title: Why this code how read a shapefile using geotools throws this exception?
body: <p>I'm reading attributes from a shapefile using geotools 10.1.
  I don't understand why throws an exception after print all features attribute.</p>
  
  <p>This is the example code:</p>
  
  <pre><code>import java.io.File;
  import java.io.IOException;
  import java.io.Serializable;
  import java.util.HashMap;
  import java.util.Map;
  
  import org.geotools.data.DataStore;
  import org.geotools.data.DataStoreFinder;
  import org.geotools.data.FeatureSource;
  import org.geotools.feature.FeatureCollection;
  import org.geotools.feature.FeatureIterator;
  import org.opengis.feature.simple.SimpleFeature;
  
  public class LayerBusinessTest {
  
  
  public static void main(String[] args) throws IOException {
  
      File file = new File("../../setup/test/shp/sscc/SSCC2010_WGS84.shp");
      Map&lt;String, Serializable&gt; map = new HashMap&lt;&gt;();
      map.put( "url", file.toURI().toURL() );
  
      DataStore dataStore = DataStoreFinder.getDataStore( map );
      String typeName = dataStore.getTypeNames()[0];
  
      FeatureSource source = dataStore.getFeatureSource( typeName );
  
      FeatureCollection collection =  source.getFeatures();
      FeatureIterator&lt;SimpleFeature&gt; results = collection.features();
      try {
          while (results.hasNext()) {
              SimpleFeature feature = (SimpleFeature) results.next();
              String code = feature.getAttribute("Codigo_SSC").toString();
              System.out.println( code );
          }
      } finally {
          results.close();
      }
  
  }
  </code></pre>
  
  <p>}</p>
  
  <p>Exception:</p>
  
  <pre><code>Exception in thread "main" java.lang.IllegalArgumentException: Expected requestor org.geotools.data.shapefile.dbf.DbaseFileReader@2ac9b619 to have locked the url but it does not hold the lock for the URL
      at org.geotools.data.shapefile.files.ShpFiles.unlockRead(ShpFiles.java:429)
      at org.geotools.data.shapefile.files.FileChannelDecorator.implCloseChannel(FileChannelDecorator.java:149)
      at java.nio.channels.spi.AbstractInterruptibleChannel.close(AbstractInterruptibleChannel.java:115)
      at org.geotools.data.shapefile.dbf.DbaseFileReader.close(DbaseFileReader.java:279)
      at org.geotools.data.shapefile.ShapefileFeatureReader.close(ShapefileFeatureReader.java:248)
      at org.geotools.data.store.ContentFeatureCollection$WrappingFeatureIterator.close(ContentFeatureCollection.java:154)
      at LayerBusinessTest.main(LayerBusinessTest.java:39)
  </code></pre>