code: public static final String getThreadId() {
          String id = threadids.get();
          if (null == id) {
              // Pad the tid out to 8 characters
              id = getThreadId(Thread.currentThread());
              threadids.set(id);
          }
          return id;
      }
docs: Get and return the thread id, padded to 8 characters.
  
  @return 8 character string representation of thread id