implement a first simple point location algorithm

VadereUtils/src/org/vadere/util/delaunay/Face.java

@@ -2,7 +2,6 @@ package org.vadere.util.delaunay;
 
 import org.jetbrains.annotations.NotNull;
 import org.vadere.util.geometry.shapes.VPoint;
-
 import org.vadere.util.geometry.shapes.VPolygon;
 
 import java.awt.geom.Path2D;
@@ -12,7 +11,6 @@ import java.util.List;
 import java.util.stream.Stream;
 import java.util.stream.StreamSupport;
 
-
 public class Face implements Iterable<HalfEdge> {
 
 	/**
@@ -62,13 +60,11 @@ public class Face implements Iterable<HalfEdge> {
 		return new VPolygon(path2D);
 	}
 
-
 	@Override
 	public Iterator<HalfEdge> iterator() {
 		return new HalfEdgeIterator();
 	}
 
-
 	public Stream<HalfEdge> stream () {
 		Iterable<HalfEdge> iterable = () -> iterator();
 		return StreamSupport.stream(iterable.spliterator(), false);

VadereUtils/src/org/vadere/util/delaunay/HalfEdge.java

@@ -4,7 +4,7 @@ import org.jetbrains.annotations.NotNull;
 
 import org.vadere.util.geometry.shapes.VLine;
 import org.vadere.util.geometry.shapes.VPoint;
-
+import java.util.Optional;
 
 /**
  * Created by bzoennchen on 13.11.16.
@@ -38,9 +38,7 @@ public class HalfEdge {
 	private Face face;
 
 
-
-
-	public HalfEdge (final VPoint end, final Face face) {
+	public HalfEdge (@NotNull final VPoint end, @NotNull final Face face) {
 		this.end = end;
 		this.face = face;
 	}
@@ -66,14 +64,14 @@ public class HalfEdge {
 	}
 
 
-	public HalfEdge getTwin() {
-		return twin;
+	public Optional<HalfEdge> getTwin() {
+		return Optional.ofNullable(twin);
 	}
 
 	public void setTwin(final @NotNull HalfEdge twin) {
 		this.twin = twin;
 
-		if(twin.getTwin() != this) {
+		if(!twin.getTwin().isPresent() || twin.getTwin().get() != this) {
 			twin.setTwin(this);
 		}
 	}