Nicola Garofalo

I've just seen another mistake

you write

catch{ }

Remember that you should catch an exception in a way like:

catch(Exception e){ //... }

current e scanner are duplicate variables.

Public is not public


Remove this first issues and go on.

i have put SQL Driver.tar in classpath.

What is the exact name of the driver you put in your classpath?

Let me know if it works.

Anyway that's mysql tutorial link on connecting to mySql using DriverManager

http://dev.mysql.com/doc/refman/5.6/en/connector-j-usagenotes-connect-drivermanager.html

the problem should be here

jdbc:mysql://localhost:3306/

let's say you created a schema named mydb, the connection string must be

jdbc:mysql://localhost:3306/mydb

Probably you can't, within the same Statement, execute select queries and batch updates.

I tried it and it works...

you are welcome

Line 23 was a while and now it's an if. Put the while back

while(st.hasMoreTokens())

Could you please post the code as it is now?

No, you won't

Did you make all the changes i told you ?

You did not make all the changes i asked you to make.

1) Remove from line 14 to line 16
2) In line 18 you must read the String returned by method KbdInput.readString()

StringTokenizer st= new StringTokenizer(KbdInput.readString());

3) Remove line 19, or you will miss some tokens

Last thing.

Remove lines

BufferedReader br; br = new BufferedReader(new InputStreamReader(System.in)); String line = br.readLine();

in your main method of class Grades, because method readString() does it too, and you would end up to read two lines

KbdInput.readInt() method could lead you to a runtime exception
It reads a line and it assumes this line will be an integer.

You could delete it and remove all the instructions

input = KbdInput.readInt();

A nice method in KbdInput is readString() that returns a String that you can tokenize

Assuming that a user will enter values 60 70 40 30 -99 (but you should check user input token by token)

method readString() will return the String "60 70 40 30 -99"

You can tokenize that String with StringTokenizer

StringTokenizer st= new StringTokenizer(KbdInput.readString());

int variable input could become, for example

input = Integer.parseInt(st.nextToken());

the inner loop

while(input != -99) { //... }

it's useless and you should remove it.

Start to make this changes and see what's happening

First of all.
We should know what KbdInput class does, in particular one of its methods, readInt().
it does not return an int as expected but an empty String

Second:

You create a StringTokenizer of the String taken as input, i.e. String line

But you don't go through its tokens!!!
So the loop

while (st.hasMoreTokens()) { ... }
will probably never end

Can you post KbdInput.readInt() method?