unbiasedqueue.html

jxta的api库

<DD><DL>

<DT><B>Returns:</B><DD>boolean indicating whether this queue has been closed.</DL>
</DD>
</DL>
<HR>

<A NAME="close()"><!-- --></A><H3>
close</H3>
<PRE>
public void <B>close</B>()</PRE>
<DL>
<DD>Close the queue. This will prevent any further objects from being enqueued.
<P>
<DD><DL>
</DL>
</DD>
</DL>
<HR>

<A NAME="clear()"><!-- --></A><H3>
clear</H3>
<PRE>
public void <B>clear</B>()</PRE>
<DL>
<DD>Flush the queue of all pending objects.
<P>
<DD><DL>
</DL>
</DD>
</DL>
<HR>

<A NAME="push(java.lang.Object)"><!-- --></A><H3>
push</H3>
<PRE>
public boolean <B>push</B>(java.lang.Object&nbsp;obj)</PRE>
<DL>
<DD>Attempt to push an object onto the queue. If the queue is full then the
  object will not be pushed. This method does not use any synchronization
  and should not be used if other threads are using <A HREF="../../../../net/jxta/impl/util/UnbiasedQueue.html#pop(long)"><CODE>pop(long)</CODE></A> to
  retrieve elements.
<P>
<DD><DL>
<DT><B>Parameters:</B><DD><CODE>obj</CODE> - object to push
<DT><B>Returns:</B><DD>true if the obj was pushed, otherwise false.</DL>
</DD>
</DL>
<HR>

<A NAME="pushBack(java.lang.Object)"><!-- --></A><H3>
pushBack</H3>
<PRE>
public boolean <B>pushBack</B>(java.lang.Object&nbsp;obj)</PRE>
<DL>
<DD>Attempt to push an object back at the head the queue. If the queue is
  full then the object will not be pushed. This method does not use any
 synchronization and should not be used if other threads are using
 <A HREF="../../../../net/jxta/impl/util/UnbiasedQueue.html#pop(long)"><CODE>pop(long)</CODE></A> to retrieve elements.
<P>
<DD><DL>
<DT><B>Parameters:</B><DD><CODE>obj</CODE> - object to push
<DT><B>Returns:</B><DD>true if the obj was pushed, otherwise false.</DL>
</DD>
</DL>
<HR>

<A NAME="push(java.lang.Object, long)"><!-- --></A><H3>
push</H3>
<PRE>
public boolean <B>push</B>(java.lang.Object&nbsp;obj,
                    long&nbsp;timeout)
             throws java.lang.InterruptedException</PRE>
<DL>
<DD>Push an object onto the queue. If the queue is full then the push will
  wait for up to "timeout" milliseconds to push the object. At the end of
  "timeout" milliseconds, the push will either return false or remove the
  oldest item from the queue and insert "obj". This behaviour is contolled
  by the constructor parameter "dropOldest".
<P>
<DD><DL>
<DT><B>Parameters:</B><DD><CODE>obj</CODE> - Object to be pushed onto the queue<DD><CODE>timeout</CODE> - Time in milliseconds to try to insert the item into a full
  queue. Per Java standards, a timeout of "0" (zero) will wait indefinitly.
  Negative values force no wait period at all.
<DT><B>Returns:</B><DD>true if the object was intersted into the queue, otherwise false.
<DT><B>Throws:</B>
<DD><CODE>java.lang.InterruptedException</CODE> - if the operation is interrupted before
      the timeout interval is completed.</DL>
</DD>
</DL>
<HR>

<A NAME="pushBack(java.lang.Object, long)"><!-- --></A><H3>
pushBack</H3>
<PRE>
public boolean <B>pushBack</B>(java.lang.Object&nbsp;obj,
                        long&nbsp;timeout)
                 throws java.lang.InterruptedException</PRE>
<DL>
<DD>Push an object back at the head of the queue. If the queue is full then
  the push will wait for up to "timeout" milliseconds to push the object.
  At the end of "timeout" milliseconds, the push will either return false
  or remove the oldest item from the queue and insert "obj". This behaviour
  is contolled by the constructor parameter "dropOldest".

  <p/>Timeout control is accomplished via synchronization and
  <CODE>Object.wait(long)</CODE>. <A HREF="../../../../net/jxta/impl/util/UnbiasedQueue.html#pushBack(java.lang.Object, long)"><CODE>pushBack(Object,long)</CODE></A> should only
  be used in conjunction with <A HREF="../../../../net/jxta/impl/util/UnbiasedQueue.html#push(java.lang.Object, long)"><CODE>push(Object,long)</CODE></A> and
  <A HREF="../../../../net/jxta/impl/util/UnbiasedQueue.html#pop(long)"><CODE>pop(long)</CODE></A>
<P>
<DD><DL>
<DT><B>Parameters:</B><DD><CODE>obj</CODE> - Object to be pushed onto the queue<DD><CODE>timeout</CODE> - Time in milliseconds to try to insert the item into a full
  queue. Per Java standards, a timeout of "0" (zero) will wait indefinitly.
  Negative values force no wait period at all.
<DT><B>Returns:</B><DD><tt>true</tt> if the object was intersted into the queue,
  otherwise <tt>false</tt>.
<DT><B>Throws:</B>
<DD><CODE>java.lang.InterruptedException</CODE> - if the operation is interrupted before
  the timeout interval is completed.</DL>
</DD>
</DL>
<HR>

<A NAME="peek()"><!-- --></A><H3>
peek</H3>
<PRE>
public java.lang.Object <B>peek</B>()</PRE>
<DL>
<DD>Return the next Object from the queue without removing it.
<P>
<DD><DL>

<DT><B>Returns:</B><DD>Object, null if the queue is empty.</DL>
</DD>
</DL>
<HR>

<A NAME="pop()"><!-- --></A><H3>
pop</H3>
<PRE>
public java.lang.Object <B>pop</B>()</PRE>
<DL>
<DD>Remove and return the next Object from the queue.
<P>
<DD><DL>

<DT><B>Returns:</B><DD>Object, null if the queue is empty.</DL>
</DD>
</DL>
<HR>

<A NAME="pop(long)"><!-- --></A><H3>
pop</H3>
<PRE>
public java.lang.Object <B>pop</B>(long&nbsp;timeout)
                     throws java.lang.InterruptedException</PRE>
<DL>
<DD>Gets a Object from the queue. If no Object is immediately available,
 then wait the specified amount of time for an Object to be inserted.
<P>
<DD><DL>
<DT><B>Parameters:</B><DD><CODE>timeout</CODE> - Amount of time to wait in milliseconds for an object to
 be available. Per Java convention, a timeout of zero (0) means wait an
 infinite amount of time. Negative values mean do not wait at all.
<DT><B>Returns:</B><DD>The next object in the queue.
<DT><B>Throws:</B>
<DD><CODE>java.lang.InterruptedException</CODE> - if the operation is interrupted before
 the timeout interval is completed.</DL>
</DD>
</DL>
<HR>

<A NAME="popMulti(int)"><!-- --></A><H3>
popMulti</H3>
<PRE>
public java.lang.Object[] <B>popMulti</B>(int&nbsp;maxObjs)</PRE>
<DL>
<DD>Returns an array of objects, possibly empty, from the queue.
<P>
<DD><DL>
<DT><B>Parameters:</B><DD><CODE>maxObjs</CODE> - the maximum number of items to return.
<DT><B>Returns:</B><DD>an array of objects, possibly empty containing the returned
  queue elements.</DL>
</DD>
</DL>
<HR>

<A NAME="getMaxQueueSize()"><!-- --></A><H3>
getMaxQueueSize</H3>
<PRE>
public int <B>getMaxQueueSize</B>()</PRE>
<DL>
<DD>How many objects will fit in this queue
<P>
<DD><DL>

<DT><B>Returns:</B><DD>int indicating how many objects will fit in the queue.</DL>
</DD>
</DL>
<HR>

<A NAME="setMaxQueueSize(int)"><!-- --></A><H3>
setMaxQueueSize</H3>
<PRE>
public void <B>setMaxQueueSize</B>(int&nbsp;maxObjs)</PRE>
<DL>
<DD>Set how many objects this queue may store. Note that if there are more
  objects already in the queue than the specified amount then the queue
  will retain its current capacity.
<P>
<DD><DL>
<DT><B>Parameters:</B><DD><CODE>maxObjs</CODE> - The number of objects which the queue must be able to
  store.</DL>
</DD>
</DL>
<HR>

<A NAME="getCurrentInQueue()"><!-- --></A><H3>
getCurrentInQueue</H3>
<PRE>
public int <B>getCurrentInQueue</B>()</PRE>
<DL>
<DD>Return the number of elements currently in the queue. This method is
  useful for statistical sampling, but should not be used to determine
  program logic due to the multi-threaded behaviour of these queues.

  <p/>You should use the return values and timeout behaviour of the
  <A HREF="../../../../net/jxta/impl/util/UnbiasedQueue.html#push(java.lang.Object)"><CODE>push(Object)</CODE></A> and <A HREF="../../../../net/jxta/impl/util/UnbiasedQueue.html#pop(long)"><CODE>pop(long)</CODE></A> methods to regulate how you
  use the queue.
<P>
<DD><DL>

<DT><B>Returns:</B><DD>the number of elements currently in the queue. Be warned that
  even two sequential calls to this method may return different answers
  due to activity on other threads.</DL>
</DD>
</DL>
<HR>

<A NAME="getNumEnqueued()"><!-- --></A><H3>
getNumEnqueued</H3>
<PRE>
public long <B>getNumEnqueued</B>()</PRE>
<DL>
<DD>Return the total number of objects which have been enqueued on to this
  queue during its existance.
<P>
<DD><DL>

<DT><B>Returns:</B><DD>how many objects have been queued.</DL>
</DD>
</DL>
<HR>

<A NAME="getAvgInQueueAtEnqueue()"><!-- --></A><H3>
getAvgInQueueAtEnqueue</H3>
<PRE>
public double <B>getAvgInQueueAtEnqueue</B>()</PRE>
<DL>
<DD>Return the average number of elements in the queue at Enqueue time.
<P>
<DD><DL>

<DT><B>Returns:</B><DD>average number of elements which were in the queue at during all
  of the "push" operations which returned a "true" result. Does not
  include the item being pushed. If no elements have ever been enqueued
  then "NaN" will be returned.</DL>
</DD>
</DL>
<HR>

<A NAME="getNumDequeued()"><!-- --></A><H3>
getNumDequeued</H3>
<PRE>
public long <B>getNumDequeued</B>()</PRE>
<DL>
<DD>Return the total number of objects which have been dequeued from this
  queue during its existance.
<P>
<DD><DL>

<DT><B>Returns:</B><DD>how many objects have been queued.</DL>
</DD>
</DL>
<HR>

<A NAME="getAvgInQueueAtDequeue()"><!-- --></A><H3>
getAvgInQueueAtDequeue</H3>
<PRE>
public double <B>getAvgInQueueAtDequeue</B>()</PRE>
<DL>
<DD>Return the average number of elements in the queue at dequeue time.
<P>
<DD><DL>

<DT><B>Returns:</B><DD>average number of elements which were in the queue at during all
  of the "pop" operations which returned a non-null result. Includes the
 item being "pop"ed in the average. If no elements have ever been dequeued
  then "NaN" will be returned.</DL>
</DD>
</DL>
<HR>

<A NAME="getNumDropped()"><!-- --></A><H3>
getNumDropped</H3>
<PRE>
public long <B>getNumDropped</B>()</PRE>
<DL>
<DD>Return the total number of objects which have been dropped by this queue
  during its existance.
<P>
<DD><DL>

<DT><B>Returns:</B><DD>how many objects have been dropped.</DL>
</DD>
</DL>
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