public static int getClassId(Class c) {
    int result = 0;
    final Instantiator i = dsMap.get(c.getName());
    if (i != null) {
      result = i.getId();
    } else {
      InstantiatorAttributesHolder iah = classNamesToHolders.get(c.getName());
      if (iah != null) {
        result = iah.getId();
      }
    }
    return result;
  }
Returns the class id for the given class.

@return {@code 0} if the class has not be registered

@see DataSerializer#writeObject(Object, DataOutput)
geode-core/src/main/java/org/apache/geode/internal/InternalInstantiator.java