ways. For example, deadlocks may be encountered
when called in an unintended context.
- Specified by:
attempt
in interface Sync
- Following copied from interface:
edu.oswego.cs.dl.util.concurrent.Sync
- Parameters:
msecs
- the number of milleseconds to wait.
An argument less than or equal to zero means not to wait at all.
However, this may still require
access to a synchronization lock, which can impose unbounded
delay if there is a lot of contention among threads.- Returns:
- true if acquired
release
public void release()
- Enable all current and future acquires to pass
- Specified by:
release
in interface Sync
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