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Posted to commits@harmony.apache.org by nd...@apache.org on 2006/08/24 05:42:33 UTC
svn commit: r434296 [5/19] - in /incubator/harmony/enhanced/classlib/trunk:
make/ modules/concurrent/ modules/concurrent/.settings/
modules/concurrent/META-INF/ modules/concurrent/make/
modules/concurrent/src/ modules/concurrent/src/main/ modules/concu...
Added: incubator/harmony/enhanced/classlib/trunk/modules/concurrent/src/main/java/java/util/concurrent/RejectedExecutionHandler.java
URL: http://svn.apache.org/viewvc/incubator/harmony/enhanced/classlib/trunk/modules/concurrent/src/main/java/java/util/concurrent/RejectedExecutionHandler.java?rev=434296&view=auto
==============================================================================
--- incubator/harmony/enhanced/classlib/trunk/modules/concurrent/src/main/java/java/util/concurrent/RejectedExecutionHandler.java (added)
+++ incubator/harmony/enhanced/classlib/trunk/modules/concurrent/src/main/java/java/util/concurrent/RejectedExecutionHandler.java Wed Aug 23 20:42:25 2006
@@ -0,0 +1,33 @@
+/*
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/licenses/publicdomain
+ */
+
+package java.util.concurrent;
+
+/**
+ * A handler for tasks that cannot be executed by a {@link
+ * ThreadPoolExecutor}.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ */
+public interface RejectedExecutionHandler {
+
+ /**
+ * Method that may be invoked by a {@link ThreadPoolExecutor} when
+ * <tt>execute</tt> cannot accept a task. This may occur when no
+ * more threads or queue slots are available because their bounds
+ * would be exceeded, or upon shutdown of the Executor.
+ *
+ * In the absence other alternatives, the method may throw an
+ * unchecked {@link RejectedExecutionException}, which will be
+ * propagated to the caller of <tt>execute</tt>.
+ *
+ * @param r the runnable task requested to be executed
+ * @param executor the executor attempting to execute this task
+ * @throws RejectedExecutionException if there is no remedy
+ */
+ void rejectedExecution(Runnable r, ThreadPoolExecutor executor);
+}
Propchange: incubator/harmony/enhanced/classlib/trunk/modules/concurrent/src/main/java/java/util/concurrent/RejectedExecutionHandler.java
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Added: incubator/harmony/enhanced/classlib/trunk/modules/concurrent/src/main/java/java/util/concurrent/ScheduledExecutorService.java
URL: http://svn.apache.org/viewvc/incubator/harmony/enhanced/classlib/trunk/modules/concurrent/src/main/java/java/util/concurrent/ScheduledExecutorService.java?rev=434296&view=auto
==============================================================================
--- incubator/harmony/enhanced/classlib/trunk/modules/concurrent/src/main/java/java/util/concurrent/ScheduledExecutorService.java (added)
+++ incubator/harmony/enhanced/classlib/trunk/modules/concurrent/src/main/java/java/util/concurrent/ScheduledExecutorService.java Wed Aug 23 20:42:25 2006
@@ -0,0 +1,145 @@
+/*
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/licenses/publicdomain
+ */
+
+package java.util.concurrent;
+import java.util.concurrent.atomic.*;
+import java.util.*;
+
+/**
+ * An {@link ExecutorService} that can schedule commands to run after a given
+ * delay, or to execute periodically.
+ *
+ * <p> The <tt>schedule</tt> methods create tasks with various delays
+ * and return a task object that can be used to cancel or check
+ * execution. The <tt>scheduleAtFixedRate</tt> and
+ * <tt>scheduleWithFixedDelay</tt> methods create and execute tasks
+ * that run periodically until cancelled.
+ *
+ * <p> Commands submitted using the {@link Executor#execute} and
+ * {@link ExecutorService} <tt>submit</tt> methods are scheduled with
+ * a requested delay of zero. Zero and negative delays (but not
+ * periods) are also allowed in <tt>schedule</tt> methods, and are
+ * treated as requests for immediate execution.
+ *
+ * <p>All <tt>schedule</tt> methods accept <em>relative</em> delays and
+ * periods as arguments, not absolute times or dates. It is a simple
+ * matter to transform an absolute time represented as a {@link
+ * java.util.Date} to the required form. For example, to schedule at
+ * a certain future <tt>date</tt>, you can use: <tt>schedule(task,
+ * date.getTime() - System.currentTimeMillis(),
+ * TimeUnit.MILLISECONDS)</tt>. Beware however that expiration of a
+ * relative delay need not coincide with the current <tt>Date</tt> at
+ * which the task is enabled due to network time synchronization
+ * protocols, clock drift, or other factors.
+ *
+ * The {@link Executors} class provides convenient factory methods for
+ * the ScheduledExecutorService implementations provided in this package.
+ *
+ * <h3>Usage Example</h3>
+ *
+ * Here is a class with a method that sets up a ScheduledExecutorService
+ * to beep every ten seconds for an hour:
+ *
+ * <pre>
+ * import static java.util.concurrent.TimeUnit;
+ * class BeeperControl {
+ * private final ScheduledExecutorService scheduler =
+ * Executors.newScheduledThreadPool(1);
+ *
+ * public void beepForAnHour() {
+ * final Runnable beeper = new Runnable() {
+ * public void run() { System.out.println("beep"); }
+ * };
+ * final ScheduledFuture<?> beeperHandle =
+ * scheduler.scheduleAtFixedRate(beeper, 10, 10, SECONDS);
+ * scheduler.schedule(new Runnable() {
+ * public void run() { beeperHandle.cancel(true); }
+ * }, 60 * 60, SECONDS);
+ * }
+ * }
+ * </pre>
+ *
+ * @since 1.5
+ * @author Doug Lea
+ */
+public interface ScheduledExecutorService extends ExecutorService {
+
+ /**
+ * Creates and executes a one-shot action that becomes enabled
+ * after the given delay.
+ * @param command the task to execute.
+ * @param delay the time from now to delay execution.
+ * @param unit the time unit of the delay parameter.
+ * @return a Future representing pending completion of the task,
+ * and whose <tt>get()</tt> method will return <tt>null</tt>
+ * upon completion.
+ * @throws RejectedExecutionException if task cannot be scheduled
+ * for execution.
+ * @throws NullPointerException if command is null
+ */
+ public ScheduledFuture<?> schedule(Runnable command, long delay, TimeUnit unit);
+
+ /**
+ * Creates and executes a ScheduledFuture that becomes enabled after the
+ * given delay.
+ * @param callable the function to execute.
+ * @param delay the time from now to delay execution.
+ * @param unit the time unit of the delay parameter.
+ * @return a ScheduledFuture that can be used to extract result or cancel.
+ * @throws RejectedExecutionException if task cannot be scheduled
+ * for execution.
+ * @throws NullPointerException if callable is null
+ */
+ public <V> ScheduledFuture<V> schedule(Callable<V> callable, long delay, TimeUnit unit);
+
+ /**
+ * Creates and executes a periodic action that becomes enabled first
+ * after the given initial delay, and subsequently with the given
+ * period; that is executions will commence after
+ * <tt>initialDelay</tt> then <tt>initialDelay+period</tt>, then
+ * <tt>initialDelay + 2 * period</tt>, and so on.
+ * If any execution of the task
+ * encounters an exception, subsequent executions are suppressed.
+ * Otherwise, the task will only terminate via cancellation or
+ * termination of the executor.
+ * @param command the task to execute.
+ * @param initialDelay the time to delay first execution.
+ * @param period the period between successive executions.
+ * @param unit the time unit of the initialDelay and period parameters
+ * @return a Future representing pending completion of the task,
+ * and whose <tt>get()</tt> method will throw an exception upon
+ * cancellation.
+ * @throws RejectedExecutionException if task cannot be scheduled
+ * for execution.
+ * @throws NullPointerException if command is null
+ * @throws IllegalArgumentException if period less than or equal to zero.
+ */
+ public ScheduledFuture<?> scheduleAtFixedRate(Runnable command, long initialDelay, long period, TimeUnit unit);
+
+ /**
+ * Creates and executes a periodic action that becomes enabled first
+ * after the given initial delay, and subsequently with the
+ * given delay between the termination of one execution and the
+ * commencement of the next. If any execution of the task
+ * encounters an exception, subsequent executions are suppressed.
+ * Otherwise, the task will only terminate via cancellation or
+ * termination of the executor.
+ * @param command the task to execute.
+ * @param initialDelay the time to delay first execution.
+ * @param delay the delay between the termination of one
+ * execution and the commencement of the next.
+ * @param unit the time unit of the initialDelay and delay parameters
+ * @return a Future representing pending completion of the task,
+ * and whose <tt>get()</tt> method will throw an exception upon
+ * cancellation.
+ * @throws RejectedExecutionException if task cannot be scheduled
+ * for execution.
+ * @throws NullPointerException if command is null
+ * @throws IllegalArgumentException if delay less than or equal to zero.
+ */
+ public ScheduledFuture<?> scheduleWithFixedDelay(Runnable command, long initialDelay, long delay, TimeUnit unit);
+
+}
Propchange: incubator/harmony/enhanced/classlib/trunk/modules/concurrent/src/main/java/java/util/concurrent/ScheduledExecutorService.java
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Added: incubator/harmony/enhanced/classlib/trunk/modules/concurrent/src/main/java/java/util/concurrent/ScheduledFuture.java
URL: http://svn.apache.org/viewvc/incubator/harmony/enhanced/classlib/trunk/modules/concurrent/src/main/java/java/util/concurrent/ScheduledFuture.java?rev=434296&view=auto
==============================================================================
--- incubator/harmony/enhanced/classlib/trunk/modules/concurrent/src/main/java/java/util/concurrent/ScheduledFuture.java (added)
+++ incubator/harmony/enhanced/classlib/trunk/modules/concurrent/src/main/java/java/util/concurrent/ScheduledFuture.java Wed Aug 23 20:42:25 2006
@@ -0,0 +1,19 @@
+/*
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/licenses/publicdomain
+ */
+
+package java.util.concurrent;
+
+/**
+ * A delayed result-bearing action that can be cancelled.
+ * Usually a scheduled future is the result of scheduling
+ * a task with a {@link ScheduledExecutorService}.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ * @param <V> The result type returned by this Future
+ */
+public interface ScheduledFuture<V> extends Delayed, Future<V> {
+}
Propchange: incubator/harmony/enhanced/classlib/trunk/modules/concurrent/src/main/java/java/util/concurrent/ScheduledFuture.java
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Added: incubator/harmony/enhanced/classlib/trunk/modules/concurrent/src/main/java/java/util/concurrent/ScheduledThreadPoolExecutor.java
URL: http://svn.apache.org/viewvc/incubator/harmony/enhanced/classlib/trunk/modules/concurrent/src/main/java/java/util/concurrent/ScheduledThreadPoolExecutor.java?rev=434296&view=auto
==============================================================================
--- incubator/harmony/enhanced/classlib/trunk/modules/concurrent/src/main/java/java/util/concurrent/ScheduledThreadPoolExecutor.java (added)
+++ incubator/harmony/enhanced/classlib/trunk/modules/concurrent/src/main/java/java/util/concurrent/ScheduledThreadPoolExecutor.java Wed Aug 23 20:42:25 2006
@@ -0,0 +1,541 @@
+/*
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/licenses/publicdomain
+ */
+
+package java.util.concurrent;
+import java.util.concurrent.atomic.*;
+import java.util.*;
+
+/**
+ * A {@link ThreadPoolExecutor} that can additionally schedule
+ * commands to run after a given delay, or to execute
+ * periodically. This class is preferable to {@link java.util.Timer}
+ * when multiple worker threads are needed, or when the additional
+ * flexibility or capabilities of {@link ThreadPoolExecutor} (which
+ * this class extends) are required.
+ *
+ * <p> Delayed tasks execute no sooner than they are enabled, but
+ * without any real-time guarantees about when, after they are
+ * enabled, they will commence. Tasks scheduled for exactly the same
+ * execution time are enabled in first-in-first-out (FIFO) order of
+ * submission.
+ *
+ * <p>While this class inherits from {@link ThreadPoolExecutor}, a few
+ * of the inherited tuning methods are not useful for it. In
+ * particular, because it acts as a fixed-sized pool using
+ * <tt>corePoolSize</tt> threads and an unbounded queue, adjustments
+ * to <tt>maximumPoolSize</tt> have no useful effect.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ */
+public class ScheduledThreadPoolExecutor
+ extends ThreadPoolExecutor
+ implements ScheduledExecutorService {
+
+ /**
+ * False if should cancel/suppress periodic tasks on shutdown.
+ */
+ private volatile boolean continueExistingPeriodicTasksAfterShutdown;
+
+ /**
+ * False if should cancel non-periodic tasks on shutdown.
+ */
+ private volatile boolean executeExistingDelayedTasksAfterShutdown = true;
+
+ /**
+ * Sequence number to break scheduling ties, and in turn to
+ * guarantee FIFO order among tied entries.
+ */
+ private static final AtomicLong sequencer = new AtomicLong(0);
+
+ /** Base of nanosecond timings, to avoid wrapping */
+ private static final long NANO_ORIGIN = System.nanoTime();
+
+ /**
+ * Returns nanosecond time offset by origin
+ */
+ final long now() {
+ return System.nanoTime() - NANO_ORIGIN;
+ }
+
+ private class ScheduledFutureTask<V>
+ extends FutureTask<V> implements ScheduledFuture<V> {
+
+ /** Sequence number to break ties FIFO */
+ private final long sequenceNumber;
+ /** The time the task is enabled to execute in nanoTime units */
+ private long time;
+ /**
+ * Period in nanoseconds for repeating tasks. A positive
+ * value indicates fixed-rate execution. A negative value
+ * indicates fixed-delay execution. A value of 0 indicates a
+ * non-repeating task.
+ */
+ private final long period;
+
+ /**
+ * Creates a one-shot action with given nanoTime-based trigger time
+ */
+ ScheduledFutureTask(Runnable r, V result, long ns) {
+ super(r, result);
+ this.time = ns;
+ this.period = 0;
+ this.sequenceNumber = sequencer.getAndIncrement();
+ }
+
+ /**
+ * Creates a periodic action with given nano time and period
+ */
+ ScheduledFutureTask(Runnable r, V result, long ns, long period) {
+ super(r, result);
+ this.time = ns;
+ this.period = period;
+ this.sequenceNumber = sequencer.getAndIncrement();
+ }
+
+ /**
+ * Creates a one-shot action with given nanoTime-based trigger
+ */
+ ScheduledFutureTask(Callable<V> callable, long ns) {
+ super(callable);
+ this.time = ns;
+ this.period = 0;
+ this.sequenceNumber = sequencer.getAndIncrement();
+ }
+
+ public long getDelay(TimeUnit unit) {
+ long d = unit.convert(time - now(), TimeUnit.NANOSECONDS);
+ return d;
+ }
+
+ public int compareTo(Object other) {
+ if (other == this) // compare zero ONLY if same object
+ return 0;
+ ScheduledFutureTask<?> x = (ScheduledFutureTask<?>)other;
+ long diff = time - x.time;
+ if (diff < 0)
+ return -1;
+ else if (diff > 0)
+ return 1;
+ else if (sequenceNumber < x.sequenceNumber)
+ return -1;
+ else
+ return 1;
+ }
+
+ /**
+ * Returns true if this is a periodic (not a one-shot) action.
+ * @return true if periodic
+ */
+ boolean isPeriodic() {
+ return period != 0;
+ }
+
+ /**
+ * Run a periodic task
+ */
+ private void runPeriodic() {
+ boolean ok = ScheduledFutureTask.super.runAndReset();
+ boolean down = isShutdown();
+ // Reschedule if not cancelled and not shutdown or policy allows
+ if (ok && (!down ||
+ (getContinueExistingPeriodicTasksAfterShutdownPolicy() &&
+ !isTerminating()))) {
+ long p = period;
+ if (p > 0)
+ time += p;
+ else
+ time = now() - p;
+ ScheduledThreadPoolExecutor.super.getQueue().add(this);
+ }
+ // This might have been the final executed delayed
+ // task. Wake up threads to check.
+ else if (down)
+ interruptIdleWorkers();
+ }
+
+ /**
+ * Overrides FutureTask version so as to reset/requeue if periodic.
+ */
+ public void run() {
+ if (isPeriodic())
+ runPeriodic();
+ else
+ ScheduledFutureTask.super.run();
+ }
+ }
+
+ /**
+ * Specialized variant of ThreadPoolExecutor.execute for delayed tasks.
+ */
+ private void delayedExecute(Runnable command) {
+ if (isShutdown()) {
+ reject(command);
+ return;
+ }
+ // Prestart a thread if necessary. We cannot prestart it
+ // running the task because the task (probably) shouldn't be
+ // run yet, so thread will just idle until delay elapses.
+ if (getPoolSize() < getCorePoolSize())
+ prestartCoreThread();
+
+ super.getQueue().add(command);
+ }
+
+ /**
+ * Cancel and clear the queue of all tasks that should not be run
+ * due to shutdown policy.
+ */
+ private void cancelUnwantedTasks() {
+ boolean keepDelayed = getExecuteExistingDelayedTasksAfterShutdownPolicy();
+ boolean keepPeriodic = getContinueExistingPeriodicTasksAfterShutdownPolicy();
+ if (!keepDelayed && !keepPeriodic)
+ super.getQueue().clear();
+ else if (keepDelayed || keepPeriodic) {
+ Object[] entries = super.getQueue().toArray();
+ for (int i = 0; i < entries.length; ++i) {
+ Object e = entries[i];
+ if (e instanceof ScheduledFutureTask) {
+ ScheduledFutureTask<?> t = (ScheduledFutureTask<?>)e;
+ if (t.isPeriodic()? !keepPeriodic : !keepDelayed)
+ t.cancel(false);
+ }
+ }
+ entries = null;
+ purge();
+ }
+ }
+
+ public boolean remove(Runnable task) {
+ if (!(task instanceof ScheduledFutureTask))
+ return false;
+ return getQueue().remove(task);
+ }
+
+ /**
+ * Creates a new ScheduledThreadPoolExecutor with the given core
+ * pool size.
+ *
+ * @param corePoolSize the number of threads to keep in the pool,
+ * even if they are idle.
+ * @throws IllegalArgumentException if corePoolSize less than or
+ * equal to zero
+ */
+ public ScheduledThreadPoolExecutor(int corePoolSize) {
+ super(corePoolSize, Integer.MAX_VALUE, 0, TimeUnit.NANOSECONDS,
+ new DelayedWorkQueue());
+ }
+
+ /**
+ * Creates a new ScheduledThreadPoolExecutor with the given
+ * initial parameters.
+ *
+ * @param corePoolSize the number of threads to keep in the pool,
+ * even if they are idle.
+ * @param threadFactory the factory to use when the executor
+ * creates a new thread.
+ * @throws NullPointerException if threadFactory is null
+ */
+ public ScheduledThreadPoolExecutor(int corePoolSize,
+ ThreadFactory threadFactory) {
+ super(corePoolSize, Integer.MAX_VALUE, 0, TimeUnit.NANOSECONDS,
+ new DelayedWorkQueue(), threadFactory);
+ }
+
+ /**
+ * Creates a new ScheduledThreadPoolExecutor with the given
+ * initial parameters.
+ *
+ * @param corePoolSize the number of threads to keep in the pool,
+ * even if they are idle.
+ * @param handler the handler to use when execution is blocked
+ * because the thread bounds and queue capacities are reached.
+ * @throws NullPointerException if handler is null
+ */
+ public ScheduledThreadPoolExecutor(int corePoolSize,
+ RejectedExecutionHandler handler) {
+ super(corePoolSize, Integer.MAX_VALUE, 0, TimeUnit.NANOSECONDS,
+ new DelayedWorkQueue(), handler);
+ }
+
+ /**
+ * Creates a new ScheduledThreadPoolExecutor with the given
+ * initial parameters.
+ *
+ * @param corePoolSize the number of threads to keep in the pool,
+ * even if they are idle.
+ * @param threadFactory the factory to use when the executor
+ * creates a new thread.
+ * @param handler the handler to use when execution is blocked
+ * because the thread bounds and queue capacities are reached.
+ * @throws NullPointerException if threadFactory or handler is null
+ */
+ public ScheduledThreadPoolExecutor(int corePoolSize,
+ ThreadFactory threadFactory,
+ RejectedExecutionHandler handler) {
+ super(corePoolSize, Integer.MAX_VALUE, 0, TimeUnit.NANOSECONDS,
+ new DelayedWorkQueue(), threadFactory, handler);
+ }
+
+ public ScheduledFuture<?> schedule(Runnable command,
+ long delay,
+ TimeUnit unit) {
+ if (command == null || unit == null)
+ throw new NullPointerException();
+ long triggerTime = now() + unit.toNanos(delay);
+ ScheduledFutureTask<?> t =
+ new ScheduledFutureTask<Boolean>(command, null, triggerTime);
+ delayedExecute(t);
+ return t;
+ }
+
+ public <V> ScheduledFuture<V> schedule(Callable<V> callable,
+ long delay,
+ TimeUnit unit) {
+ if (callable == null || unit == null)
+ throw new NullPointerException();
+ if (delay < 0) delay = 0;
+ long triggerTime = now() + unit.toNanos(delay);
+ ScheduledFutureTask<V> t =
+ new ScheduledFutureTask<V>(callable, triggerTime);
+ delayedExecute(t);
+ return t;
+ }
+
+ public ScheduledFuture<?> scheduleAtFixedRate(Runnable command,
+ long initialDelay,
+ long period,
+ TimeUnit unit) {
+ if (command == null || unit == null)
+ throw new NullPointerException();
+ if (period <= 0)
+ throw new IllegalArgumentException();
+ if (initialDelay < 0) initialDelay = 0;
+ long triggerTime = now() + unit.toNanos(initialDelay);
+ ScheduledFutureTask<?> t =
+ new ScheduledFutureTask<Object>(command,
+ null,
+ triggerTime,
+ unit.toNanos(period));
+ delayedExecute(t);
+ return t;
+ }
+
+ public ScheduledFuture<?> scheduleWithFixedDelay(Runnable command,
+ long initialDelay,
+ long delay,
+ TimeUnit unit) {
+ if (command == null || unit == null)
+ throw new NullPointerException();
+ if (delay <= 0)
+ throw new IllegalArgumentException();
+ if (initialDelay < 0) initialDelay = 0;
+ long triggerTime = now() + unit.toNanos(initialDelay);
+ ScheduledFutureTask<?> t =
+ new ScheduledFutureTask<Boolean>(command,
+ null,
+ triggerTime,
+ unit.toNanos(-delay));
+ delayedExecute(t);
+ return t;
+ }
+
+
+ /**
+ * Execute command with zero required delay. This has effect
+ * equivalent to <tt>schedule(command, 0, anyUnit)</tt>. Note
+ * that inspections of the queue and of the list returned by
+ * <tt>shutdownNow</tt> will access the zero-delayed
+ * {@link ScheduledFuture}, not the <tt>command</tt> itself.
+ *
+ * @param command the task to execute
+ * @throws RejectedExecutionException at discretion of
+ * <tt>RejectedExecutionHandler</tt>, if task cannot be accepted
+ * for execution because the executor has been shut down.
+ * @throws NullPointerException if command is null
+ */
+ public void execute(Runnable command) {
+ if (command == null)
+ throw new NullPointerException();
+ schedule(command, 0, TimeUnit.NANOSECONDS);
+ }
+
+ // Override AbstractExecutorService methods
+
+ public Future<?> submit(Runnable task) {
+ return schedule(task, 0, TimeUnit.NANOSECONDS);
+ }
+
+ public <T> Future<T> submit(Runnable task, T result) {
+ return schedule(Executors.callable(task, result),
+ 0, TimeUnit.NANOSECONDS);
+ }
+
+ public <T> Future<T> submit(Callable<T> task) {
+ return schedule(task, 0, TimeUnit.NANOSECONDS);
+ }
+
+ /**
+ * Set policy on whether to continue executing existing periodic
+ * tasks even when this executor has been <tt>shutdown</tt>. In
+ * this case, these tasks will only terminate upon
+ * <tt>shutdownNow</tt>, or after setting the policy to
+ * <tt>false</tt> when already shutdown. This value is by default
+ * false.
+ * @param value if true, continue after shutdown, else don't.
+ * @see #getExecuteExistingDelayedTasksAfterShutdownPolicy
+ */
+ public void setContinueExistingPeriodicTasksAfterShutdownPolicy(boolean value) {
+ continueExistingPeriodicTasksAfterShutdown = value;
+ if (!value && isShutdown())
+ cancelUnwantedTasks();
+ }
+
+ /**
+ * Get the policy on whether to continue executing existing
+ * periodic tasks even when this executor has been
+ * <tt>shutdown</tt>. In this case, these tasks will only
+ * terminate upon <tt>shutdownNow</tt> or after setting the policy
+ * to <tt>false</tt> when already shutdown. This value is by
+ * default false.
+ * @return true if will continue after shutdown.
+ * @see #setContinueExistingPeriodicTasksAfterShutdownPolicy
+ */
+ public boolean getContinueExistingPeriodicTasksAfterShutdownPolicy() {
+ return continueExistingPeriodicTasksAfterShutdown;
+ }
+
+ /**
+ * Set policy on whether to execute existing delayed
+ * tasks even when this executor has been <tt>shutdown</tt>. In
+ * this case, these tasks will only terminate upon
+ * <tt>shutdownNow</tt>, or after setting the policy to
+ * <tt>false</tt> when already shutdown. This value is by default
+ * true.
+ * @param value if true, execute after shutdown, else don't.
+ * @see #getExecuteExistingDelayedTasksAfterShutdownPolicy
+ */
+ public void setExecuteExistingDelayedTasksAfterShutdownPolicy(boolean value) {
+ executeExistingDelayedTasksAfterShutdown = value;
+ if (!value && isShutdown())
+ cancelUnwantedTasks();
+ }
+
+ /**
+ * Get policy on whether to execute existing delayed
+ * tasks even when this executor has been <tt>shutdown</tt>. In
+ * this case, these tasks will only terminate upon
+ * <tt>shutdownNow</tt>, or after setting the policy to
+ * <tt>false</tt> when already shutdown. This value is by default
+ * true.
+ * @return true if will execute after shutdown.
+ * @see #setExecuteExistingDelayedTasksAfterShutdownPolicy
+ */
+ public boolean getExecuteExistingDelayedTasksAfterShutdownPolicy() {
+ return executeExistingDelayedTasksAfterShutdown;
+ }
+
+
+ /**
+ * Initiates an orderly shutdown in which previously submitted
+ * tasks are executed, but no new tasks will be accepted. If the
+ * <tt>ExecuteExistingDelayedTasksAfterShutdownPolicy</tt> has
+ * been set <tt>false</tt>, existing delayed tasks whose delays
+ * have not yet elapsed are cancelled. And unless the
+ * <tt>ContinueExistingPeriodicTasksAfterShutdownPolicy</tt> has
+ * been set <tt>true</tt>, future executions of existing periodic
+ * tasks will be cancelled.
+ */
+ public void shutdown() {
+ cancelUnwantedTasks();
+ super.shutdown();
+ }
+
+ /**
+ * Attempts to stop all actively executing tasks, halts the
+ * processing of waiting tasks, and returns a list of the tasks that were
+ * awaiting execution.
+ *
+ * <p>There are no guarantees beyond best-effort attempts to stop
+ * processing actively executing tasks. This implementation
+ * cancels tasks via {@link Thread#interrupt}, so if any tasks mask or
+ * fail to respond to interrupts, they may never terminate.
+ *
+ * @return list of tasks that never commenced execution. Each
+ * element of this list is a {@link ScheduledFuture},
+ * including those tasks submitted using <tt>execute</tt>, which
+ * are for scheduling purposes used as the basis of a zero-delay
+ * <tt>ScheduledFuture</tt>.
+ */
+ public List<Runnable> shutdownNow() {
+ return super.shutdownNow();
+ }
+
+ /**
+ * Returns the task queue used by this executor. Each element of
+ * this queue is a {@link ScheduledFuture}, including those
+ * tasks submitted using <tt>execute</tt> which are for scheduling
+ * purposes used as the basis of a zero-delay
+ * <tt>ScheduledFuture</tt>. Iteration over this queue is
+ * <em>not</em> guaranteed to traverse tasks in the order in
+ * which they will execute.
+ *
+ * @return the task queue
+ */
+ public BlockingQueue<Runnable> getQueue() {
+ return super.getQueue();
+ }
+
+ /**
+ * An annoying wrapper class to convince generics compiler to
+ * use a DelayQueue<ScheduledFutureTask> as a BlockingQueue<Runnable>
+ */
+ private static class DelayedWorkQueue
+ extends AbstractCollection<Runnable>
+ implements BlockingQueue<Runnable> {
+
+ private final DelayQueue<ScheduledFutureTask> dq = new DelayQueue<ScheduledFutureTask>();
+ public Runnable poll() { return dq.poll(); }
+ public Runnable peek() { return dq.peek(); }
+ public Runnable take() throws InterruptedException { return dq.take(); }
+ public Runnable poll(long timeout, TimeUnit unit) throws InterruptedException {
+ return dq.poll(timeout, unit);
+ }
+
+ public boolean add(Runnable x) { return dq.add((ScheduledFutureTask)x); }
+ public boolean offer(Runnable x) { return dq.offer((ScheduledFutureTask)x); }
+ public void put(Runnable x) {
+ dq.put((ScheduledFutureTask)x);
+ }
+ public boolean offer(Runnable x, long timeout, TimeUnit unit) {
+ return dq.offer((ScheduledFutureTask)x, timeout, unit);
+ }
+
+ public Runnable remove() { return dq.remove(); }
+ public Runnable element() { return dq.element(); }
+ public void clear() { dq.clear(); }
+ public int drainTo(Collection<? super Runnable> c) { return dq.drainTo(c); }
+ public int drainTo(Collection<? super Runnable> c, int maxElements) {
+ return dq.drainTo(c, maxElements);
+ }
+
+ public int remainingCapacity() { return dq.remainingCapacity(); }
+ public boolean remove(Object x) { return dq.remove(x); }
+ public boolean contains(Object x) { return dq.contains(x); }
+ public int size() { return dq.size(); }
+ public boolean isEmpty() { return dq.isEmpty(); }
+ public Object[] toArray() { return dq.toArray(); }
+ public <T> T[] toArray(T[] array) { return dq.toArray(array); }
+ public Iterator<Runnable> iterator() {
+ return new Iterator<Runnable>() {
+ private Iterator<ScheduledFutureTask> it = dq.iterator();
+ public boolean hasNext() { return it.hasNext(); }
+ public Runnable next() { return it.next(); }
+ public void remove() { it.remove(); }
+ };
+ }
+ }
+}
Propchange: incubator/harmony/enhanced/classlib/trunk/modules/concurrent/src/main/java/java/util/concurrent/ScheduledThreadPoolExecutor.java
------------------------------------------------------------------------------
svn:eol-style = native
Added: incubator/harmony/enhanced/classlib/trunk/modules/concurrent/src/main/java/java/util/concurrent/Semaphore.java
URL: http://svn.apache.org/viewvc/incubator/harmony/enhanced/classlib/trunk/modules/concurrent/src/main/java/java/util/concurrent/Semaphore.java?rev=434296&view=auto
==============================================================================
--- incubator/harmony/enhanced/classlib/trunk/modules/concurrent/src/main/java/java/util/concurrent/Semaphore.java (added)
+++ incubator/harmony/enhanced/classlib/trunk/modules/concurrent/src/main/java/java/util/concurrent/Semaphore.java Wed Aug 23 20:42:25 2006
@@ -0,0 +1,665 @@
+/*
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/licenses/publicdomain
+ */
+
+package java.util.concurrent;
+import java.util.*;
+import java.util.concurrent.locks.*;
+import java.util.concurrent.atomic.*;
+
+/**
+ * A counting semaphore. Conceptually, a semaphore maintains a set of
+ * permits. Each {@link #acquire} blocks if necessary until a permit is
+ * available, and then takes it. Each {@link #release} adds a permit,
+ * potentially releasing a blocking acquirer.
+ * However, no actual permit objects are used; the <tt>Semaphore</tt> just
+ * keeps a count of the number available and acts accordingly.
+ *
+ * <p>Semaphores are often used to restrict the number of threads than can
+ * access some (physical or logical) resource. For example, here is
+ * a class that uses a semaphore to control access to a pool of items:
+ * <pre>
+ * class Pool {
+ * private static final MAX_AVAILABLE = 100;
+ * private final Semaphore available = new Semaphore(MAX_AVAILABLE, true);
+ *
+ * public Object getItem() throws InterruptedException {
+ * available.acquire();
+ * return getNextAvailableItem();
+ * }
+ *
+ * public void putItem(Object x) {
+ * if (markAsUnused(x))
+ * available.release();
+ * }
+ *
+ * // Not a particularly efficient data structure; just for demo
+ *
+ * protected Object[] items = ... whatever kinds of items being managed
+ * protected boolean[] used = new boolean[MAX_AVAILABLE];
+ *
+ * protected synchronized Object getNextAvailableItem() {
+ * for (int i = 0; i < MAX_AVAILABLE; ++i) {
+ * if (!used[i]) {
+ * used[i] = true;
+ * return items[i];
+ * }
+ * }
+ * return null; // not reached
+ * }
+ *
+ * protected synchronized boolean markAsUnused(Object item) {
+ * for (int i = 0; i < MAX_AVAILABLE; ++i) {
+ * if (item == items[i]) {
+ * if (used[i]) {
+ * used[i] = false;
+ * return true;
+ * } else
+ * return false;
+ * }
+ * }
+ * return false;
+ * }
+ *
+ * }
+ * </pre>
+ *
+ * <p>Before obtaining an item each thread must acquire a permit from
+ * the semaphore, guaranteeing that an item is available for use. When
+ * the thread has finished with the item it is returned back to the
+ * pool and a permit is returned to the semaphore, allowing another
+ * thread to acquire that item. Note that no synchronization lock is
+ * held when {@link #acquire} is called as that would prevent an item
+ * from being returned to the pool. The semaphore encapsulates the
+ * synchronization needed to restrict access to the pool, separately
+ * from any synchronization needed to maintain the consistency of the
+ * pool itself.
+ *
+ * <p>A semaphore initialized to one, and which is used such that it
+ * only has at most one permit available, can serve as a mutual
+ * exclusion lock. This is more commonly known as a <em>binary
+ * semaphore</em>, because it only has two states: one permit
+ * available, or zero permits available. When used in this way, the
+ * binary semaphore has the property (unlike many {@link Lock}
+ * implementations), that the "lock" can be released by a
+ * thread other than the owner (as semaphores have no notion of
+ * ownership). This can be useful in some specialized contexts, such
+ * as deadlock recovery.
+ *
+ * <p> The constructor for this class optionally accepts a
+ * <em>fairness</em> parameter. When set false, this class makes no
+ * guarantees about the order in which threads acquire permits. In
+ * particular, <em>barging</em> is permitted, that is, a thread
+ * invoking {@link #acquire} can be allocated a permit ahead of a
+ * thread that has been waiting. When fairness is set true, the
+ * semaphore guarantees that threads invoking any of the {@link
+ * #acquire() acquire} methods are allocated permits in the order in
+ * which their invocation of those methods was processed
+ * (first-in-first-out; FIFO). Note that FIFO ordering necessarily
+ * applies to specific internal points of execution within these
+ * methods. So, it is possible for one thread to invoke
+ * <tt>acquire</tt> before another, but reach the ordering point after
+ * the other, and similarly upon return from the method.
+ *
+ * <p>Generally, semaphores used to control resource access should be
+ * initialized as fair, to ensure that no thread is starved out from
+ * accessing a resource. When using semaphores for other kinds of
+ * synchronization control, the throughput advantages of non-fair
+ * ordering often outweigh fairness considerations.
+ *
+ * <p>This class also provides convenience methods to {@link
+ * #acquire(int) acquire} and {@link #release(int) release} multiple
+ * permits at a time. Beware of the increased risk of indefinite
+ * postponement when these methods are used without fairness set true.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ *
+ */
+
+public class Semaphore implements java.io.Serializable {
+ private static final long serialVersionUID = -3222578661600680210L;
+ /** All mechanics via AbstractQueuedSynchronizer subclass */
+ private final Sync sync;
+
+ /**
+ * Synchronization implementation for semaphore. Uses AQS state
+ * to represent permits. Subclassed into fair and nonfair
+ * versions.
+ */
+ abstract static class Sync extends AbstractQueuedSynchronizer {
+ Sync(int permits) {
+ setState(permits);
+ }
+
+ final int getPermits() {
+ return getState();
+ }
+
+ final int nonfairTryAcquireShared(int acquires) {
+ for (;;) {
+ int available = getState();
+ int remaining = available - acquires;
+ if (remaining < 0 ||
+ compareAndSetState(available, remaining))
+ return remaining;
+ }
+ }
+
+ protected final boolean tryReleaseShared(int releases) {
+ for (;;) {
+ int p = getState();
+ if (compareAndSetState(p, p + releases))
+ return true;
+ }
+ }
+
+ final void reducePermits(int reductions) {
+ for (;;) {
+ int current = getState();
+ int next = current - reductions;
+ if (compareAndSetState(current, next))
+ return;
+ }
+ }
+
+ final int drainPermits() {
+ for (;;) {
+ int current = getState();
+ if (current == 0 || compareAndSetState(current, 0))
+ return current;
+ }
+ }
+ }
+
+ /**
+ * NonFair version
+ */
+ final static class NonfairSync extends Sync {
+ NonfairSync(int permits) {
+ super(permits);
+ }
+
+ protected int tryAcquireShared(int acquires) {
+ return nonfairTryAcquireShared(acquires);
+ }
+ }
+
+ /**
+ * Fair version
+ */
+ final static class FairSync extends Sync {
+ FairSync(int permits) {
+ super(permits);
+ }
+
+ protected int tryAcquireShared(int acquires) {
+ Thread current = Thread.currentThread();
+ for (;;) {
+ Thread first = getFirstQueuedThread();
+ if (first != null && first != current)
+ return -1;
+ int available = getState();
+ int remaining = available - acquires;
+ if (remaining < 0 ||
+ compareAndSetState(available, remaining))
+ return remaining;
+ }
+ }
+ }
+
+ /**
+ * Creates a <tt>Semaphore</tt> with the given number of
+ * permits and nonfair fairness setting.
+ * @param permits the initial number of permits available. This
+ * value may be negative, in which case releases must
+ * occur before any acquires will be granted.
+ */
+ public Semaphore(int permits) {
+ sync = new NonfairSync(permits);
+ }
+
+ /**
+ * Creates a <tt>Semaphore</tt> with the given number of
+ * permits and the given fairness setting.
+ * @param permits the initial number of permits available. This
+ * value may be negative, in which case releases must
+ * occur before any acquires will be granted.
+ * @param fair true if this semaphore will guarantee first-in
+ * first-out granting of permits under contention, else false.
+ */
+ public Semaphore(int permits, boolean fair) {
+ sync = (fair)? new FairSync(permits) : new NonfairSync(permits);
+ }
+
+ /**
+ * Acquires a permit from this semaphore, blocking until one is
+ * available, or the thread is {@link Thread#interrupt interrupted}.
+ *
+ * <p>Acquires a permit, if one is available and returns immediately,
+ * reducing the number of available permits by one.
+ * <p>If no permit is available then the current thread becomes
+ * disabled for thread scheduling purposes and lies dormant until
+ * one of two things happens:
+ * <ul>
+ * <li>Some other thread invokes the {@link #release} method for this
+ * semaphore and the current thread is next to be assigned a permit; or
+ * <li>Some other thread {@link Thread#interrupt interrupts} the current
+ * thread.
+ * </ul>
+ *
+ * <p>If the current thread:
+ * <ul>
+ * <li>has its interrupted status set on entry to this method; or
+ * <li>is {@link Thread#interrupt interrupted} while waiting
+ * for a permit,
+ * </ul>
+ * then {@link InterruptedException} is thrown and the current thread's
+ * interrupted status is cleared.
+ *
+ * @throws InterruptedException if the current thread is interrupted
+ *
+ * @see Thread#interrupt
+ */
+ public void acquire() throws InterruptedException {
+ sync.acquireSharedInterruptibly(1);
+ }
+
+ /**
+ * Acquires a permit from this semaphore, blocking until one is
+ * available.
+ *
+ * <p>Acquires a permit, if one is available and returns immediately,
+ * reducing the number of available permits by one.
+ * <p>If no permit is available then the current thread becomes
+ * disabled for thread scheduling purposes and lies dormant until
+ * some other thread invokes the {@link #release} method for this
+ * semaphore and the current thread is next to be assigned a permit.
+ *
+ * <p>If the current thread
+ * is {@link Thread#interrupt interrupted} while waiting
+ * for a permit then it will continue to wait, but the time at which
+ * the thread is assigned a permit may change compared to the time it
+ * would have received the permit had no interruption occurred. When the
+ * thread does return from this method its interrupt status will be set.
+ *
+ */
+ public void acquireUninterruptibly() {
+ sync.acquireShared(1);
+ }
+
+ /**
+ * Acquires a permit from this semaphore, only if one is available at the
+ * time of invocation.
+ * <p>Acquires a permit, if one is available and returns immediately,
+ * with the value <tt>true</tt>,
+ * reducing the number of available permits by one.
+ *
+ * <p>If no permit is available then this method will return
+ * immediately with the value <tt>false</tt>.
+ *
+ * <p>Even when this semaphore has been set to use a
+ * fair ordering policy, a call to <tt>tryAcquire()</tt> <em>will</em>
+ * immediately acquire a permit if one is available, whether or not
+ * other threads are currently waiting.
+ * This "barging" behavior can be useful in certain
+ * circumstances, even though it breaks fairness. If you want to honor
+ * the fairness setting, then use
+ * {@link #tryAcquire(long, TimeUnit) tryAcquire(0, TimeUnit.SECONDS) }
+ * which is almost equivalent (it also detects interruption).
+ *
+ * @return <tt>true</tt> if a permit was acquired and <tt>false</tt>
+ * otherwise.
+ */
+ public boolean tryAcquire() {
+ return sync.nonfairTryAcquireShared(1) >= 0;
+ }
+
+ /**
+ * Acquires a permit from this semaphore, if one becomes available
+ * within the given waiting time and the
+ * current thread has not been {@link Thread#interrupt interrupted}.
+ * <p>Acquires a permit, if one is available and returns immediately,
+ * with the value <tt>true</tt>,
+ * reducing the number of available permits by one.
+ * <p>If no permit is available then
+ * the current thread becomes disabled for thread scheduling
+ * purposes and lies dormant until one of three things happens:
+ * <ul>
+ * <li>Some other thread invokes the {@link #release} method for this
+ * semaphore and the current thread is next to be assigned a permit; or
+ * <li>Some other thread {@link Thread#interrupt interrupts} the current
+ * thread; or
+ * <li>The specified waiting time elapses.
+ * </ul>
+ * <p>If a permit is acquired then the value <tt>true</tt> is returned.
+ * <p>If the current thread:
+ * <ul>
+ * <li>has its interrupted status set on entry to this method; or
+ * <li>is {@link Thread#interrupt interrupted} while waiting to acquire
+ * a permit,
+ * </ul>
+ * then {@link InterruptedException} is thrown and the current thread's
+ * interrupted status is cleared.
+ * <p>If the specified waiting time elapses then the value <tt>false</tt>
+ * is returned.
+ * If the time is less than or equal to zero, the method will not wait
+ * at all.
+ *
+ * @param timeout the maximum time to wait for a permit
+ * @param unit the time unit of the <tt>timeout</tt> argument.
+ * @return <tt>true</tt> if a permit was acquired and <tt>false</tt>
+ * if the waiting time elapsed before a permit was acquired.
+ *
+ * @throws InterruptedException if the current thread is interrupted
+ *
+ * @see Thread#interrupt
+ *
+ */
+ public boolean tryAcquire(long timeout, TimeUnit unit)
+ throws InterruptedException {
+ return sync.tryAcquireSharedNanos(1, unit.toNanos(timeout));
+ }
+
+ /**
+ * Releases a permit, returning it to the semaphore.
+ * <p>Releases a permit, increasing the number of available permits
+ * by one.
+ * If any threads are blocking trying to acquire a permit, then one
+ * is selected and given the permit that was just released.
+ * That thread is re-enabled for thread scheduling purposes.
+ * <p>There is no requirement that a thread that releases a permit must
+ * have acquired that permit by calling {@link #acquire}.
+ * Correct usage of a semaphore is established by programming convention
+ * in the application.
+ */
+ public void release() {
+ sync.releaseShared(1);
+ }
+
+ /**
+ * Acquires the given number of permits from this semaphore,
+ * blocking until all are available,
+ * or the thread is {@link Thread#interrupt interrupted}.
+ *
+ * <p>Acquires the given number of permits, if they are available,
+ * and returns immediately,
+ * reducing the number of available permits by the given amount.
+ *
+ * <p>If insufficient permits are available then the current thread becomes
+ * disabled for thread scheduling purposes and lies dormant until
+ * one of two things happens:
+ * <ul>
+ * <li>Some other thread invokes one of the {@link #release() release}
+ * methods for this semaphore, the current thread is next to be assigned
+ * permits and the number of available permits satisfies this request; or
+ * <li>Some other thread {@link Thread#interrupt interrupts} the current
+ * thread.
+ * </ul>
+ *
+ * <p>If the current thread:
+ * <ul>
+ * <li>has its interrupted status set on entry to this method; or
+ * <li>is {@link Thread#interrupt interrupted} while waiting
+ * for a permit,
+ * </ul>
+ * then {@link InterruptedException} is thrown and the current thread's
+ * interrupted status is cleared.
+ * Any permits that were to be assigned to this thread are instead
+ * assigned to the next waiting thread(s), as if
+ * they had been made available by a call to {@link #release()}.
+ *
+ * @param permits the number of permits to acquire
+ *
+ * @throws InterruptedException if the current thread is interrupted
+ * @throws IllegalArgumentException if permits less than zero.
+ *
+ * @see Thread#interrupt
+ */
+ public void acquire(int permits) throws InterruptedException {
+ if (permits < 0) throw new IllegalArgumentException();
+ sync.acquireSharedInterruptibly(permits);
+ }
+
+ /**
+ * Acquires the given number of permits from this semaphore,
+ * blocking until all are available.
+ *
+ * <p>Acquires the given number of permits, if they are available,
+ * and returns immediately,
+ * reducing the number of available permits by the given amount.
+ *
+ * <p>If insufficient permits are available then the current thread becomes
+ * disabled for thread scheduling purposes and lies dormant until
+ * some other thread invokes one of the {@link #release() release}
+ * methods for this semaphore, the current thread is next to be assigned
+ * permits and the number of available permits satisfies this request.
+ *
+ * <p>If the current thread
+ * is {@link Thread#interrupt interrupted} while waiting
+ * for permits then it will continue to wait and its position in the
+ * queue is not affected. When the
+ * thread does return from this method its interrupt status will be set.
+ *
+ * @param permits the number of permits to acquire
+ * @throws IllegalArgumentException if permits less than zero.
+ *
+ */
+ public void acquireUninterruptibly(int permits) {
+ if (permits < 0) throw new IllegalArgumentException();
+ sync.acquireShared(permits);
+ }
+
+ /**
+ * Acquires the given number of permits from this semaphore, only
+ * if all are available at the time of invocation.
+ *
+ * <p>Acquires the given number of permits, if they are available, and
+ * returns immediately, with the value <tt>true</tt>,
+ * reducing the number of available permits by the given amount.
+ *
+ * <p>If insufficient permits are available then this method will return
+ * immediately with the value <tt>false</tt> and the number of available
+ * permits is unchanged.
+ *
+ * <p>Even when this semaphore has been set to use a fair ordering
+ * policy, a call to <tt>tryAcquire</tt> <em>will</em>
+ * immediately acquire a permit if one is available, whether or
+ * not other threads are currently waiting. This
+ * "barging" behavior can be useful in certain
+ * circumstances, even though it breaks fairness. If you want to
+ * honor the fairness setting, then use {@link #tryAcquire(int,
+ * long, TimeUnit) tryAcquire(permits, 0, TimeUnit.SECONDS) }
+ * which is almost equivalent (it also detects interruption).
+ *
+ * @param permits the number of permits to acquire
+ *
+ * @return <tt>true</tt> if the permits were acquired and <tt>false</tt>
+ * otherwise.
+ * @throws IllegalArgumentException if permits less than zero.
+ */
+ public boolean tryAcquire(int permits) {
+ if (permits < 0) throw new IllegalArgumentException();
+ return sync.nonfairTryAcquireShared(permits) >= 0;
+ }
+
+ /**
+ * Acquires the given number of permits from this semaphore, if all
+ * become available within the given waiting time and the
+ * current thread has not been {@link Thread#interrupt interrupted}.
+ * <p>Acquires the given number of permits, if they are available and
+ * returns immediately, with the value <tt>true</tt>,
+ * reducing the number of available permits by the given amount.
+ * <p>If insufficient permits are available then
+ * the current thread becomes disabled for thread scheduling
+ * purposes and lies dormant until one of three things happens:
+ * <ul>
+ * <li>Some other thread invokes one of the {@link #release() release}
+ * methods for this semaphore, the current thread is next to be assigned
+ * permits and the number of available permits satisfies this request; or
+ * <li>Some other thread {@link Thread#interrupt interrupts} the current
+ * thread; or
+ * <li>The specified waiting time elapses.
+ * </ul>
+ * <p>If the permits are acquired then the value <tt>true</tt> is returned.
+ * <p>If the current thread:
+ * <ul>
+ * <li>has its interrupted status set on entry to this method; or
+ * <li>is {@link Thread#interrupt interrupted} while waiting to acquire
+ * the permits,
+ * </ul>
+ * then {@link InterruptedException} is thrown and the current thread's
+ * interrupted status is cleared.
+ * Any permits that were to be assigned to this thread, are instead
+ * assigned to the next waiting thread(s), as if
+ * they had been made available by a call to {@link #release()}.
+ *
+ * <p>If the specified waiting time elapses then the value <tt>false</tt>
+ * is returned.
+ * If the time is
+ * less than or equal to zero, the method will not wait at all.
+ * Any permits that were to be assigned to this thread, are instead
+ * assigned to the next waiting thread(s), as if
+ * they had been made available by a call to {@link #release()}.
+ *
+ * @param permits the number of permits to acquire
+ * @param timeout the maximum time to wait for the permits
+ * @param unit the time unit of the <tt>timeout</tt> argument.
+ * @return <tt>true</tt> if all permits were acquired and <tt>false</tt>
+ * if the waiting time elapsed before all permits were acquired.
+ *
+ * @throws InterruptedException if the current thread is interrupted
+ * @throws IllegalArgumentException if permits less than zero.
+ *
+ * @see Thread#interrupt
+ *
+ */
+ public boolean tryAcquire(int permits, long timeout, TimeUnit unit)
+ throws InterruptedException {
+ if (permits < 0) throw new IllegalArgumentException();
+ return sync.tryAcquireSharedNanos(permits, unit.toNanos(timeout));
+ }
+
+ /**
+ * Releases the given number of permits, returning them to the semaphore.
+ * <p>Releases the given number of permits, increasing the number of
+ * available permits by that amount.
+ * If any threads are blocking trying to acquire permits, then the
+ * one that has been waiting the longest
+ * is selected and given the permits that were just released.
+ * If the number of available permits satisfies that thread's request
+ * then that thread is re-enabled for thread scheduling purposes; otherwise
+ * the thread continues to wait. If there are still permits available
+ * after the first thread's request has been satisfied, then those permits
+ * are assigned to the next waiting thread. If it is satisfied then it is
+ * re-enabled for thread scheduling purposes. This continues until there
+ * are insufficient permits to satisfy the next waiting thread, or there
+ * are no more waiting threads.
+ *
+ * <p>There is no requirement that a thread that releases a permit must
+ * have acquired that permit by calling {@link Semaphore#acquire acquire}.
+ * Correct usage of a semaphore is established by programming convention
+ * in the application.
+ *
+ * @param permits the number of permits to release
+ * @throws IllegalArgumentException if permits less than zero.
+ */
+ public void release(int permits) {
+ if (permits < 0) throw new IllegalArgumentException();
+ sync.releaseShared(permits);
+ }
+
+ /**
+ * Returns the current number of permits available in this semaphore.
+ * <p>This method is typically used for debugging and testing purposes.
+ * @return the number of permits available in this semaphore.
+ */
+ public int availablePermits() {
+ return sync.getPermits();
+ }
+
+ /**
+ * Acquire and return all permits that are immediately available.
+ * @return the number of permits
+ */
+ public int drainPermits() {
+ return sync.drainPermits();
+ }
+
+ /**
+ * Shrinks the number of available permits by the indicated
+ * reduction. This method can be useful in subclasses that use
+ * semaphores to track resources that become unavailable. This
+ * method differs from <tt>acquire</tt> in that it does not block
+ * waiting for permits to become available.
+ * @param reduction the number of permits to remove
+ * @throws IllegalArgumentException if reduction is negative
+ */
+ protected void reducePermits(int reduction) {
+ if (reduction < 0) throw new IllegalArgumentException();
+ sync.reducePermits(reduction);
+ }
+
+ /**
+ * Returns true if this semaphore has fairness set true.
+ * @return true if this semaphore has fairness set true.
+ */
+ public boolean isFair() {
+ return sync instanceof FairSync;
+ }
+
+ /**
+ * Queries whether any threads are waiting to acquire. Note that
+ * because cancellations may occur at any time, a <tt>true</tt>
+ * return does not guarantee that any other thread will ever
+ * acquire. This method is designed primarily for use in
+ * monitoring of the system state.
+ *
+ * @return true if there may be other threads waiting to acquire
+ * the lock.
+ */
+ public final boolean hasQueuedThreads() {
+ return sync.hasQueuedThreads();
+ }
+
+ /**
+ * Returns an estimate of the number of threads waiting to
+ * acquire. The value is only an estimate because the number of
+ * threads may change dynamically while this method traverses
+ * internal data structures. This method is designed for use in
+ * monitoring of the system state, not for synchronization
+ * control.
+ * @return the estimated number of threads waiting for this lock
+ */
+ public final int getQueueLength() {
+ return sync.getQueueLength();
+ }
+
+ /**
+ * Returns a collection containing threads that may be waiting to
+ * acquire. Because the actual set of threads may change
+ * dynamically while constructing this result, the returned
+ * collection is only a best-effort estimate. The elements of the
+ * returned collection are in no particular order. This method is
+ * designed to facilitate construction of subclasses that provide
+ * more extensive monitoring facilities.
+ * @return the collection of threads
+ */
+ protected Collection<Thread> getQueuedThreads() {
+ return sync.getQueuedThreads();
+ }
+
+ /**
+ * Returns a string identifying this semaphore, as well as its state.
+ * The state, in brackets, includes the String
+ * "Permits =" followed by the number of permits.
+ * @return a string identifying this semaphore, as well as its
+ * state
+ */
+ public String toString() {
+ return super.toString() + "[Permits = " + sync.getPermits() + "]";
+ }
+
+}
Propchange: incubator/harmony/enhanced/classlib/trunk/modules/concurrent/src/main/java/java/util/concurrent/Semaphore.java
------------------------------------------------------------------------------
svn:eol-style = native
Added: incubator/harmony/enhanced/classlib/trunk/modules/concurrent/src/main/java/java/util/concurrent/SynchronousQueue.java
URL: http://svn.apache.org/viewvc/incubator/harmony/enhanced/classlib/trunk/modules/concurrent/src/main/java/java/util/concurrent/SynchronousQueue.java?rev=434296&view=auto
==============================================================================
--- incubator/harmony/enhanced/classlib/trunk/modules/concurrent/src/main/java/java/util/concurrent/SynchronousQueue.java (added)
+++ incubator/harmony/enhanced/classlib/trunk/modules/concurrent/src/main/java/java/util/concurrent/SynchronousQueue.java Wed Aug 23 20:42:25 2006
@@ -0,0 +1,685 @@
+/*
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/licenses/publicdomain
+ */
+
+package java.util.concurrent;
+import java.util.concurrent.locks.*;
+import java.util.*;
+
+/**
+ * A {@linkplain BlockingQueue blocking queue} in which each
+ * <tt>put</tt> must wait for a <tt>take</tt>, and vice versa. A
+ * synchronous queue does not have any internal capacity, not even a
+ * capacity of one. You cannot <tt>peek</tt> at a synchronous queue
+ * because an element is only present when you try to take it; you
+ * cannot add an element (using any method) unless another thread is
+ * trying to remove it; you cannot iterate as there is nothing to
+ * iterate. The <em>head</em> of the queue is the element that the
+ * first queued thread is trying to add to the queue; if there are no
+ * queued threads then no element is being added and the head is
+ * <tt>null</tt>. For purposes of other <tt>Collection</tt> methods
+ * (for example <tt>contains</tt>), a <tt>SynchronousQueue</tt> acts
+ * as an empty collection. This queue does not permit <tt>null</tt>
+ * elements.
+ *
+ * <p>Synchronous queues are similar to rendezvous channels used in
+ * CSP and Ada. They are well suited for handoff designs, in which an
+ * object running in one thread must sync up with an object running
+ * in another thread in order to hand it some information, event, or
+ * task.
+ *
+ * <p> This class supports an optional fairness policy for ordering
+ * waiting producer and consumer threads. By default, this ordering
+ * is not guaranteed. However, a queue constructed with fairness set
+ * to <tt>true</tt> grants threads access in FIFO order. Fairness
+ * generally decreases throughput but reduces variability and avoids
+ * starvation.
+ *
+ * <p>This class implements all of the <em>optional</em> methods
+ * of the {@link Collection} and {@link Iterator} interfaces.
+ *
+ * <p>This class is a member of the
+ * <a href="{@docRoot}/../guide/collections/index.html">
+ * Java Collections Framework</a>.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ * @param <E> the type of elements held in this collection
+ */
+public class SynchronousQueue<E> extends AbstractQueue<E>
+ implements BlockingQueue<E>, java.io.Serializable {
+ private static final long serialVersionUID = -3223113410248163686L;
+
+ /*
+ This implementation divides actions into two cases for puts:
+
+ * An arriving producer that does not already have a waiting consumer
+ creates a node holding item, and then waits for a consumer to take it.
+ * An arriving producer that does already have a waiting consumer fills
+ the slot node created by the consumer, and notifies it to continue.
+
+ And symmetrically, two for takes:
+
+ * An arriving consumer that does not already have a waiting producer
+ creates an empty slot node, and then waits for a producer to fill it.
+ * An arriving consumer that does already have a waiting producer takes
+ item from the node created by the producer, and notifies it to continue.
+
+ When a put or take waiting for the actions of its counterpart
+ aborts due to interruption or timeout, it marks the node
+ it created as "CANCELLED", which causes its counterpart to retry
+ the entire put or take sequence.
+
+ This requires keeping two simple queues, waitingProducers and
+ waitingConsumers. Each of these can be FIFO (preserves fairness)
+ or LIFO (improves throughput).
+ */
+
+ /** Lock protecting both wait queues */
+ private final ReentrantLock qlock;
+ /** Queue holding waiting puts */
+ private final WaitQueue waitingProducers;
+ /** Queue holding waiting takes */
+ private final WaitQueue waitingConsumers;
+
+ /**
+ * Creates a <tt>SynchronousQueue</tt> with nonfair access policy.
+ */
+ public SynchronousQueue() {
+ this(false);
+ }
+
+ /**
+ * Creates a <tt>SynchronousQueue</tt> with specified fairness policy.
+ * @param fair if true, threads contend in FIFO order for access;
+ * otherwise the order is unspecified.
+ */
+ public SynchronousQueue(boolean fair) {
+ if (fair) {
+ qlock = new ReentrantLock(true);
+ waitingProducers = new FifoWaitQueue();
+ waitingConsumers = new FifoWaitQueue();
+ }
+ else {
+ qlock = new ReentrantLock();
+ waitingProducers = new LifoWaitQueue();
+ waitingConsumers = new LifoWaitQueue();
+ }
+ }
+
+ /**
+ * Queue to hold waiting puts/takes; specialized to Fifo/Lifo below.
+ * These queues have all transient fields, but are serializable
+ * in order to recover fairness settings when deserialized.
+ */
+ static abstract class WaitQueue implements java.io.Serializable {
+ /** Create, add, and return node for x */
+ abstract Node enq(Object x);
+ /** Remove and return node, or null if empty */
+ abstract Node deq();
+ }
+
+ /**
+ * FIFO queue to hold waiting puts/takes.
+ */
+ static final class FifoWaitQueue extends WaitQueue implements java.io.Serializable {
+ private static final long serialVersionUID = -3623113410248163686L;
+ private transient Node head;
+ private transient Node last;
+
+ Node enq(Object x) {
+ Node p = new Node(x);
+ if (last == null)
+ last = head = p;
+ else
+ last = last.next = p;
+ return p;
+ }
+
+ Node deq() {
+ Node p = head;
+ if (p != null) {
+ if ((head = p.next) == null)
+ last = null;
+ p.next = null;
+ }
+ return p;
+ }
+ }
+
+ /**
+ * LIFO queue to hold waiting puts/takes.
+ */
+ static final class LifoWaitQueue extends WaitQueue implements java.io.Serializable {
+ private static final long serialVersionUID = -3633113410248163686L;
+ private transient Node head;
+
+ Node enq(Object x) {
+ return head = new Node(x, head);
+ }
+
+ Node deq() {
+ Node p = head;
+ if (p != null) {
+ head = p.next;
+ p.next = null;
+ }
+ return p;
+ }
+ }
+
+ /**
+ * Nodes each maintain an item and handle waits and signals for
+ * getting and setting it. The class extends
+ * AbstractQueuedSynchronizer to manage blocking, using AQS state
+ * 0 for waiting, 1 for ack, -1 for cancelled.
+ */
+ static final class Node extends AbstractQueuedSynchronizer {
+ /** Synchronization state value representing that node acked */
+ private static final int ACK = 1;
+ /** Synchronization state value representing that node cancelled */
+ private static final int CANCEL = -1;
+
+ /** The item being transferred */
+ Object item;
+ /** Next node in wait queue */
+ Node next;
+
+ /** Creates a node with initial item */
+ Node(Object x) { item = x; }
+
+ /** Creates a node with initial item and next */
+ Node(Object x, Node n) { item = x; next = n; }
+
+ /**
+ * Implements AQS base acquire to succeed if not in WAITING state
+ */
+ protected boolean tryAcquire(int ignore) {
+ return getState() != 0;
+ }
+
+ /**
+ * Implements AQS base release to signal if state changed
+ */
+ protected boolean tryRelease(int newState) {
+ return compareAndSetState(0, newState);
+ }
+
+ /**
+ * Takes item and nulls out field (for sake of GC)
+ */
+ private Object extract() {
+ Object x = item;
+ item = null;
+ return x;
+ }
+
+ /**
+ * Tries to cancel on interrupt; if so rethrowing,
+ * else setting interrupt state
+ */
+ private void checkCancellationOnInterrupt(InterruptedException ie)
+ throws InterruptedException {
+ if (release(CANCEL))
+ throw ie;
+ Thread.currentThread().interrupt();
+ }
+
+ /**
+ * Fills in the slot created by the consumer and signal consumer to
+ * continue.
+ */
+ boolean setItem(Object x) {
+ item = x; // can place in slot even if cancelled
+ return release(ACK);
+ }
+
+ /**
+ * Removes item from slot created by producer and signal producer
+ * to continue.
+ */
+ Object getItem() {
+ return (release(ACK))? extract() : null;
+ }
+
+ /**
+ * Waits for a consumer to take item placed by producer.
+ */
+ void waitForTake() throws InterruptedException {
+ try {
+ acquireInterruptibly(0);
+ } catch (InterruptedException ie) {
+ checkCancellationOnInterrupt(ie);
+ }
+ }
+
+ /**
+ * Waits for a producer to put item placed by consumer.
+ */
+ Object waitForPut() throws InterruptedException {
+ try {
+ acquireInterruptibly(0);
+ } catch (InterruptedException ie) {
+ checkCancellationOnInterrupt(ie);
+ }
+ return extract();
+ }
+
+ /**
+ * Waits for a consumer to take item placed by producer or time out.
+ */
+ boolean waitForTake(long nanos) throws InterruptedException {
+ try {
+ if (!tryAcquireNanos(0, nanos) &&
+ release(CANCEL))
+ return false;
+ } catch (InterruptedException ie) {
+ checkCancellationOnInterrupt(ie);
+ }
+ return true;
+ }
+
+ /**
+ * Waits for a producer to put item placed by consumer, or time out.
+ */
+ Object waitForPut(long nanos) throws InterruptedException {
+ try {
+ if (!tryAcquireNanos(0, nanos) &&
+ release(CANCEL))
+ return null;
+ } catch (InterruptedException ie) {
+ checkCancellationOnInterrupt(ie);
+ }
+ return extract();
+ }
+ }
+
+ /**
+ * Adds the specified element to this queue, waiting if necessary for
+ * another thread to receive it.
+ * @param o the element to add
+ * @throws InterruptedException if interrupted while waiting.
+ * @throws NullPointerException if the specified element is <tt>null</tt>.
+ */
+ public void put(E o) throws InterruptedException {
+ if (o == null) throw new NullPointerException();
+ final ReentrantLock qlock = this.qlock;
+
+ for (;;) {
+ Node node;
+ boolean mustWait;
+ if (Thread.interrupted()) throw new InterruptedException();
+ qlock.lock();
+ try {
+ node = waitingConsumers.deq();
+ if ( (mustWait = (node == null)) )
+ node = waitingProducers.enq(o);
+ } finally {
+ qlock.unlock();
+ }
+
+ if (mustWait) {
+ node.waitForTake();
+ return;
+ }
+
+ else if (node.setItem(o))
+ return;
+
+ // else consumer cancelled, so retry
+ }
+ }
+
+ /**
+ * Inserts the specified element into this queue, waiting if necessary
+ * up to the specified wait time for another thread to receive it.
+ * @param o the element to add
+ * @param timeout how long to wait before giving up, in units of
+ * <tt>unit</tt>
+ * @param unit a <tt>TimeUnit</tt> determining how to interpret the
+ * <tt>timeout</tt> parameter
+ * @return <tt>true</tt> if successful, or <tt>false</tt> if
+ * the specified waiting time elapses before a consumer appears.
+ * @throws InterruptedException if interrupted while waiting.
+ * @throws NullPointerException if the specified element is <tt>null</tt>.
+ */
+ public boolean offer(E o, long timeout, TimeUnit unit) throws InterruptedException {
+ if (o == null) throw new NullPointerException();
+ long nanos = unit.toNanos(timeout);
+ final ReentrantLock qlock = this.qlock;
+ for (;;) {
+ Node node;
+ boolean mustWait;
+ if (Thread.interrupted()) throw new InterruptedException();
+ qlock.lock();
+ try {
+ node = waitingConsumers.deq();
+ if ( (mustWait = (node == null)) )
+ node = waitingProducers.enq(o);
+ } finally {
+ qlock.unlock();
+ }
+
+ if (mustWait)
+ return node.waitForTake(nanos);
+
+ else if (node.setItem(o))
+ return true;
+
+ // else consumer cancelled, so retry
+ }
+ }
+
+ /**
+ * Retrieves and removes the head of this queue, waiting if necessary
+ * for another thread to insert it.
+ * @throws InterruptedException if interrupted while waiting.
+ * @return the head of this queue
+ */
+ public E take() throws InterruptedException {
+ final ReentrantLock qlock = this.qlock;
+ for (;;) {
+ Node node;
+ boolean mustWait;
+
+ if (Thread.interrupted()) throw new InterruptedException();
+ qlock.lock();
+ try {
+ node = waitingProducers.deq();
+ if ( (mustWait = (node == null)) )
+ node = waitingConsumers.enq(null);
+ } finally {
+ qlock.unlock();
+ }
+
+ if (mustWait) {
+ Object x = node.waitForPut();
+ return (E)x;
+ }
+ else {
+ Object x = node.getItem();
+ if (x != null)
+ return (E)x;
+ // else cancelled, so retry
+ }
+ }
+ }
+
+ /**
+ * Retrieves and removes the head of this queue, waiting
+ * if necessary up to the specified wait time, for another thread
+ * to insert it.
+ * @param timeout how long to wait before giving up, in units of
+ * <tt>unit</tt>
+ * @param unit a <tt>TimeUnit</tt> determining how to interpret the
+ * <tt>timeout</tt> parameter
+ * @return the head of this queue, or <tt>null</tt> if the
+ * specified waiting time elapses before an element is present.
+ * @throws InterruptedException if interrupted while waiting.
+ */
+ public E poll(long timeout, TimeUnit unit) throws InterruptedException {
+ long nanos = unit.toNanos(timeout);
+ final ReentrantLock qlock = this.qlock;
+
+ for (;;) {
+ Node node;
+ boolean mustWait;
+
+ if (Thread.interrupted()) throw new InterruptedException();
+ qlock.lock();
+ try {
+ node = waitingProducers.deq();
+ if ( (mustWait = (node == null)) )
+ node = waitingConsumers.enq(null);
+ } finally {
+ qlock.unlock();
+ }
+
+ if (mustWait) {
+ Object x = node.waitForPut(nanos);
+ return (E)x;
+ }
+ else {
+ Object x = node.getItem();
+ if (x != null)
+ return (E)x;
+ // else cancelled, so retry
+ }
+ }
+ }
+
+ // Untimed nonblocking versions
+
+ /**
+ * Inserts the specified element into this queue, if another thread is
+ * waiting to receive it.
+ *
+ * @param o the element to add.
+ * @return <tt>true</tt> if it was possible to add the element to
+ * this queue, else <tt>false</tt>
+ * @throws NullPointerException if the specified element is <tt>null</tt>
+ */
+ public boolean offer(E o) {
+ if (o == null) throw new NullPointerException();
+ final ReentrantLock qlock = this.qlock;
+
+ for (;;) {
+ Node node;
+ qlock.lock();
+ try {
+ node = waitingConsumers.deq();
+ } finally {
+ qlock.unlock();
+ }
+ if (node == null)
+ return false;
+
+ else if (node.setItem(o))
+ return true;
+ // else retry
+ }
+ }
+
+ /**
+ * Retrieves and removes the head of this queue, if another thread
+ * is currently making an element available.
+ *
+ * @return the head of this queue, or <tt>null</tt> if no
+ * element is available.
+ */
+ public E poll() {
+ final ReentrantLock qlock = this.qlock;
+ for (;;) {
+ Node node;
+ qlock.lock();
+ try {
+ node = waitingProducers.deq();
+ } finally {
+ qlock.unlock();
+ }
+ if (node == null)
+ return null;
+
+ else {
+ Object x = node.getItem();
+ if (x != null)
+ return (E)x;
+ // else retry
+ }
+ }
+ }
+
+ /**
+ * Always returns <tt>true</tt>.
+ * A <tt>SynchronousQueue</tt> has no internal capacity.
+ * @return <tt>true</tt>
+ */
+ public boolean isEmpty() {
+ return true;
+ }
+
+ /**
+ * Always returns zero.
+ * A <tt>SynchronousQueue</tt> has no internal capacity.
+ * @return zero.
+ */
+ public int size() {
+ return 0;
+ }
+
+ /**
+ * Always returns zero.
+ * A <tt>SynchronousQueue</tt> has no internal capacity.
+ * @return zero.
+ */
+ public int remainingCapacity() {
+ return 0;
+ }
+
+ /**
+ * Does nothing.
+ * A <tt>SynchronousQueue</tt> has no internal capacity.
+ */
+ public void clear() {}
+
+ /**
+ * Always returns <tt>false</tt>.
+ * A <tt>SynchronousQueue</tt> has no internal capacity.
+ * @param o the element
+ * @return <tt>false</tt>
+ */
+ public boolean contains(Object o) {
+ return false;
+ }
+
+ /**
+ * Always returns <tt>false</tt>.
+ * A <tt>SynchronousQueue</tt> has no internal capacity.
+ *
+ * @param o the element to remove
+ * @return <tt>false</tt>
+ */
+ public boolean remove(Object o) {
+ return false;
+ }
+
+ /**
+ * Returns <tt>false</tt> unless given collection is empty.
+ * A <tt>SynchronousQueue</tt> has no internal capacity.
+ * @param c the collection
+ * @return <tt>false</tt> unless given collection is empty
+ */
+ public boolean containsAll(Collection<?> c) {
+ return c.isEmpty();
+ }
+
+ /**
+ * Always returns <tt>false</tt>.
+ * A <tt>SynchronousQueue</tt> has no internal capacity.
+ * @param c the collection
+ * @return <tt>false</tt>
+ */
+ public boolean removeAll(Collection<?> c) {
+ return false;
+ }
+
+ /**
+ * Always returns <tt>false</tt>.
+ * A <tt>SynchronousQueue</tt> has no internal capacity.
+ * @param c the collection
+ * @return <tt>false</tt>
+ */
+ public boolean retainAll(Collection<?> c) {
+ return false;
+ }
+
+ /**
+ * Always returns <tt>null</tt>.
+ * A <tt>SynchronousQueue</tt> does not return elements
+ * unless actively waited on.
+ * @return <tt>null</tt>
+ */
+ public E peek() {
+ return null;
+ }
+
+
+ static class EmptyIterator<E> implements Iterator<E> {
+ public boolean hasNext() {
+ return false;
+ }
+ public E next() {
+ throw new NoSuchElementException();
+ }
+ public void remove() {
+ throw new IllegalStateException();
+ }
+ }
+
+ /**
+ * Returns an empty iterator in which <tt>hasNext</tt> always returns
+ * <tt>false</tt>.
+ *
+ * @return an empty iterator
+ */
+ public Iterator<E> iterator() {
+ return new EmptyIterator<E>();
+ }
+
+
+ /**
+ * Returns a zero-length array.
+ * @return a zero-length array
+ */
+ public Object[] toArray() {
+ return new Object[0];
+ }
+
+ /**
+ * Sets the zeroeth element of the specified array to <tt>null</tt>
+ * (if the array has non-zero length) and returns it.
+ * @param a the array
+ * @return the specified array
+ */
+ public <T> T[] toArray(T[] a) {
+ if (a.length > 0)
+ a[0] = null;
+ return a;
+ }
+
+
+ public int drainTo(Collection<? super E> c) {
+ if (c == null)
+ throw new NullPointerException();
+ if (c == this)
+ throw new IllegalArgumentException();
+ int n = 0;
+ E e;
+ while ( (e = poll()) != null) {
+ c.add(e);
+ ++n;
+ }
+ return n;
+ }
+
+ public int drainTo(Collection<? super E> c, int maxElements) {
+ if (c == null)
+ throw new NullPointerException();
+ if (c == this)
+ throw new IllegalArgumentException();
+ int n = 0;
+ E e;
+ while (n < maxElements && (e = poll()) != null) {
+ c.add(e);
+ ++n;
+ }
+ return n;
+ }
+}
+
+
+
+
+
Propchange: incubator/harmony/enhanced/classlib/trunk/modules/concurrent/src/main/java/java/util/concurrent/SynchronousQueue.java
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Added: incubator/harmony/enhanced/classlib/trunk/modules/concurrent/src/main/java/java/util/concurrent/ThreadFactory.java
URL: http://svn.apache.org/viewvc/incubator/harmony/enhanced/classlib/trunk/modules/concurrent/src/main/java/java/util/concurrent/ThreadFactory.java?rev=434296&view=auto
==============================================================================
--- incubator/harmony/enhanced/classlib/trunk/modules/concurrent/src/main/java/java/util/concurrent/ThreadFactory.java (added)
+++ incubator/harmony/enhanced/classlib/trunk/modules/concurrent/src/main/java/java/util/concurrent/ThreadFactory.java Wed Aug 23 20:42:25 2006
@@ -0,0 +1,40 @@
+/*
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/licenses/publicdomain
+ */
+
+package java.util.concurrent;
+
+/**
+ * An object that creates new threads on demand. Using thread factories
+ * removes hardwiring of calls to {@link Thread#Thread(Runnable) new Thread},
+ * enabling applications to use special thread subclasses, priorities, etc.
+ *
+ * <p>
+ * The simplest implementation of this interface is just:
+ * <pre>
+ * class SimpleThreadFactory implements ThreadFactory {
+ * public Thread newThread(Runnable r) {
+ * return new Thread(r);
+ * }
+ * }
+ * </pre>
+ *
+ * The {@link Executors#defaultThreadFactory} method provides a more
+ * useful simple implementation, that sets the created thread context
+ * to known values before returning it.
+ * @since 1.5
+ * @author Doug Lea
+ */
+public interface ThreadFactory {
+
+ /**
+ * Constructs a new <tt>Thread</tt>. Implementations may also initialize
+ * priority, name, daemon status, <tt>ThreadGroup</tt>, etc.
+ *
+ * @param r a runnable to be executed by new thread instance
+ * @return constructed thread
+ */
+ Thread newThread(Runnable r);
+}
Propchange: incubator/harmony/enhanced/classlib/trunk/modules/concurrent/src/main/java/java/util/concurrent/ThreadFactory.java
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