net.sf.javagimmicks.collections8.composite.CompositeEnumeration Maven / Gradle / Ivy

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Utility classes, APIs and tools for Java

There is a newer version: 0.99-alpha1

package net.sf.javagimmicks.collections8.composite;

import java.util.Enumeration;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;

class CompositeEnumeration implements Enumeration
{
   protected final Iterator> _enumerations;

   protected Enumeration _currentEnumeration;
   protected Enumeration _nextEnumeration;

   CompositeEnumeration(final List> enumerations)
   {
      _enumerations = enumerations.iterator();

      findNextEnumeration();
   }

   @Override
   public boolean hasMoreElements()
   {
      if (_currentEnumeration != null && _currentEnumeration.hasMoreElements())
      {
         return true;
      }

      findNextEnumeration();
      return _nextEnumeration != null && _nextEnumeration.hasMoreElements();
   }

   @Override
   public E nextElement()
   {
      if (!hasMoreElements())
      {
         throw new NoSuchElementException();
      }

      return moveNext();
   }

   protected void findNextEnumeration()
   {
      if (_nextEnumeration != null)
      {
         return;
      }

      while (_enumerations.hasNext())
      {
         _nextEnumeration = _enumerations.next();

         if (_nextEnumeration.hasMoreElements())
         {
            break;
         }
      }
   }

   protected E moveNext()
   {
      if (_nextEnumeration != null)
      {
         _currentEnumeration = _nextEnumeration;
         _nextEnumeration = null;
      }

      return _currentEnumeration.nextElement();
   }
}