doc update

Author: mtumilowicz

README.md

@@ -65,7 +65,7 @@ and enters it into this map unless null.
     **returns** the current (existing or computed) value associated with 
     the specified key, or null if the computed value is null
 
-    **Remark**: putIfAbsent(1, null) will NOT add an entry (supposing 1 is absent)
+    **Remark**: `putIfAbsent(1, null)` will NOT add an entry (supposing 1 is absent)
 
 * `putIfAbsent` vs `computeIfAbsent`: [stackoverflow differences](https://stackoverflow.com/a/48184207)
     * different returns,
@@ -81,6 +81,8 @@ Replaces each entry's value with the result of invoking the given
 function on that entry until all entries have been processed or the
 function throws an exception
 
+    **Remark**: Can't change the element type. To do that - use a stream.
+
 * `default boolean replace(K key, V oldValue, V newValue)` - Replaces the 
 entry for the specified key only if currently mapped to the specified value.
 * `default V replace(K key, V value)` - Replaces the entry for the