public static <T> T checkNotNull(
      T reference, String errorMessageTemplate, Object... errorMessageArgs) {
    if (reference == null) {
      // If either of these parameters is null, the right thing happens anyway
      throw new NullPointerException(format(errorMessageTemplate, errorMessageArgs));
    }
    return reference;
  }
Copy of {@code com.google.common.base.Preconditions#checkNotNull}.
core/src/main/java/feign/Util.java