How to use

sum

method

in

java.lang.Integer

int six = IntStream.of(1, 2, 3)
 .reduce(0, (a, b) -> Integer.sum(a, b));

for (char c : characters)
 map.merge(
   Character.valueOf(c),
   Integer.valueOf(1),
   (a, b) -> Integer.valueOf(Integer.sum(a.intValue(), b.intValue())));

 Map<String, Integer> frequency = new HashMap<>();

try (Scanner scanner = new Scanner(new File("path/to/file"), "UTF-8")) {
  while (scanner.hasNext()) {
    String temp = scanner.nextLine();
    if(frequency.containsKey(temp)) {
      Integer count = frequency.get(temp);
      frequency.put(temp, Integer.sum(count, 1));
    } else {
      frequency.put(temp, 1);
    }
  }
}

 LocalTime time1 = LocalTime.of(12, 30);
LocalTime time2 = LocalTime.of(8, 30);
Integer hour1 = time1.getHour();
Integer hour2 = time2.getHour();
Integer minute1 = time1.getMinute();
Integer minute2 = time2.getMinute();

Integer first = Integer.sum(hour1,hour2);
Integer second = Integer.sum(minute1,minute2);

System.out.println("The time is "+ first + " : " + second);

public static void main(String[] args) {
  Comparator<Person> byAge = (p1, p2) -> {
    return Integer.compare(p1.getAge(), p2.getAge());
  };
  Comparator<Person> byFirstName = (p1, p2) -> {
    return p1.getFirstName().compareTo(p2.getFirstName());
  };
  Comparator<Person> byAgeThenFirstName = byAge.thenComparing(byFirstName);
  Calculator sum = (a, b) -> Integer.sum(a, b);
  Calculator multiply = (a, b) -> a * b;
  Calculator divide = (a, b) -> a / b;
  System.out.println(sum.calculate(10, 20));
  System.out.println(multiply.calculate(10, 2));
  System.out.println(divide.calculate(20, 2));
}