Failed to start database error

That is probably because you use "create=true" in the connection string -
you should not use it if you already created database
Table should be created with SQL command like
stmt.executeUpdate("create table....")
and you should not have create=true in connection string if you alreday have file "newdemo" with the database

I removed "create=true" from my connection code...but still the error is coming..
attaching the modified connection code... Pls help..
connection-code.txt

so error did not change at all?

Do you have newdemo folder in
C:\Users\Dell\Documents\NetBeansProjects\RCSSystem\  ?

check if you ahve file db.lck inside newdemo folder

http://db.apache.org/derby/docs/dev/devguide/cdevdvlp20458.html


Derby prevents two instances of itself from booting the same database by using a file called db.lck inside the database directory.

If a second instance of Derby attempts to boot an already running database, the following error messages appear:

ERROR XJ040: Failed to start database 'firstdb', see the next exception
for details.
ERROR XSDB6: Another instance of Derby may have already booted the
database /home/myself/DERBYTUTOR/firstdb.

In addition, a stack trace appears in the derby.log file. For help diagnosing a double boot problem, use the derby.stream.error.logBootTrace property to obtain information about both successful and unsuccessful boot attempts. The property is described in the Derby Reference Manual.

Make sure you completely stop your application while you're working on it - iow don't have another instance running in another thread