Java — Lambda expressions, Functional interfaces, Stream API

Today, you can do Java functional programming with some of the agentic coding tools.

**However, very often, a Java knowledge test in interviews involves live coding related to Java functional programming.

These questions with solutions can be a quick reminder for your interview test because you don’t do Java functional programming every day.**

Enjoy solving these questions. My recommendation:

Put some effort into solving, for example 15 minutes
If you can’t solve the problem in 15 minutes, look at the solution and try to understand it.
After understanding the solution, try to write the solution code yourself without looking at the solution.

1. Given a list of integers, separate odd and even numbers? Solution 01

2. How do you remove duplicate elements from a list using Java 8 streams? Solution 02

3. How do you remove duplicate elements from a list using Java 8 streams? Solution 03

4. How do you find frequency of each element in an array or a list? Solution 04

5. How do you sort the given list of decimals in reverse order? Solution 05

6. Given a list of strings, join the strings with ‘[‘ as prefix, ‘]’ as suffix and ‘,’ as delimiter? Solution 06

7. From the given list of integers, print the numbers which are multiples of 5? Solution 07

8. Given a list of integers, find maximum and minimum of those numbers? Solution 08

9. How do you merge two unsorted arrays into single sorted array using Java 8 streams? Solution 09

10. How do you merge two unsorted arrays into single sorted array without duplicates? Solution 10

11. How do you get three maximum numbers and three minimum numbers from the given list of integers? Solution 11

12. Java 8 program to check if two strings are anagrams or not? Solution 12

13. Find sum of all digits of a number in Java 8? Solution 13

14. Find second largest number in an integer array? Solution 14

15. Given a list of strings, sort them according to increasing order of their length? Solution 15

16. Given an integer array, find sum and average of all elements? Solution 16
    

17. How do you find common elements between two arrays? Solution 17

18. Reverse each word of a string using Java 8 streams? Solution 18

19. How do you find sum of first 10 natural numbers? Solution 19

20. Reverse an integer array Solution 20

21. Print first 10 even numbers Solution 21

22. How do you find the most repeated element in an array? Solution 22

23. Palindrome program using Java 8 streams Solution 23

24. Given a list of strings, find out those strings which start with a number? Solution 24

25. How do you extract duplicate elements from an array? Solution 25

26. Print duplicate characters in a string? Solution 26

27. Find first repeated character in a string? Solution 27

28. Find first non-repeated character in a string? Solution 28

29. Fibonacci series Solution 29

30. First 10 odd numbers Solution 30

31. How do you get last element of an array? Solution 31

32. Find the age of a person in years if the birthday has given? Solution 32

GitHub with source code: https://github.com/Milan-Karajovic/JavaFunctionalProgrammingTest

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𝐏𝐨𝐫𝐭𝐟𝐨𝐥𝐢𝐨: https://milan.karajovic.rs

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