//Now
String[] upcase(String[] input) {
  return Arrays.stream(input)
               .map(String::toUpperCase)
               .toArray(String[]::new);
}

//before
String[] upcase(String[] input) {
  String[] result = new String[input.length]

  for (int i = 0; i < input.length; i++) {
    result[i] = input[i].toUpperCase;
  }

  return result;
}