@NonNull not throwing compile error

import org.eclipse.jdt.annotation.NonNull;

  public class NullAnnotationTest {

        public void meth1(@NonNull String in) {
            System.out.println(in.length());
        }

        public static void main(String[] args) {
            NullAnnotationTest test = new NullAnnotationTest();

            test.meth1(null);
        }
    }

If we have @NonNull annotation, i thought we will get compile time error if we call meth1 with a null argument. But i am not seeing any sort of errors or warning in the above program. Can some correct me?