java - populating a spinner with unique strings -

im trying populate action bar spinner unique strings based on user input in dialog box, eg user enters string , if it's not in spinner, should add there. such implementation possible ? tried using arraylist class of course, duplicates there, should use hashset ? thanks

// array of sample strings popluate dropdown list arraylist<string> categories = new arraylist<string>();  // create array adapter popluate dropdown list     arrayadapter<string> adapter = new arrayadapter<string>(             getbasecontext(),             android.r.layout.simple_spinner_dropdown_item, categories);   //thats alert dialog through user enters strings  alertdialog.builder alert = new alertdialog.builder(this);          alert.settitle("new category");         alert.setmessage("please enter new category ");          // set edittext view user input         final edittext input = new edittext(this);         alert.setview(input);          alert.setpositivebutton("ok",                 new dialoginterface.onclicklistener() {                     public void onclick(dialoginterface dialog,                             int whichbutton) {                         editable value = input.gettext();                         // value!                          categories.add(value.tostring());                      }                 }); 

i'd suggest before adding categories check if it's been added before or not using arraylist.contains: http://docs.oracle.com/javase/7/docs/api/java/util/arraylist.html#contains(java.lang.object)

another thing think case sensitivity, perhaps convert lower case before checking if exists in arraylist , adding if doesn't.