Trying to define building iterator.

src/eu/simstadt/lowlevelgmlparser/CityGmlIterator.java

+package eu.simstadt.lowlevelgmlparser;
+
+import java.io.IOException;
+import java.nio.file.Path;
+import java.util.Iterator;
+import java.util.logging.Logger;
+import com.ximpleware.AutoPilot;
+import com.ximpleware.NavException;
+import com.ximpleware.VTDGen;
+import com.ximpleware.VTDNav;
+import com.ximpleware.XPathEvalException;
+import com.ximpleware.XPathParseException;
+
+
+public class CityGmlIterator implements Iterable<String>
+{
+
+	private static final Logger LOGGER = Logger.getLogger(CityGmlIterator.class.getName());
+
+	private AutoPilot buildingsFinder;
+	private VTDNav navigator;
+	private long offsetAndLength;
+	private int buildingsCount = 0;
+	private int buildingOffset = 0;
+	private int buildingLength = 0;
+
+	public CityGmlIterator(Path citygmlPath)
+			throws XPathParseException, NavException, NumberFormatException, XPathEvalException, IOException {
+		VTDGen parser = new VTDGen();
+		parser.parseFile(citygmlPath.toString(), false);
+		this.navigator = parser.getNav();
+		this.buildingsFinder = new AutoPilot(navigator);
+		buildingsFinder.selectXPath("//cityObjectMember");
+	}
+
+	@Override
+	public Iterator<String> iterator() {
+		Iterator<String> it = new Iterator<String>() {
+
+			@Override
+			public boolean hasNext() {
+				try {
+					return buildingsFinder.evalXPath() != -1;
+				} catch (XPathEvalException | NavException ex) {}
+				return false;
+			}
+
+			@Override
+			public String next() {
+				try {
+					buildingsCount += 1;
+					if (buildingsCount % 1000 == 0) {
+						LOGGER.info("1000 buildings parsed");
+					}
+					offsetAndLength = navigator.getElementFragment();
+					buildingOffset = (int) offsetAndLength;
+					buildingLength = (int) (offsetAndLength >> 32);
+					return navigator.toRawString(buildingOffset, buildingLength);
+				} catch (NavException ex) {}
+				return null;
+			}
+
+			@Override
+			public void remove() {
+				throw new UnsupportedOperationException();
+			}
+		};
+		return it;
+	}
+
+}