Add javadoc to Parser.addJoin()

h2/src/main/org/h2/command/Parser.java

@@ -1805,6 +1805,16 @@ public class Parser {
         return top;
     }
 
+    /**
+     * Add one join to another. This method creates nested join between them if
+     * required.
+     *
+     * @param top parent join
+     * @param join child join
+     * @param outer if child join is an outer join
+     * @param on the join condition
+     * @see TableFilter#addJoin(TableFilter, boolean, Expression)
+     */
     private void addJoin(TableFilter top, TableFilter join, boolean outer, Expression on) {
         if (join.getJoin() != null) {
             String joinTable = Constants.PREFIX_JOIN + parseIndex;