Add docu

src/de/tudarmstadt/maki/simonstrator/api/common/graph/EdgeID.java

@@ -49,16 +49,24 @@ public class EdgeID extends GraphElementID {
 		return id;
 	}
 
-	private static int determineHashCode(String str) {
-		if (str.matches("\\d+->\\d+"))
-		{
-			final String[] segments = str.split("->");
+	/**
+	 * This method calculates the hash code for the given edge ID.
+	 * 
+	 * If the ID has the specific format for directed edges (e.g., 12->541),
+	 * then the hash code is calculated in a way that avoids hash collisions (at
+	 * least for node counts up to 1e5).
+	 * 
+	 * @param edgeId
+	 * @return the hash code to be used
+	 */
+	private static int determineHashCode(String edgeId) {
+		if (edgeId.matches("\\d+->\\d+")) {
+			final String[] segments = edgeId.split("->");
 			final int sourceId = Integer.parseInt(segments[0]);
 			final int targetId = Integer.parseInt(segments[1]);
 			return sourceId * 100000 + targetId;
-		}
-		else {
-			return str.hashCode();
+		} else {
+			return edgeId.hashCode();
 		}
 	}