Class Queues

java.lang.Object
com.google.common.collect.Queues
@GwtCompatible(emulated=true) public final class Queues extends Object
Static utility methods pertaining to Queue and Deque instances. Also see this class's counterparts Lists, Sets, and Maps.
Since:
11.0
Author:
Kurt Alfred Kluever

  • Method Details

    • newArrayBlockingQueue

      @GwtIncompatible public static <E> ArrayBlockingQueue<E> newArrayBlockingQueue(int capacity)
      Creates an empty ArrayBlockingQueue with the given (fixed) capacity and nonfair access policy.

    • newArrayDeque

      public static <E> ArrayDeque<E> newArrayDeque()
      Creates an empty ArrayDeque.
      Since:
      12.0

    • newArrayDeque

      public static <E> ArrayDeque<E> newArrayDeque(Iterable<? extends E> elements)
      Creates an ArrayDeque containing the elements of the specified iterable, in the order they are returned by the iterable's iterator.
      Since:
      12.0

    • newConcurrentLinkedQueue

      @GwtIncompatible public static <E> ConcurrentLinkedQueue<E> newConcurrentLinkedQueue()
      Creates an empty ConcurrentLinkedQueue.

    • newConcurrentLinkedQueue

      @GwtIncompatible public static <E> ConcurrentLinkedQueue<E> newConcurrentLinkedQueue(Iterable<? extends E> elements)
      Creates a ConcurrentLinkedQueue containing the elements of the specified iterable, in the order they are returned by the iterable's iterator.

    • newLinkedBlockingDeque

      @GwtIncompatible public static <E> LinkedBlockingDeque<E> newLinkedBlockingDeque()
      Creates an empty LinkedBlockingDeque with a capacity of Integer.MAX_VALUE.
      Since:
      12.0

    • newLinkedBlockingDeque

      @GwtIncompatible public static <E> LinkedBlockingDeque<E> newLinkedBlockingDeque(int capacity)
      Creates an empty LinkedBlockingDeque with the given (fixed) capacity.
      Throws:
      IllegalArgumentException - if capacity is less than 1
      Since:
      12.0

    • newLinkedBlockingDeque

      @GwtIncompatible public static <E> LinkedBlockingDeque<E> newLinkedBlockingDeque(Iterable<? extends E> elements)
      Creates a LinkedBlockingDeque with a capacity of Integer.MAX_VALUE, containing the elements of the specified iterable, in the order they are returned by the iterable's iterator.
      Since:
      12.0

    • newLinkedBlockingQueue

      @GwtIncompatible public static <E> LinkedBlockingQueue<E> newLinkedBlockingQueue()
      Creates an empty LinkedBlockingQueue with a capacity of Integer.MAX_VALUE.

    • newLinkedBlockingQueue

      @GwtIncompatible public static <E> LinkedBlockingQueue<E> newLinkedBlockingQueue(int capacity)
      Creates an empty LinkedBlockingQueue with the given (fixed) capacity.
      Throws:
      IllegalArgumentException - if capacity is less than 1

    • newLinkedBlockingQueue

      @GwtIncompatible public static <E> LinkedBlockingQueue<E> newLinkedBlockingQueue(Iterable<? extends E> elements)
      Creates a LinkedBlockingQueue with a capacity of Integer.MAX_VALUE, containing the elements of the specified iterable, in the order they are returned by the iterable's iterator.
      Parameters:
      elements - the elements that the queue should contain, in order
      Returns:
      a new LinkedBlockingQueue containing those elements

    • newPriorityBlockingQueue

      @GwtIncompatible public static <E extends Comparable> PriorityBlockingQueue<E> newPriorityBlockingQueue()
      Creates an empty PriorityBlockingQueue with the ordering given by its elements' natural ordering.
      Since:
      11.0 (but the bound of E was changed from Object to Comparable in 15.0)

    • newPriorityBlockingQueue

      @GwtIncompatible public static <E extends Comparable> PriorityBlockingQueue<E> newPriorityBlockingQueue(Iterable<? extends E> elements)
      Creates a PriorityBlockingQueue containing the given elements.

      Note: If the specified iterable is a SortedSet or a PriorityQueue, this priority queue will be ordered according to the same ordering.

      Since:
      11.0 (but the bound of E was changed from Object to Comparable in 15.0)

    • newPriorityQueue

      public static <E extends Comparable> PriorityQueue<E> newPriorityQueue()
      Creates an empty PriorityQueue with the ordering given by its elements' natural ordering.
      Since:
      11.0 (but the bound of E was changed from Object to Comparable in 15.0)

    • newPriorityQueue

      public static <E extends Comparable> PriorityQueue<E> newPriorityQueue(Iterable<? extends E> elements)
      Creates a PriorityQueue containing the given elements.

      Note: If the specified iterable is a SortedSet or a PriorityQueue, this priority queue will be ordered according to the same ordering.

      Since:
      11.0 (but the bound of E was changed from Object to Comparable in 15.0)

    • newSynchronousQueue

      @GwtIncompatible public static <E> SynchronousQueue<E> newSynchronousQueue()
      Creates an empty SynchronousQueue with nonfair access policy.

    • drain

      @CanIgnoreReturnValue @GwtIncompatible public static <E> int drain(BlockingQueue<E> q, Collection<? super E> buffer, int numElements, Duration timeout) throws InterruptedException
      Drains the queue as BlockingQueue.drainTo(Collection, int), but if the requested numElements elements are not available, it will wait for them up to the specified timeout.
      Parameters:
      q - the blocking queue to be drained
      buffer - where to add the transferred elements
      numElements - the number of elements to be waited for
      timeout - how long to wait before giving up
      Returns:
      the number of elements transferred
      Throws:
      InterruptedException - if interrupted while waiting
      Since:
      28.0 (but only since 33.4.0 in the Android flavor)

    • drain

      @CanIgnoreReturnValue @GwtIncompatible public static <E> int drain(BlockingQueue<E> q, Collection<? super E> buffer, int numElements, long timeout, TimeUnit unit) throws InterruptedException
      Drains the queue as BlockingQueue.drainTo(Collection, int), but if the requested numElements elements are not available, it will wait for them up to the specified timeout.
      Parameters:
      q - the blocking queue to be drained
      buffer - where to add the transferred elements
      numElements - the number of elements to be waited for
      timeout - how long to wait before giving up, in units of unit
      unit - a TimeUnit determining how to interpret the timeout parameter
      Returns:
      the number of elements transferred
      Throws:
      InterruptedException - if interrupted while waiting

    • drainUninterruptibly

      @CanIgnoreReturnValue @GwtIncompatible public static <E> int drainUninterruptibly(BlockingQueue<E> q, Collection<? super E> buffer, int numElements, Duration timeout)
      Drains the queue as drain(BlockingQueue, Collection, int, Duration), but with a different behavior in case it is interrupted while waiting. In that case, the operation will continue as usual, and in the end the thread's interruption status will be set (no InterruptedException is thrown).
      Parameters:
      q - the blocking queue to be drained
      buffer - where to add the transferred elements
      numElements - the number of elements to be waited for
      timeout - how long to wait before giving up
      Returns:
      the number of elements transferred
      Since:
      28.0 (but only since 33.4.0 in the Android flavor)

    • drainUninterruptibly

      @CanIgnoreReturnValue @GwtIncompatible public static <E> int drainUninterruptibly(BlockingQueue<E> q, Collection<? super E> buffer, int numElements, long timeout, TimeUnit unit)
      Drains the queue as drain(BlockingQueue, Collection, int, long, TimeUnit), but with a different behavior in case it is interrupted while waiting. In that case, the operation will continue as usual, and in the end the thread's interruption status will be set (no InterruptedException is thrown).
      Parameters:
      q - the blocking queue to be drained
      buffer - where to add the transferred elements
      numElements - the number of elements to be waited for
      timeout - how long to wait before giving up, in units of unit
      unit - a TimeUnit determining how to interpret the timeout parameter
      Returns:
      the number of elements transferred

    • synchronizedQueue

      public static <E extends @Nullable Object> Queue<E> synchronizedQueue(Queue<E> queue)
      Returns a synchronized (thread-safe) queue backed by the specified queue. In order to guarantee serial access, it is critical that all access to the backing queue is accomplished through the returned queue.

      It is imperative that the user manually synchronize on the returned queue when accessing the queue's iterator: 

      
 Queue<E> queue = Queues.synchronizedQueue(MinMaxPriorityQueue.<E>create());
 ...
 queue.add(element);  // Needn't be in synchronized block
 ...
 synchronized (queue) {  // Must synchronize on queue!
   Iterator<E> i = queue.iterator(); // Must be in synchronized block
   while (i.hasNext()) {
     foo(i.next());
   }
 }

      Failure to follow this advice may result in non-deterministic behavior.

      The returned queue will be serializable if the specified queue is serializable.

      Parameters:
      queue - the queue to be wrapped in a synchronized view
      Returns:
      a synchronized view of the specified queue
      Since:
      14.0

    • synchronizedDeque

      public static <E extends @Nullable Object> Deque<E> synchronizedDeque(Deque<E> deque)
      Returns a synchronized (thread-safe) deque backed by the specified deque. In order to guarantee serial access, it is critical that all access to the backing deque is accomplished through the returned deque.

      It is imperative that the user manually synchronize on the returned deque when accessing any of the deque's iterators: 

      
 Deque<E> deque = Queues.synchronizedDeque(Queues.<E>newArrayDeque());
 ...
 deque.add(element);  // Needn't be in synchronized block
 ...
 synchronized (deque) {  // Must synchronize on deque!
   Iterator<E> i = deque.iterator(); // Must be in synchronized block
   while (i.hasNext()) {
     foo(i.next());
   }
 }

      Failure to follow this advice may result in non-deterministic behavior.

      The returned deque will be serializable if the specified deque is serializable.

      Parameters:
      deque - the deque to be wrapped in a synchronized view
      Returns:
      a synchronized view of the specified deque
      Since:
      15.0