String.valueOf() Memory Leak inside of thread.

If anyone could shed some light, I'd appreciate it.

I have a simple class with a main method. Inside the main method is a
loop. Each iteration of that loop instantiates an anonymous thread
whose run method contains a single line:

String str = String.valueOf(1);

This is causing a memory leak. If I change the line to read "String
str = "String.valueOf("1"); there is no problem. Also, if I do
something like: String str = "Hello world!"; there is also no problem.

If I use String.valueOf(1); inside the loop but outside of the thread,
there is no problem. Can anyone see why garbage collection is not
occurring inside the thread?

Thanks.

--Bradley

public class Main {
     public static void main(String[] args) {
          Thread thread = null;
          for ( int intLoop = 0; intLoop < 10000; intLoop++ ) {
               String myString;
               myString = String.valueOf(1);
               thread = new Thread() {
                    public void run() {
                         String str = String.valueOf(1);
                    }
               };
               thread.start();
               thread=null;
               System.gc();
          }
     }
}