TwoSum

public static int[] findTwoSum(int[] list, int sum) {
    Map<Integer, Integer> integerMap = new HashMap<>();
    System.out.println("sum: " + sum);
    if (list == null || list.length < 2)
        return null;
    for (int i = 0; i < list.length; i++) {
        int ch = sum - list[i];
        if( integerMap.containsKey(ch)){
            return new int[]{i, integerMap.get(ch)};
        } else {
            integerMap.put(list[i], i);
        }
    }
    return null;
}