String[] array = s.split(",");

public ArrayList<String> myList = new ArrayList<String>();
myList =s.split(",");//error:cannot convert from String[] to ArrayList<String>

array.length

public ArrayList<String> myList = new ArrayList<String>();
String[] array = s.split(",");
myList = Arrays.asList(array);

array.length

String s;
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
   s.length();
}