Thread: Node.java problem

I dont understand what is wrong with this :/

Code:

 Node.java:5: error while writing Node: Node.class (Access is denied)
public class Node {
       ^
Note: client.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.
1 error
Press any key to continue . . .

It happens every time when i try to compile.