package org.exolab.castor.mapping.loader.collection.handler;
   
   import java.util.Enumeration;
   import java.util.PriorityQueue;
   import java.util.Queue;
   
   import org.exolab.castor.mapping.CollectionHandler;
   import org.exolab.castor.mapping.loader.CollectionHandlers;
   import org.exolab.castor.mapping.loader.J2CollectionHandlers.IteratorEnumerator;
  
  public final class QueueCollectionHandler<T> implements CollectionHandler<T> {
  
     @SuppressWarnings("unchecked")
     public Object add(Object collection, T object) {
        if (collection == null) {
           collection = new PriorityQueue<T>();
           ((Queue<T>) collection).add(object);
           return collection;
        }
        ((Queue<T>) collection).add(object);
        return null;
     }
  
     @SuppressWarnings("unchecked")
     public Enumeration<T> elements(Object collection) {
        if (collection == null)
           return new CollectionHandlers.EmptyEnumerator<T>();
        return new IteratorEnumerator<T>(((Queue<T>) collection).iterator());
     }
  
     @SuppressWarnings("unchecked")
     public int size(Object collection) {
        if (collection == null)
           return 0;
        return ((Queue<T>) collection).size();
     }
  
     @SuppressWarnings("unchecked")
     public Object clear(Object collection) {
        if (collection != null)
           ((Queue<T>) collection).clear();
        return null;
     }
  
     public String toString() {
        return "Queue";
     }
  }