notifi listen tree drastic chang structur given node path return path length element doe identifi current root node element root tree em note em swing method invok swing awt event thread param sourc object respons gener event typic creator event object pass valu param path arrai object identifi path parent modifi item element arrai object store root node element object store parent node param child indic arrai specifi index valu remov item indic sort order lowest highest param children arrai object contain insert remov chang object tree model listen tree structur chang tree model event tree structur chang object sourc object path child indic object children guarante non arrai object listen listen list listen list tree model event process listen notifi interest event listen length listen tree model listen lazili creat event tree model event sourc path child indic children tree model listen listen tree structur chang 