public static void main(String[] args) {

//[[0, 2], [1, 5], [0, 9], [2, 15]];

Integer[][] keyTimes = new Integer[][]{{0, 2}, {1, 5}, {0, 9}, {2, 15}};

List<List<Integer>> listKeyTimes = new LinkedList<>();

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

Integer[] keyTime = keyTimes[i];

List<Integer> ints = Arrays.asList(keyTime);

listKeyTimes.add(ints);

}

char ch = slowestKey(listKeyTimes);

System.out.printf("Slowest key: %s\n", ch);

}

public static char slowestKey(List<List<Integer>> keyTimes) {

int longestPress = 0;

int longestPressKey = 0;

for (int i = 0; i < keyTimes.size() - 1; i++) {

int key = keyTimes.get(i).get(0);

int countPressed = keyTimes.get(i).get(1);

if (i == 0) {

longestPressKey = key;

longestPress = countPressed;

}

int key2 = keyTimes.get(i + 1).get(0);

int countPressed2 = keyTimes.get(i + 1).get(1);

int diff = countPressed2 - countPressed;

if (longestPress < diff) {

longestPress = diff;

longestPressKey = key2;

}

}

char ch = keyToChar(longestPressKey);

return ch;

}

private static char keyToChar(int key) {

return (char) ((char) key + 'a');

}

}