public int indexOf(PdfObject o){
  if (o == null)   return list.indexOf(null);
  int index=0;
  for (  PdfObject pdfObject : this) {
    if (PdfObject.equalContent(o,pdfObject)) {
      return index;
    }
    index++;
  }
  return -1;
}

public int indexOf ( PdfObject o ) { if ( o == null ) return list . indexOf ( null ) ; int index = 0 ; for ( PdfObject pdfObject : this ) { if ( PdfObject . equalContent ( o , pdfObject ) ) { return index ; } index ++ ; } return - 1 ; }
gets the first index of the specified pdfobject .
