Rotating an array by a certain amount (2 ways)

rotate.py

def rotate (array, amount):
  return array[amount:] + array[:amount]

Rotator.java

package io.github.davepkennedy;

import java.util.ArrayList;
import java.util.List;

/**
 * Created by dakennedy on 29/11/2016.
 */
public class Rotator {
    public static List<Integer> simpleRotate (List<Integer> numbers, int amount) {
        List<Integer> intermediate = new ArrayList<>();
        while (intermediate.size() < numbers.size()) {
            intermediate.add(numbers.get(amount));
            amount += 1;
            if (amount >= numbers.size()) {
                amount = 0;
            }
        }
        return intermediate;
    }

    public static List <Integer> complexRotate (final List<Integer> numbers, int amount) {
        List <Integer> result = new ArrayList<>(numbers);
        List <Integer> subList = result.subList(0, amount);
        result.addAll(subList);
        return result.subList(amount, result.size());
    }
}

This is way too simple

• To rotate 2m numbers, I need 2 arrays of 2m numbers. Memory use is 2*n
• Rotating to a copy is O(n)
• Rotating in place would require 2*n copies -> O(2n)

Doing it in python looks cool

• What's happening under the hood? It could be akin to the Java approach when it comes to join the slices
• How efficient is it with lots of data?