How do I reverse an int array in Java?

Question

I am trying to reverse an int array in Java.

This method does not reverse the array.

for(int i = 0; i < validData.length; i++)
{
    int temp =          


        

Answer 1

This is how I would personally solve it. The reason behind creating the parametrized method is to allow any array to be sorted... not just your integers.

I hope you glean something from it.

@Test
public void reverseTest(){
   Integer[] ints = { 1, 2, 3, 4 };
   Integer[] reversedInts = reverse(ints);

   assert ints[0].equals(reversedInts[3]);
   assert ints[1].equals(reversedInts[2]);
   assert ints[2].equals(reversedInts[1]);
   assert ints[3].equals(reversedInts[0]);

   reverseInPlace(reversedInts);
   assert ints[0].equals(reversedInts[0]);
}

@SuppressWarnings("unchecked")
private static  T[] reverse(T[] array) {
    if (array == null) {
        return (T[]) new ArrayList().toArray();
    }
    List copyOfArray = Arrays.asList(Arrays.copyOf(array, array.length));
    Collections.reverse(copyOfArray);
    return copyOfArray.toArray(array);
}

private static  T[] reverseInPlace(T[] array) {
    if(array == null) {
        // didn't want two unchecked suppressions
        return reverse(array);
    }

    Collections.reverse(Arrays.asList(array));
    return array;
}