pig/src/main/java/com/twitter/elephantbird/pig/util/AbstractWritableConverter.java
@Override
  @SuppressWarnings("unchecked")
  public Class<W> getWritableClass() throws IOException {
    if (writable == null) {
      return null;
    }
    return (Class<W>) writable.getClass();
  }
@Override
  @SuppressWarnings("unchecked")
  public Class<W> getWritableClass() throws IOException {
    if (writable == null) {
      return null;
    }
    return (Class<W>) writable.getClass();
  }
Default implementation returns value of {@link #writableClass}.

@see com.twitter.elephantbird.pig.util.WritableConverter#getWritableClass()