fix:Couple of fixes for "rare" conditions.

Author: antononcube

Java/TriesWithFrequencies/src/TrieFunctions.java

@@ -151,6 +151,9 @@ public static Trie merge(Trie tr1, Trie tr2) {
 
         } else if (!tr1.getKey().equals(tr2.getKey())) {
 
+            // This is wrong, but with this implementation is does not happen.
+            // (Or at least has not been detected.)
+            // With the tipycal trie creation with "" root, the merge in the next logical branch happens.
             res.getChildren().putAll(tr1.getChildren());
             res.getChildren().putAll(tr2.getChildren());
 
@@ -300,7 +303,6 @@ public static List<List<String>> mapPosition(Trie tr, List<List<String>> words)
     //! @description Retrieval of a sub-trie corresponding to a "word".
     //! @param tr a trie object
     //! @param word a list of strings
-    //! @param
     public static Trie retrieve(Trie tr, List<String> word) {
 
         if (word == null || word.isEmpty()) {
@@ -987,12 +989,12 @@ public static Trie map( Trie tr,  TrieNodeFunction preFunc, TrieNodeFunction pos
 
             }
 
+            res.setChildren( resChildren );
+
             if ( postFunc != null ) {
                 res = postFunc.apply(res);
             }
 
-            res.setChildren( resChildren );
-
             return res;
         }
     }