Package com.google.common.collect

Class Queues

  • 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

    • Method Detail

      • newArrayBlockingQueue

        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

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

      • newConcurrentLinkedQueue

        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

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

      • newLinkedBlockingDeque

        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

        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

        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

        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

        public static <E extends Comparable> PriorityBlockingQueue<E> newPriorityBlockingQueue()
        Creates an empty PriorityBlockingQueue with the ordering given by its elements' natural ordering.
        Since:
        11.0 (requires that E be Comparable since 15.0).

      • newPriorityBlockingQueue

        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 (requires that E be Comparable since 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 (requires that E be Comparable since 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 (requires that E be Comparable since 15.0).

      • newSynchronousQueue

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

      • drain

        @Beta
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

        @Beta
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

        @Beta
public static <E> 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

        @Beta
public static <E> 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