Colt 1.0.2

edu.oswego.cs.dl.util.concurrent
Class BoundedLinkedQueue

java.lang.Object
  |
  +--edu.oswego.cs.dl.util.concurrent.BoundedLinkedQueue
All Implemented Interfaces:
BoundedChannel, Channel, Puttable, Takable

public class BoundedLinkedQueue
extends Object
implements BoundedChannel

A bounded variant of LinkedQueue class. This class may be preferable to BoundedBuffer because it allows a bit more concurency among puts and takes, because it does not pre-allocate fixed storage for elements, and allows capacity to be dynamically reset. On the other hand, since it allocates a node object on each put, it can be slow on systems with slow allocation and GC. Also, it may be preferable to LinkedQueue when you need to limit the capacity to prevent resource exhaustion. This protection normally does not hurt much performance-wise: When the queue is not empty or full, most puts and takes are still usually able to execute concurrently.

See Also:
LinkedQueue,

[ Introduction to this package. ]


Constructor Summary
BoundedLinkedQueue()
          Create a queue with the current default capacity
BoundedLinkedQueue(int capacity)
          Create a queue with the given capacity
 
Method Summary
 int capacity()
          Return the current capacity of this queue
 boolean isEmpty()
           
 boolean offer(Object x, long msecs)
          Place item in channel only if it can be accepted within msecs milliseconds.
 Object peek()
          Return, but do not remove object at head of Channel, or null if it is empty.
 Object poll(long msecs)
          Return and remove an item from channel only if one is available within msecs milliseconds.
 void put(Object x)
          Place item in the channel, possibly waiting indefinitely until it can be accepted.
 void setCapacity(int newCapacity)
          Reset the capacity of this queue.
 int size()
          Return the number of elements in the queue.
 Object take()
          Return and remove an item from channel, possibly waiting indefinitely until such an item exists.
 
Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

BoundedLinkedQueue

public BoundedLinkedQueue()
Create a queue with the current default capacity

BoundedLinkedQueue

public BoundedLinkedQueue(int capacity)
Create a queue with the given capacity
Throws:
IllegalArgumentException - if capacity less or equal to zero
Method Detail

capacity

public int capacity()
Return the current capacity of this queue
Specified by:
capacity in interface BoundedChannel
Following copied from interface: edu.oswego.cs.dl.util.concurrent.BoundedChannel
Returns:
the capacity of this channel.

isEmpty

public boolean isEmpty()

offer

public boolean offer(Object x,
                     long msecs)
              throws InterruptedException
Description copied from interface: Channel
Place item in channel only if it can be accepted within msecs milliseconds. The time bound is interpreted in a coarse-grained, best-effort fashion.
Specified by:
offer in interface Channel
Following copied from interface: edu.oswego.cs.dl.util.concurrent.Channel
Parameters:
item - the element to be inserted. Should be non-null.
msecs - the number of milliseconds to wait. If less than or equal to zero, the method does not perform any timed waits, but might still require access to a synchronization lock, which can impose unbounded delay if there is a lot of contention for the channel.
Returns:
true if accepted, else false
Throws:
InterruptedException - if the current thread has been interrupted at a point at which interruption is detected, in which case the element is guaranteed not to be inserted (i.e., is equivalent to a false return).

peek

public Object peek()
Description copied from interface: Channel
Return, but do not remove object at head of Channel, or null if it is empty.
Specified by:
peek in interface Channel

poll

public Object poll(long msecs)
            throws InterruptedException
Description copied from interface: Channel
Return and remove an item from channel only if one is available within msecs milliseconds. The time bound is interpreted in a coarse grained, best-effort fashion.
Specified by:
poll in interface Channel
Following copied from interface: edu.oswego.cs.dl.util.concurrent.Channel
Parameters:
msecs - the number of milliseconds to wait. If less than or equal to zero, the operation does not perform any timed waits, but might still require access to a synchronization lock, which can impose unbounded delay if there is a lot of contention for the channel.
Returns:
some item, or null if the channel is empty.
Throws:
InterruptedException - if the current thread has been interrupted at a point at which interruption is detected, in which case state of the channel is unchanged (i.e., equivalent to a null return).

put

public void put(Object x)
         throws InterruptedException
Description copied from interface: Channel
Place item in the channel, possibly waiting indefinitely until it can be accepted. Channels implementing the BoundedChannel subinterface are generally guaranteed to block on puts upon reaching capacity, but other implementations may or may not block.
Specified by:
put in interface Channel
Following copied from interface: edu.oswego.cs.dl.util.concurrent.Channel
Parameters:
item - the element to be inserted. Should be non-null.
Throws:
InterruptedException - if the current thread has been interrupted at a point at which interruption is detected, in which case the element is guaranteed not to be inserted. Otherwise, on normal return, the element is guaranteed to have been inserted.

setCapacity

public void setCapacity(int newCapacity)
Reset the capacity of this queue. If the new capacity is less than the old capacity, existing elements are NOT removed, but incoming puts will not proceed until the number of elements is less than the new capacity.
Throws:
IllegalArgumentException - if capacity less or equal to zero

size

public int size()
Return the number of elements in the queue. This is only a snapshot value, that may be in the midst of changing. The returned value will be unreliable in the presence of active puts and takes, and should only be used as a heuristic estimate, for example for resource monitoring purposes.

take

public Object take()
            throws InterruptedException
Description copied from interface: Channel
Return and remove an item from channel, possibly waiting indefinitely until such an item exists.
Specified by:
take in interface Channel
Following copied from interface: edu.oswego.cs.dl.util.concurrent.Channel
Returns:
some item from the channel. Different implementations may guarantee various properties (such as FIFO) about that item
Throws:
InterruptedException - if the current thread has been interrupted at a point at which interruption is detected, in which case state of the channel is unchanged.

Colt 1.0.2

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