Effective swapping of elements of an array in Java

This should make it seamless:

public static final <T> void swap (T[] a, int i, int j) {
  T t = a[i];
  a[i] = a[j];
  a[j] = t;
}

public static final <T> void swap (List<T> l, int i, int j) {
  Collections.<T>swap(l, i, j);
}

private void test() {
  String [] a = {"Hello", "Goodbye"};
  swap(a, 0, 1);
  System.out.println("a:"+Arrays.toString(a));
  List<String> l = new ArrayList<String>(Arrays.asList(a));
  swap(l, 0, 1);
  System.out.println("l:"+l);
}

Nope. You could have a function to make it more concise each place you use it, but in the end, the work done would be the same (plus the overhead of the function call, until/unless HotSpot moved it inline — to help it with that, make the functon static final).

If you're swapping numbers and want a concise way to write the code without creating a separate function or using a confusing XOR hack, I find this is much easier to understand and it's also a one liner.

public static void swap(int[] arr, int i, int j) {
    arr[i] = (arr[i] + arr[j]) - (arr[j] = arr[i]);
}

What I've seen from some primitive benchmarks is that the performance difference is basically negligible as well.

This is one of the standard ways for swapping array elements without using a temporary variable, at least for integers.