StringBuffer or StringBuilder in Servlet's doFilter method? [duplicate]

Question

I'm implementing my custom filter:

public class MyFilter implements javax.servlet.Filter

Which should I use in this doFilter method - StringBuffer or StringBuilder?

I would like to use it in this way:

StringBuffer stringBuffer = new StringBuffer();
stringBuffer.append(MY_CODE_HERE);
response.sendRedirect(stringBuffer.toString());

or...

StringBuilder stringBuilder = new StringBuilder();
stringBuilder.append(MY_CODE_HERE);
response.sendRedirect(stringBuilder.toString());

I know that StringBuffer is thread safe, but would a StringBuilder be enough?

Answer 1

Local variables are thread-safe and variables declared inside the doFilter() method will be thread safe. Use StringBuilder for your purpose, as you shouldn't unnecessarily incur the overhead of synchronization used in StringBuffer.

Moreover , The Servlet request and response objects are created afresh for every new request and response and so by their nature they are thread safe. The doFilter() method will be executed in separate threads for each request.

Suggested Reading:

1. Why are local variables thread safe in Java.
2. StringBuilder and StringBuffer in Java
3. servlet-filters tag wiki