private Integer getUid(Object obj) {
      Integer uid = uids.get(obj);
      if (uid == null) {
        // One or more integer values could be skipped in the event of a race
        // to generate a UID for the same object from multiple threads, but
        // that shouldn't be a problem.
        uid = counter.getAndIncrement();
        Integer alreadySet = uids.putIfAbsent(obj, uid);
        if (alreadySet != null) {

            .buildOrThrow();
    ImmutableSet<String> uppercaseAcronyms =
        ImmutableSet.of(
            "CH", "ID", "DNT", "DNS", "DPR", "ECT", "HTTP2", "IP", "MD5", "P3P", "RTT", "TE", "UA",
            "UID", "URL", "WWW", "XSS");
    assertConstantNameMatchesString(HttpHeaders.class, specialCases, uppercaseAcronyms);
  }

  // Visible for other tests to use
  static void assertConstantNameMatchesString(
      Class<?> clazz,

            .buildOrThrow();
    ImmutableSet<String> uppercaseAcronyms =
        ImmutableSet.of(
            "CH", "ID", "DNT", "DNS", "DPR", "ECT", "GPC", "HTTP2", "IP", "MD5", "P3P", "RTT", "TE",
            "UA", "UID", "URL", "WWW", "XSS");
    assertConstantNameMatchesString(HttpHeaders.class, specialCases, uppercaseAcronyms);
  }

  // Visible for other tests to use
  static void assertConstantNameMatchesString(
      Class<?> clazz,

      }
    }
  }

  // This happens to be the hash of the class as of now. So setting it makes a backward compatible
  // change. Going forward, if any incompatible change is added, we can change the UID back to 1.
  private static final long serialVersionUID = 3637540370352322684L;