issues that were discovered during biohackathon 2019 in Paris

pathvisio/src/main/java/lcsb/mapviewer/wikipathway/model/Edge.java

 package lcsb.mapviewer.wikipathway.model;
 
-import java.awt.*;
+import java.awt.Color;
 import java.awt.geom.Point2D;
 import java.io.Serializable;
 import java.util.*;
-import java.util.List;
 
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
@@ -365,15 +364,26 @@ public class Edge implements Serializable {
    */
   public void extend(Edge edge2) {
     // check if extension make sense (they should point to the same identifier)
-    if (!getEnd().equals(edge2.getStart())) {
+    if (!Objects.equals(getEnd(), edge2.getStart())) {
       throw new InvalidArgumentException(" Cannot merge - anchor points doesn't match: " + getEnd()
           + "," + edge2.getStart());
     }
 
-    if (line.getEndPoint().distance(edge2.getLine().getBeginPoint()) > EPSILON) {
+    int mergePoint = line.getPoints().size() - 1;
+
+    while (mergePoint >= 0) {
+      if (line.getPoints().get(mergePoint).distance(edge2.getLine().getBeginPoint()) < EPSILON) {
+        break;
+      }
+      mergePoint--;
+    }
+    if (mergePoint < 0) {
       throw new InvalidArgumentException(" Cannot merge - edges are far from each other: "
-          + line.getEndPoint() + ","
-          + edge2.getLine().getBeginPoint());
+          + line + ","
+          + edge2.getLine());
+    }
+    while (mergePoint < line.getPoints().size() - 1) {
+      line.getPoints().remove(line.getPoints().size() - 1);
     }
 
     // graphId should be the same