java - unceraintity with arrayList storing -

public void openfile(){         try {             l = new formatter("try.txt");             system.out.println("opened file");         } catch (exception e){             system.out.println("did not open file");         }     }     public void addrecord(){         l.format("%s", namefield.gettext());         system.out.println("added name" + " " + namefield.gettext());         }     public void onclose(){         l.close();     }  /*  trying store user data, have gui , anytime click sign want store namefield in array list, possible anytime close , reopen program , else puts in name adds array list instead of overriding earlier person put in? example in gui type in mike name, close , reopen , put in john name, add mike , john or john? , how make them co-exist? thank 

it reads file, everytime close program , run again replaces whatever on first line.

with list (of arraylist 1 implementation) can use add method. example if had list contains single object string "mike", , execute nameslist.add("john") (where nameslist list<string>) list contain 2 elements: "john" , "mike".

however, mention persisting data between program executions. default lists purely in memory data storage, , cleared each time close , reopen program. store them need form of data persistence. on heavy end full database, small project simple requirements can use sqlite - or text file.