code: public void addInterface(String interfaceName) {
          short interfaceIndex = itsConstantPool.addClass(interfaceName);
          itsInterfaces.add(Short.valueOf(interfaceIndex));
      }
docs: Add an interface implemented by this class.
  
  This method may be called multiple times for classes that implement multiple interfaces.
  
  @param interfaceName a name of an interface implemented by the class being written, including
  full package qualification.