A database allows for random access to records, whereas a sequential file can only be read in order. In addition, databases are schema-driven, and sequential files are processed directly.
A2:
The Java Database Connection (JDBC) made up of a dialect of SQL and set of objects that access databases in an operating system-independent fashion.
A3:
The Insert command adds rows to a table.
A4:
The access to the database is either done in the Listener methods or in private methods that are called by the Listener methods.