how to update certain parts of text file in java -

i want able update line on text file. error cannot delete file, why error?

public class main {     public static void main(string[] args) {         main rlf = new main();         rlf.removelinefromfile("f:\\text.txt", "bbb");     }      public void removelinefromfile(string file, string linetoremove) {         try {             file infile = new file(file);              if (!infile.isfile()) {                 system.out.println("parameter not existing file");                 return;             }              //construct new file later renamed original filename.             file tempfile = new file(infile.getabsolutepath() + ".tmp");              bufferedreader br = new bufferedreader(new filereader(file));             printwriter pw = new printwriter(new filewriter(tempfile));              string line = null;              //read original file , write new             //unless content matches data removed.             while ((line = br.readline()) != null) {                  if (!line.trim().equals(linetoremove)) {                      pw.println(line);                     pw.flush();                 }             }             pw.close();             br.close();              //delete original file             if (!infile.delete()) {                 system.out.println("could not delete file");                 return;             }              //rename new file filename original file had.             if (!tempfile.renameto(infile)) system.out.println("could not rename file");          }         catch (filenotfoundexception ex) {             ex.printstacktrace();         }         catch (ioexception ex) {             ex.printstacktrace();         }     } }​ 

the program works me. perhaps having environmental issue.