Question

What is the difference between String and String... and what is the difference between Void and Void... in this context?

class AddStringsTask extends AsyncTask<Void, String, Void>{

        @Override
        protected Void doInBackground(Void... unused) {
            for (String item: items){
                publishProgress(item);
                SystemClock.sleep(200);
            }
            return(null);
        }

        @Override
        protected void onProgressUpdate(String... item){
            ((ArrayAdapter)getListAdapter()).add(item[0]);
        }

        @Override
        protected void onPostExecute(Void unused){
            Toast.makeText(Cap15Asyncer.this,"Completed!" , Toast.LENGTH_SHORT).show();
        }   
    }   

Answer 1

In the method

protected void onProgressUpdate(String... item){
    ((ArrayAdapter)getListAdapter()).add(item[0]);
}

String... item Means that the method takes an arbitrary number of Strings (including 0 Strings). So this method can be called with any number of strings as input, and it will add them all to the listAdapter, like an array. If the method was:

protected void onProgressUpdate(String item){
    ((ArrayAdapter)getListAdapter()).add(item);
}

Then it would take exactly one String, (note the add method has changed accordingly).