Home Tasks Solved Problems for the Lambda, Functional Interfaces, Stream API Module

Running the tests

Find the TestNG Test Runner XML file located in src/test/java/resources Right-click -> Run

Additionaly, you can run the following command in the terminal

mvn test

Home Tasks Requirements:

Don’t use: if-else, char, switch-case Use: stream, java 8+

IMPORTANT:

1. Implement Unit Tests for each task.

• Task 1:

1. Show in console Stream stream = Stream.of(1,2,3,4,5,6,7,8,9);
2. Create a list of random numbers using Stream.generate() , should have 20 items and print in console
3. Collect Stream elements to a List: Convert list elements to stream, select only even ones, use the collect method to collect them into a List:

• Task 2:

List list = new ArrayList(); for(int i = 1, i < 10; i++){ list.add(i) }

4. Repeat the same as in task 3 but collect all the elements in Array [];
5. filter values, keep those that start with "c", convert all values, convert to uppercase, sort in Descending order List myList = Arrays.asList("a1", "a2", "b1", "c2", "c1");

• Task 3:

6. a) Display names that start with ‘A’ and have length > 5; b) Sort all names and display them in lower case on the screen List memberNames = new ArrayList<>(); memberNames.add("Amitabh"); memberNames.add("Shekhar"); memberNames.add("Aman"); memberNames.add("Rahul"); memberNames.add("Shahrukh"); memberNames.add("Abibaba"); memberNames.add("Salman"); memberNames.add("Yana"); memberNames.add("Lokesh");

7. Stream.match() - Various matching operations can be used to check whether a given predicate matches the stream elements. Match returns a boolean result. From task 6, take an array and check with allMatch or anyMatch whether the list contains names with the letter ‘S’ (allMatch should display false, anyMatch should display true) From task 6, take an array and check with noneMatch whether the list contains names with the letter ‘H’ (should display true)

8. Stream.count() - The count() is a terminal operation returning the number of elements in the stream as a long value.

9. From task 6 count the number of names starting with “A” - display their number.

10. Stream.findFirst() - take the array from task 6 and print the first name starting with ‘L’

• Task 4:

11. Java Stream flatMap() - concatenate 3 arrays into one using flatMap () List list1 = Arrays.asList(1,2,3); List list2 = Arrays.asList(4,5,6); List list3 = Arrays.asList(7,8,9);

12. And these are also combined into 1 String[][] dataArray = new String[][]{{"a", "b"}, {"c", "d"}, {"e", "f"}, {"g", "h"}}; Stream.distinct() to remove duplicates - remove duplicates from this array and display.

13. ArrayList numbersList = new ArrayList<>(Arrays.asList(1, 1, 2, 3, 3, 3, 4, 5, 6, 6, 6, 7)); (OPTIONAL, NOT MANDATORY) Collectors.toMap() - move the list into Map where the key is an element of the array and the value is the number of times the element occurs in the array ArrayList numbersList = new ArrayList<>(Arrays.asList(1, 1, 2, 3, 3, 3, 4, 5, 6, 6, 6, 7));

14. Write to a new list only letters that occur in the values of this map Map<String, List> people = new HashMap<>(); people.put("John", Arrays.asList("555-1123","s", "555-3389", "a")); people.put("Mary", Arrays.asList("555-2243","z", "555-5264")); people.put("Steve", Arrays.asList("555-6654", "555-3242", "d"));