Java 8 Programs

Java 8 Programs

Program to ADD PREFIX and SUFFIX to the STRING?
- StringJoiner class, used to add prefix and suffix in a given String
     StringJoiner stringJoiner = new StringJoiner(",", "#", "#");
     stringJoiner.add("Interview");
     stringJoiner.add("Questions");
     stringJoiner.add("Answers");
     System.out.println(stringJoiner);

Program to PRINT 10 RANDOM NUMBERs using forEach?

- Use Random class to generate Random number

     Random random = new Random();

     random.ints().limit(10).forEach(System.out::println);

Program to iterate a Stream using the forEach method?

     List<String> str = Arrays.asList("Hello","Hola","Namaste","Hi");

     str.stream().forEach(System.out::println);

Program to find the Minimum and Maximum number of a Stream?

To find minimum or maximum number in stream, use comparator.comparing() method which will take integer value from Stream.

     Integer min = Stream.of(1, 2, 3, 4, 5, 6,7).min(Comparator.comparing(Integer::valueOf)).get();

     Integer max = Stream.of(1, 2, 3, 4, 5, 6,7).max(Comparator.comparing(Integer::valueOf)).get();

Program to Print Strings whose length is greater than 3 in List?

     List<String> stringList = Arrays.asList("Hello","Interview","Questions","Answers","Ram","for");

     stringList.stream().filter(str -> str.length() > 3).forEach(System.out::println);

Program to multiply 3 to all element in list and print the list?

use map() function, will perform operation and will generate new stream with updated value

     List<Integer> integerList = Arrays.asList(1,2,3,4,5,6,7);

     System.out.println(integerList.stream().map(i -> i*3).collect(Collectors.toList()));

Program to perform concatenation on two Streams?

     List<Integer> integerList1 = Arrays.asList(1,2,3,4);

     List<Integer> integerList2 = Arrays.asList(5,6,7);

     Stream<Integer> concatStream = Stream.concat(integerList1.stream(), integerList2.stream());

     concatStream.forEach(System.out::print);

Program to REMOVE the DUPLICATE elements from the list?

To remove duplicate element form list, use Collectors.toSet()

     List<Integer> integerList = Arrays.asList(1,2,3,4,1,2,3);

     integerList.stream().collect(Collectors.toSet()).forEach(System.out::print);

Print current date and time, in Date and Time API?

To get current date and time we are using LocalDate, LocalTime, and LocalDateTime API provided

     System.out.println("Current Date: " + java.time.LocalDate.now());

     System.out.println("Current Time: " + java.time.LocalTime.now());

     System.out.println("Current Date and Time: " + java.time.LocalDateTime.now());

Program to SORT the given list?

To Sort the integer element given in List, use sorted() method which will sort the List elements.

     List<Integer> integerList = Arrays.asList(4,5,6,7,1,2,3);

     integerList.stream().sorted().forEach(System.out::println); //AO

     integerList.stream().sorted(Comparator.reverseOrder()).forEach(System.out::println); //DO

To find FIND 2 BIGGEST elements:

     integerList.stream().sorted(Comparator.reverseOrder()).limit(2).forEach(System.out::println);

To find statistics, max, min, count, sum,

     integerList.stream().mapToInt((x)->x).summaryStatistics();

Program to get the SUM of all numbers present in a list?

     List<Integer> integerList = Arrays.asList(4,5,6,7,1,2,3);

     System.out.println(integerList.stream().mapToInt(Integer::intValue).sum());

Program to perfrom cube on list elements and filter numbers greater than 50.

     List<Integer> integerList = Arrays.asList(4,5,6,7,1,2,3);

     integerList.stream().map(i -> i*i*i).filter(i -> i>50).forEach(System.out::println);

Stream.reduce()

In Java 8, the Stream.reduce() combine elements of a stream and produces a single value.

     int[] numbers = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

     int sum = Arrays.stream(numbers).reduce(0, Integer::sum);

     int sum = Arrays.stream(numbers).reduce(0, (a, b) -> a + b);

     int max1 = Arrays.stream(numbers).reduce(0, Integer::max);

     int min1 = Arrays.stream(numbers).reduce(0, Integer::min);

Program to convert list to MAP?

int[] array = new int[] { 18, 67, 134, 87, 11, 11 };

List<Integer> list = Arrays.stream(array).boxed().collect(Collectors.toList());

Map<Integer, Long> map = list.stream().collect(Collectors.groupingBy(Function.identity(), Collectors.counting()));

List<String> names = Arrays.asList("John", "Mary", "Bob");

Map<String, Integer> nameMap = names.stream().collect(Collectors.toMap(name -> name, name -> name.length()));

Program to apply groupingBy and Comparator in Employee List?

// find highest salary employee in each department

Map<String, Optional<Employee>> highestPaidByDept =  empList.stream().collect(Collectors.groupingBy(Employee::getDepartment, Collectors.maxBy(Comparator.comparingDouble(Employee::getSalary))));

// list of employees whose salary is less than 10000 and sort in descending order on name

empList.stream().filter(e -> e.getSalary() < 10000).sorted(Comparator.comparing(Employee::getName).reversed()).forEach(System.out::println);