VPackInstanceCreators preserve collections entries order

Author: rashtao

ChangeLog.md

@@ -6,6 +6,8 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/) a
 
 ## [Unreleased]
 
+- Map and Set VPackInstanceCreators preserve collections entries order (based on `LinkedHashSet` and `LinkedHashMap`) 
+
 ## [2.1.0] - 2019-12-20
 
 - added [tags support](https://github.com/arangodb/velocypack/blob/master/VelocyPack.md#tagging)

src/main/java/com/arangodb/velocypack/internal/VPackInstanceCreators.java

@@ -20,16 +20,10 @@
 
 package com.arangodb.velocypack.internal;
 
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.HashMap;
-import java.util.HashSet;
-import java.util.List;
-import java.util.Map;
-import java.util.Set;
-
 import com.arangodb.velocypack.VPackInstanceCreator;
 
+import java.util.*;
+
 /**
  * @author Mark Vollmary
  *
@@ -56,13 +50,13 @@ public List createInstance() {
 	public static final VPackInstanceCreator<Set> SET = new VPackInstanceCreator<Set>() {
 		@Override
 		public Set createInstance() {
-			return new HashSet();
+			return new LinkedHashSet();
 		}
 	};
 	public static final VPackInstanceCreator<Map> MAP = new VPackInstanceCreator<Map>() {
 		@Override
 		public Map createInstance() {
-			return new HashMap();
+			return new LinkedHashMap();
 		}
 	};