What is the Simplest Way to Reverse an ArrayList?

Question

What is the simplest way to reverse this ArrayList?

ArrayList<Integer> aList = new ArrayList<>();  //Add elements to ArrayList object aList.add("1"); aList.add("2"); aList.add("3"); aList.add("4"); aList.add("5");  while (aList.listIterator().hasPrevious())   Log.d("reverse", "" + aList.listIterator().previous()); 

Answer 1

Collections.reverse(aList); 

Example (Reference):

ArrayList aList = new ArrayList(); //Add elements to ArrayList object aList.add("1"); aList.add("2"); aList.add("3"); aList.add("4"); aList.add("5"); Collections.reverse(aList); System.out.println("After Reverse Order, ArrayList Contains : " + aList); 

Answer 2

Not the simplest way but if you're a fan of recursion you might be interested in the following method to reverse an ArrayList:

public ArrayList<Object> reverse(ArrayList<Object> list) {     if(list.size() > 1) {                            Object value = list.remove(0);         reverse(list);         list.add(value);     }     return list; } 

Or non-recursively:

public ArrayList<Object> reverse(ArrayList<Object> list) {     for(int i = 0, j = list.size() - 1; i < j; i++) {         list.add(i, list.remove(j));     }     return list; }