diff --git a/OsmAnd-java/src/net/osmand/util/Algorithms.java b/OsmAnd-java/src/net/osmand/util/Algorithms.java
index c6303810ae..8f1bae7cbf 100644
--- a/OsmAnd-java/src/net/osmand/util/Algorithms.java
+++ b/OsmAnd-java/src/net/osmand/util/Algorithms.java
@@ -20,11 +20,12 @@ import java.util.Collection;
 import java.util.Collections;
 import java.util.Comparator;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.Iterator;
-import java.util.List;
 import java.util.Locale;
 import java.util.Map;
 import java.util.Map.Entry;
+import java.util.Set;
 
 
 /**
@@ -177,22 +178,18 @@ public class Algorithms {
 		return "";
 	}
 
-	public static List<String> decodeCollection(String s) {
+	public static Set<String> decodeStringSet(String s) {
 		if (isEmpty(s)) {
-			return Collections.emptyList();
+			return Collections.emptySet();
 		}
-		return Arrays.asList(s.split(CHAR_TOSPLIT + ""));
+		return new HashSet<>(Arrays.asList(s.split(CHAR_TOSPLIT + "")));
 	}
 
-	public static String encodeCollection(Collection<String> collection) {
-		if (collection != null) {
-			Iterator<String> it = collection.iterator();
+	public static String encodeStringSet(Set<String> set) {
+		if (set != null) {
 			StringBuilder sb = new StringBuilder();
-			while (it.hasNext()) {
-				sb.append(it.next());
-				if (it.hasNext()) {
-					sb.append(CHAR_TOSPLIT);
-				}
+			for (String s : set) {
+				sb.append(s).append(CHAR_TOSPLIT);
 			}
 			return sb.toString();
 		}
diff --git a/OsmAnd/src/net/osmand/plus/GPXDatabase.java b/OsmAnd/src/net/osmand/plus/GPXDatabase.java
index 4d9ca952c6..983d09fba6 100644
--- a/OsmAnd/src/net/osmand/plus/GPXDatabase.java
+++ b/OsmAnd/src/net/osmand/plus/GPXDatabase.java
@@ -12,7 +12,6 @@ import net.osmand.util.Algorithms;
 
 import java.io.File;
 import java.util.ArrayList;
-import java.util.HashSet;
 import java.util.List;
 
 public class GPXDatabase {
@@ -273,7 +272,7 @@ public class GPXDatabase {
 							db.execSQL("UPDATE " + GPX_TABLE_NAME + " SET " +
 											GPX_COL_WPT_CATEGORY_NAMES + " = ? " +
 											" WHERE " + GPX_COL_NAME + " = ? AND " + GPX_COL_DIR + " = ?",
-									new Object[] { Algorithms.encodeCollection(gpxFile.getWaypointCategories(true)), fileName, fileDir });
+									new Object[] { Algorithms.encodeStringSet(gpxFile.getWaypointCategories(true)), fileName, fileDir });
 						}
 					} finally {
 						db.close();
@@ -425,7 +424,7 @@ public class GPXDatabase {
 							a.timeSpan, a.timeMoving, a.totalDistanceMoving, a.diffElevationUp, a.diffElevationDown,
 							a.avgElevation, a.minElevation, a.maxElevation, a.maxSpeed, a.avgSpeed, a.points, a.wptPoints,
 							color, item.file.lastModified(), item.splitType, item.splitInterval, item.apiImported ? 1 : 0,
-							Algorithms.encodeCollection(item.analysis.wptCategoryNames)});
+							Algorithms.encodeStringSet(item.analysis.wptCategoryNames)});
 		} else {
 			db.execSQL("INSERT INTO " + GPX_TABLE_NAME + "(" +
 							GPX_COL_NAME + ", " +
@@ -470,7 +469,7 @@ public class GPXDatabase {
 								a.timeSpan, a.timeMoving, a.totalDistanceMoving, a.diffElevationUp,
 								a.diffElevationDown, a.avgElevation, a.minElevation, a.maxElevation,
 								a.maxSpeed, a.avgSpeed, a.points, a.wptPoints, item.file.lastModified(),
-								Algorithms.encodeCollection(a.wptCategoryNames), fileName, fileDir });
+								Algorithms.encodeStringSet(a.wptCategoryNames), fileName, fileDir });
 			} finally {
 				db.close();
 			}
@@ -523,7 +522,7 @@ public class GPXDatabase {
 		a.avgSpeed = avgSpeed;
 		a.points = points;
 		a.wptPoints = wptPoints;
-		a.wptCategoryNames = new HashSet<>(Algorithms.decodeCollection(wptCategoryNames));
+		a.wptCategoryNames = Algorithms.decodeStringSet(wptCategoryNames);
 
 		File dir;
 		if (!Algorithms.isEmpty(fileDir)) {