public String next(int n) {
            int current = mark();
            int start = mark();
            for (int i = 0; i != n; ++i) {
                if (!hasNext()) {
                    rewindTo(start);
                    return null;
                }
                next();
            }
            return original.substring(current, position());
        }
Merge two schemas to a common schema which can represent values from both input schemas.
@param previous One Schema, non-null
@param newSchema Another schema, non-null
@return A schema that is a superset of both input schemas, or null if no common schema is found.
connect/api/src/main/java/org/apache/kafka/connect/data/Values.java