net.sf.javagimmicks.collections.composite.CompositeIterator Maven / Gradle / Ivy

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package net.sf.javagimmicks.collections.composite;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;

import net.sf.javagimmicks.collections.transformer.Transformer;
import net.sf.javagimmicks.collections.transformer.TransformerUtils15;

class CompositeIterator implements Iterator
{
   protected final Iterator> _iterators;
   
   protected Iterator _currentIterator;
   protected Iterator _nextIterator;
   
   CompositeIterator(List> iterators)
   {
      _iterators = iterators.iterator();
      
      findNextIterator();
   }
   
   static > CompositeIterator fromCollectionList(List collections)
   {
      final Transformer> iteratorExtractor = new Transformer>()
      {
         public Iterator transform(C source)
         {
            return source.iterator();
         }
      };
      
      final List> iteratorList = new ArrayList>(TransformerUtils15.decorate(collections, iteratorExtractor));
      
      return new CompositeIterator(iteratorList);
   }
   
   public boolean hasNext()
   {
      if(_currentIterator != null && _currentIterator.hasNext())
      {
         return true;
      }
      
      findNextIterator();
      return _nextIterator != null && _nextIterator.hasNext();
   }
   
   public E next()
   {
      if(!hasNext())
      {
         throw new NoSuchElementException();
      }
      
      return moveNext();
   }
   
   public void remove()
   {
      if(_currentIterator == null)
      {
         throw new IllegalStateException();
      }
      
      _currentIterator.remove();
   }
   
   protected void findNextIterator()
   {
      if(_nextIterator != null)
      {
         return;
      }
      
      while(_iterators.hasNext())
      {
          _nextIterator = _iterators.next();
          
          if(_nextIterator.hasNext())
          {
             break;
          }
      }
   }

   protected E moveNext()
   {
      if(_nextIterator != null)
      {
         _currentIterator = _nextIterator;
         _nextIterator = null;
      }
      
      return _currentIterator.next();
   }
}