public static synchronized void unregister(Class c, int classId) {
    if (c == null) {
      throw new NullPointerException(
          "Cannot unregister a null class");
    }
    final Integer idx = classId;
    final Instantiator i = (Instantiator) idsToInstantiators.remove(idx);
    if (i == null) {
      throw new IllegalArgumentException(
          String.format("Class %s was not registered with id %s", c.getName(), classId));
    } else {
      dsMap.remove(c.getName(), i);
    }
    idsToHolders.remove(idx);
    classNamesToHolders.remove(i.getInstantiatedClass().getName());
  }
Unregisters the given class with the given class id with the {@code Instantiator}.

@throws IllegalArgumentException If {@code c} was not previously registered with id
        {@code classId}.
@throws NullPointerException If {@code c} is {@code null}
geode-core/src/main/java/org/apache/geode/internal/InternalInstantiator.java