Java 8 Stream Api Interview questions

1. Find maximum and minimum from array using stream api.

List <Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);

int max = numbers.stream().max(Integer::compare).get();
int min = numbers.stream().min(Integer::compare).get();

2. find the even and odd number sum from given array.

int evenSum = numbers.stream().filter(num->num%2==0)
                              .mapToInteger(Integer::intValue)
                              .sum();

int oddSum = numbers.stream().filter(num->num%2!=0)
                             .mapToInteger(Integer::intValue)
                             .sum();

3. find the unique number from given array

List <Integer> numbers = Arrays.asList(1, 2, 2, 3, 3, 3, 4, 4, 4, 5, 6, 7, 8, 9, 10); 

List<Integer> uniqueNumbers = numbers.stream().distinct().collect(Collectors.toList()); 

4. Find the second largest number from the given array list.

int second   =   numbers.stream()
                 .sorted(Comparator.comparing(Integer::intValue)
                 .reversed())
                 .skip(1)
                 .findFirst()
                 .get();

System.out.println("second largest number " + second);

5. add plus one to every element of the array

List<Integer> list = numbers.stream().map(num -> num + 1).collect(Collectors.toList());