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instance variable in helper class is thread safe ?

mike zhang
Ranch Hand

Joined: Feb 26, 2002
Posts: 59
I know the instance variables in a servlet are NOT thread safe, in the following code:
public class MyServlet extends HttpServlet {
public void doGet(HttpServletRequest req, HttpServletResponse res) throws ... {
Helper_1 help_1 = new Helper_1();
import javax.servlet.*;
public class Helper_1 {
private Helper_2 help_2;
public void doIt(HttpServletRequest req, HttpServletResponse res) {
help_2 = new Helper_2();
public class Helper_2 {
.... // a non-servlet class here
I defined "help_2" as a class instance varibale.
My thought is: Since "help_1" is thread safe, and "help_2" is a private instance variable of "help_1" so I don't need to worry about the thread safe issue for "help_2", is that right ?
Christopher Dixon

Joined: Jan 30, 2002
Posts: 22
You've got it. Since every call to doGet(req, resp) is a seperate thread, and the variable help_1 is declared as a local variable in the method doGet(req, resp), each thread has it's own help_1 and instance of Helper_1.
help_2 is fine (used as in your example) since no threads will be sharing an instance of Helper_1, they each have their own.
[ March 04, 2002: Message edited by: Christopher Dixon ]
I agree. Here's the link:
subject: instance variable in helper class is thread safe ?
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