Sample usages: * - *
A Phaser may be used instead of a {@code CountDownLatch} to control - * a one-shot action serving a variable number of parties. The typical - * idiom is for the method setting this up to first register, then - * start the actions, then deregister, as in: + *
A {@code Phaser} may be used instead of a {@code CountDownLatch} + * to control a one-shot action serving a variable number of + * parties. The typical idiom is for the method setting this up to + * first register, then start the actions, then deregister, as in: * *
{@code
* void runTasks(List list) {
* final Phaser phaser = new Phaser(1); // "1" to register self
+ * // create and start threads
* for (Runnable r : list) {
* phaser.register();
* new Thread() {
* public void run() {
* phaser.arriveAndAwaitAdvance(); // await all creation
* r.run();
- * phaser.arriveAndDeregister(); // signal completion
* }
* }.start();
* }
*
- * doSomethingOnBehalfOfWorkers();
- * phaser.arrive(); // allow threads to start
- * int p = phaser.arriveAndDeregister(); // deregister self ...
- * p = phaser.awaitAdvance(p); // ... and await arrival
- * otherActions(); // do other things while tasks execute
- * phaser.awaitAdvance(p); // await final completion
+ * // allow threads to start and deregister self
+ * phaser.arriveAndDeregister();
* }}
*
* One way to cause a set of threads to repeatedly perform actions @@ -139,9 +137,9 @@ import java.util.concurrent.locks.LockSu * phaser.arriveAndDeregister(); // deregister self, don't wait * }} * - *
To create a set of tasks using a tree of Phasers, + *
To create a set of tasks using a tree of phasers, * you could use code of the following form, assuming a - * Task class with a constructor accepting a Phaser that + * Task class with a constructor accepting a phaser that * it registers for upon construction: *
{@code
* void build(Task[] actions, int lo, int hi, Phaser b) {
@@ -249,7 +247,7 @@ public class Phaser {
private final Phaser parent;
/**
- * The root of Phaser tree. Equals this if not in a tree. Used to
+ * The root of phaser tree. Equals this if not in a tree. Used to
* support faster state push-down.
*/
private final Phaser root;
@@ -300,16 +298,16 @@ public class Phaser {
}
/**
- * Creates a new Phaser without any initially registered parties,
+ * Creates a new phaser without any initially registered parties,
* initial phase number 0, and no parent. Any thread using this
- * Phaser will need to first register for it.
+ * phaser will need to first register for it.
*/
public Phaser() {
this(null);
}
/**
- * Creates a new Phaser with the given numbers of registered
+ * Creates a new phaser with the given numbers of registered
* unarrived parties, initial phase number 0, and no parent.
*
* @param parties the number of parties required to trip barrier
@@ -321,7 +319,7 @@ public class Phaser {
}
/**
- * Creates a new Phaser with the given parent, without any
+ * Creates a new phaser with the given parent, without any
* initially registered parties. If parent is non-null this phaser
* is registered with the parent and its initial phase number is
* the same as that of parent phaser.
@@ -341,7 +339,7 @@ public class Phaser {
}
/**
- * Creates a new Phaser with the given parent and numbers of
+ * Creates a new phaser with the given parent and numbers of
* registered unarrived parties. If parent is non-null, this phaser
* is registered with the parent and its initial phase number is
* the same as that of parent phaser.
@@ -463,11 +461,12 @@ public class Phaser {
}
/**
- * Arrives at the barrier, and deregisters from it, without
- * waiting for others. Deregistration reduces number of parties
+ * Arrives at the barrier and deregisters from it without waiting
+ * for others. Deregistration reduces the number of parties
* required to trip the barrier in future phases. If this phaser
* has a parent, and deregistration causes this phaser to have
- * zero parties, this phaser is also deregistered from its parent.
+ * zero parties, this phaser also arrives at and is deregistered
+ * from its parent.
*
* @return the current barrier phase number upon entry to
* this method, or a negative value if terminated
@@ -520,9 +519,11 @@ public class Phaser {
/**
* Arrives at the barrier and awaits others. Equivalent in effect
- * to {@code awaitAdvance(arrive())}. If you instead need to
- * await with interruption of timeout, and/or deregister upon
- * arrival, you can arrange them using analogous constructions.
+ * to {@code awaitAdvance(arrive())}. If you need to await with
+ * interruption or timeout, you can arrange this with an analogous
+ * construction using one of the other forms of the awaitAdvance
+ * method. If instead you need to deregister upon arrival use
+ * {@code arriveAndDeregister}.
*
* @return the phase on entry to this method
* @throws IllegalStateException if not terminated and the number
@@ -533,9 +534,10 @@ public class Phaser {
}
/**
- * Awaits the phase of the barrier to advance from the given
- * value, or returns immediately if argument is negative or this
- * barrier is terminated.
+ * Awaits the phase of the barrier to advance from the given phase
+ * value, returning immediately if the current phase of the
+ * barrier is not equal to the given phase value or this barrier
+ * is terminated.
*
* @param phase the phase on entry to this method
* @return the phase on exit from this method
@@ -554,10 +556,11 @@ public class Phaser {
}
/**
- * Awaits the phase of the barrier to advance from the given
- * value, or returns immediately if argument is negative or this
- * barrier is terminated, or throws InterruptedException if
- * interrupted while waiting.
+ * Awaits the phase of the barrier to advance from the given phase
+ * value, throwing InterruptedException if interrupted while
+ * waiting, or returning immediately if the current phase of the
+ * barrier is not equal to the given phase value or this barrier
+ * is terminated
*
* @param phase the phase on entry to this method
* @return the phase on exit from this method
@@ -577,11 +580,17 @@ public class Phaser {
}
/**
- * Awaits the phase of the barrier to advance from the given value
- * or the given timeout elapses, or returns immediately if
- * argument is negative or this barrier is terminated.
+ * Awaits the phase of the barrier to advance from the given phase
+ * value or the given timeout elapses, throwing
+ * InterruptedException if interrupted while waiting, or returning
+ * immediately if the current phase of the barrier is not equal to
+ * the given phase value or this barrier is terminated.
*
* @param phase the phase on entry to this method
+ * @param timeout how long to wait before giving up, in units of
+ * {@code unit}
+ * @param unit a {@code TimeUnit} determining how to interpret the
+ * {@code timeout} parameter
* @return the phase on exit from this method
* @throws InterruptedException if thread interrupted while waiting
* @throws TimeoutException if timed out while waiting
@@ -636,16 +645,6 @@ public class Phaser {
}
/**
- * Returns {@code true} if the current phase number equals the given phase.
- *
- * @param phase the phase
- * @return {@code true} if the current phase number equals the given phase
- */
- public final boolean hasPhase(int phase) {
- return phaseOf(getReconciledState()) == phase;
- }
-
- /**
* Returns the number of parties registered at this barrier.
*
* @return the number of parties
@@ -711,21 +710,17 @@ public class Phaser {
* termination state, and subsequent calls to {@link #isTerminated}
* will return true.
*
- * The default version returns {@code true} when the number of
+ *
The default version returns {@code true} when the number of
* registered parties is zero. Normally, overrides that arrange
* termination for other reasons should also preserve this
* property.
*
- *
You may override this method to perform an action with side
+ *
You may override this method to perform an action with side
* effects visible to participating tasks, but it is in general
* only sensible to do so in designs where all parties register
- * before any arrive, and all {@code awaitAdvance} at each phase.
- * Otherwise, you cannot ensure lack of interference. In
- * particular, this method may be invoked more than once per
- * transition if other parties successfully register while the
- * invocation of this method is in progress, thus postponing the
- * transition until those parties also arrive, re-triggering this
- * method.
+ * before any arrive, and all {@link #awaitAdvance} at each phase.
+ * Otherwise, you cannot ensure lack of interference from other
+ * parties during the invocation of this method.
*
* @param phase the phase number on entering the barrier
* @param registeredParties the current number of registered parties