如何获得arraylist的所有组合？

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

public class ArrayListCombinations {
    public static void main(String[] args) {
        ArrayList<Integer> list = new ArrayList<>();
        list.add(1);
        list.add(2);
        list.add(3);

        List<List<Integer>> combinations = getCombinations(list);
        for (List<Integer> combination : combinations) {
            System.out.println(combination);
        }
    }

    public static List<List<Integer>> getCombinations(ArrayList<Integer> list) {
        List<List<Integer>> result = new ArrayList<>();
        if (list.isEmpty()) {
            result.add(new ArrayList<>());
            return result;
        }

        Integer first = list.remove(0);
        List<List<Integer>> subCombinations = getCombinations(list);
        result.addAll(subCombinations);

        for (List<Integer> subCombination : subCombinations) {
            List<Integer> newCombination = new ArrayList<>(subCombination);
            newCombination.add(first);
            result.add(newCombination);
        }

        return result;
    }
}

[]
[3]
[2]
[2, 3]
[1]
[1, 3]
[1, 2]
[1, 2, 3]