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Jetty example source code file (ArrayQueue.java)
This example Jetty source code file (ArrayQueue.java) is included in the DevDaily.com
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Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.
The Jetty ArrayQueue.java source code
package org.mortbay.util;
import java.util.AbstractList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;
import java.util.Queue;
/* ------------------------------------------------------------ */
/** Queue backed by circular array.
*
* This partial Queue implementation (also with {@link #pop()} for stack operation)
* is backed by a growable circular array.
*
* @author gregw
*
* @param <E>
*/
public class ArrayQueue<E> extends AbstractList implements Queue
{
private Object[] _elements;
private int _nextE;
private int _nextSlot;
private int _size;
private int _growCapacity;
public ArrayQueue()
{
_elements=new Object[64];
_growCapacity=32;
}
public ArrayQueue(int capacity)
{
_elements=new Object[capacity];
_growCapacity=-1;
}
public ArrayQueue(int initCapacity,int growBy)
{
_elements=new Object[initCapacity];
_growCapacity=growBy;
}
public synchronized boolean add(E e)
{
_size++;
_elements[_nextSlot++]=e;
if (_nextSlot==_elements.length)
_nextSlot=0;
if (_nextSlot==_nextE)
{
if (_growCapacity<=0)
throw new IllegalStateException("Full");
Object[] elements=new Object[_elements.length+_growCapacity];
int split=_elements.length-_nextE;
if (split>0)
System.arraycopy(_elements,_nextE,elements,0,split);
if (_nextE!=0)
System.arraycopy(_elements,0,elements,split,_nextSlot);
_elements=elements;
_nextE=0;
_nextSlot=_size;
}
return true;
}
public synchronized E element()
{
if (_nextSlot==_nextE)
throw new NoSuchElementException();
return (E)_elements[_nextE];
}
public synchronized boolean offer(E e)
{
_size++;
_elements[_nextSlot++]=e;
if (_nextSlot==_elements.length)
_nextSlot=0;
if (_nextSlot==_nextE)
{
if (_growCapacity<=0)
return false;
Object[] elements=new Object[_elements.length+_growCapacity];
int split=_elements.length-_nextE;
if (split>0)
System.arraycopy(_elements,_nextE,elements,0,split);
if (_nextE!=0)
System.arraycopy(_elements,0,elements,split,_nextSlot);
_elements=elements;
_nextE=0;
_nextSlot=_size;
}
return true;
}
public synchronized E peek()
{
if (_nextSlot==_nextE)
return null;
return (E)_elements[_nextE];
}
public synchronized E poll()
{
if (_size==0)
return null;
E e = (E)_elements[_nextE];
_elements[_nextE]=null;
_size--;
if (++_nextE==_elements.length)
_nextE=0;
return e;
}
public synchronized E remove()
{
if (_nextSlot==_nextE)
throw new NoSuchElementException();
E e = (E)_elements[_nextE++];
if (_nextE==_elements.length)
_nextE=0;
return e;
}
public synchronized void clear()
{
_size=0;
_nextE=0;
_nextSlot=0;
}
/* ------------------------------------------------------------ */
public boolean isEmpty()
{
return _size==0;
}
/* ------------------------------------------------------------ */
public int size()
{
return _size;
}
/* ------------------------------------------------------------ */
public synchronized E get(int index)
{
if (index>=_size)
throw new IndexOutOfBoundsException(index+">="+_size);
int i = _nextE+index;
if (i>=_elements.length)
i-=_elements.length;
return (E)_elements[i];
}
}
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