private void ensureBuilders(){
  if (this.builders == null) {
    this.builders=new ArrayList<SingleFieldBuilder<MType,BType,IType>>(messages.size());
    for (int i=0; i < messages.size(); i++) {
      builders.add(null);
    }
  }
}

private void ensureBuilders ( ) { if ( this . builders == null ) { this . builders = new ArrayList < SingleFieldBuilder < MType , BType , IType > > ( messages . size ( ) ) ; for ( int i = 0 ; i < messages . size ( ) ; i ++ ) { builders . add ( null ) ; } } }
ensures that the list of builders is not null . if it ' s null , the list is created and initialized to be the same size as the messages list with null entries .
