versions3Java8Features

1package pkg2versions;2 3/*4 * versions3Java8Features.java  (2014)  -- the most important modern release5 * ----------------------------------------------------------------6 * FEATURES & WHY:7 *  - Lambdas            : functions as values; concise behavior.8 *  - Streams API        : declarative bulk data processing.9 *  - Optional           : explicit absence; avoid NullPointerException.10 *  - Default methods     : evolve interfaces without breaking implementers.11 *  - Method references  : shorthand for lambdas.12 *  - java.time          : modern, immutable date/time API.13 */14import java.util.*;15import java.util.stream.*;16import java.time.*;17 18public class versions3Java8Features {19 20    interface Named {21        String name();22        default String shout() { return name().toUpperCase(); }  // default method23    }24 25    public static void main(String[] args) {26        // Lambda implementing a functional interface27        Named n = () -> "java8";28        System.out.println("default method: " + n.shout());29 30        // Streams31        List<Integer> evens = IntStream.rangeClosed(1, 10)32                .filter(x -> x % 2 == 0)33                .boxed()34                .collect(Collectors.toList());35        System.out.println("evens 1..10: " + evens);36 37        // Method reference + collector38        String joined = Stream.of("a", "b", "c").map(String::toUpperCase).collect(Collectors.joining("-"));39        System.out.println("joined: " + joined);40 41        // Optional42        Optional<String> first = evens.stream().filter(x -> x > 100).map(String::valueOf).findFirst();43        System.out.println("optional: " + first.orElse("none"));44 45        // java.time46        LocalDate today = LocalDate.of(2024, 1, 15);47        System.out.println("plus 2 weeks: " + today.plusWeeks(2) + " | day: " + today.getDayOfWeek());48        Duration d = Duration.ofHours(2).plusMinutes(30);49        System.out.println("duration minutes: " + d.toMinutes());50    }51}