public SpanManager insert(int offset,String str){
  sb.insert(offset,str);
  adjustLists(offset,str.length());
  if (calculateSrcPositions)   for (int i=0; i < str.length(); i++)   ib.add(offset,-1);
  return this;
}

public SpanManager insert ( int offset , String str ) { sb . insert ( offset , str ) ; adjustLists ( offset , str . length ( ) ) ; if ( calculateSrcPositions ) for ( int i = 0 ; i < str . length ( ) ; i ++ ) ib . add ( offset , - 1 ) ; return this ; }
insterts a string at the position offset .
