java.io.filepermission access denied error

the code has a part in which it has to write (append) in a file
i have created that file,the code it saves the entered data in the file.

But when i open it, its not there
this particular exception is thrown

Quote:

java.security.accesscontrolexception access denied (java.io.filepermission

i have also changed policy file, but to no avail
i have tried signing the application, but i think it went wrong somewhere

can anyone tell me the "exact" syntax of command that i have to enter in java.policy file?