org.limewire.collection
Class QueueCounter

java.lang.Object
  org.limewire.collection.QueueCounter

public class QueueCounter
extends java.lang.Object

Measures the average number of elements in a queueing system.

See Little's Law for more information.

 try{
         QueueCounter qc = new QueueCounter(10);
         System.out.println("Average size: " + qc.getAverageSize());
         for(int i = 0; i < 10; i++){
             qc.recordArrival();
             Thread.sleep( 1000 );
         }
         for(int i = 0; i < 10; i++)
             qc.recordDeparture();
         System.out.println("Average size: " + qc.getAverageSize());
     } catch(Exception e) {
         e.printStackTrace();
     }               
 
     Output:
         Average size: -1.0
         Average size: 5.500395106845166
 

Constructor Summary

QueueCounter(int historySize)

Method Summary

double	getAverageSize()
boolean	isStale()
void	recordArrival() Record an arrival in the system.
void	recordDeparture() Record a departure from the system.
void	reset() Forgets all recorded data.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

QueueCounter

public QueueCounter(int historySize)

Method Detail

recordArrival

public void recordArrival()

Record an arrival in the system.

recordDeparture

public void recordDeparture()

Record a departure from the system.

getAverageSize

public double getAverageSize()

Returns:

the average number of elements in the system.

isStale

public boolean isStale()

Returns:

if the system could be considered stale. More specifically, this returns true if all of the following are true:

  1. we have enough historical data and
  2. the system has been empty for longer than the period over which the 
  historical data was recorded.
 

Note that this is an arbitrary recommendation and may be completely irrelevant for some purposes.

reset

public void reset()

Forgets all recorded data.