if (obj == null) throw new NullPointerException();
  private void put32(Object obj, int value) {    if (isStatic()) {      VM_Statics.setSlotContents( offset >>> LOG_BYTES_IN_INT, value );    } else {      if (obj == null) throw new NullPointerException();      VM_Magic.setIntAtOffset(obj, offset, value);    }  }