code: @Deprecated
      public static void register(final Tracer tracer) {
          if (!registerIfAbsent(provide(tracer))
                  && !tracer.equals(GlobalTracer.tracer)
                  && !(tracer instanceof GlobalTracer)) {
              throw new IllegalStateException("There is already a current global Tracer registered.");
          }
      }
docs: Register a {@link Tracer} to back the behaviour of the {@link #get() global tracer}.
  <p>
  Registration is a one-time operation, attempting to call it more often will result in a runtime exception.
  <p>
  Every application intending to use the global tracer is responsible for registering it once
  during its initialization.
  
  @param tracer Tracer to use as global tracer.
  @throws RuntimeException if there is already a current tracer registered
  @see #registerIfAbsent(Callable)
  @deprecated Please use {@link #registerIfAbsent(Tracer)} or {@link #registerIfAbsent(Callable)} instead.