versions4Java9To11Features

1package pkg2versions;2 3/*4 * versions4Java9To11Features.java5 * ----------------------6 * Cumulative Java 9-11 example. The whole file requires Java 11.7 * It is not a Java 9 or Java 10 program: var is Java 10, and the8 * String methods below are Java 11. Collection uses Collectors.toList(),9 * which is Java 8. It does not call the Java 16 Stream toList method.10 *11 * FEATURES & WHY:12 *  Java 9  : Module system (JPMS), collection factory methods (List.of),13 *            private interface methods, Stream.takeWhile/dropWhile.14 *  Java 10 : `var` local variable type inference.15 *  Java 11 : new String methods (strip, isBlank, lines, repeat),16 *            Files.readString/writeString, the standard HttpClient, run .java directly.17 *  (Java 11 is an LTS release.)18 */19import java.util.*;20import java.util.stream.*;21 22public class versions4Java9To11Features {23    public static void main(String[] args) {24        // Java 9: immutable collection factories25        List<Integer> list = List.of(1, 2, 3);26        Map<String, Integer> map = Map.of("a", 1, "b", 2);27        Set<String> set = Set.of("x", "y");28        System.out.println("factories: " + list + " " + map + " " + set);29 30        // Java 9: takeWhile / dropWhile31        List<Integer> taken = Stream.of(1, 2, 3, 4, 1).takeWhile(x -> x < 4).collect(Collectors.toList());32        List<Integer> dropped = Stream.of(1, 2, 3, 4, 1).dropWhile(x -> x < 4).collect(Collectors.toList());33        System.out.println("takeWhile<4: " + taken + " dropWhile<4: " + dropped);34 35        // Java 10: var36        var greeting = "hello";37        var numbers = new ArrayList<Integer>();38        numbers.add(42);39        System.out.println("var: " + greeting + " " + numbers);40 41        // Java 11: String methods42        System.out.println("isBlank: " + "   ".isBlank());43        System.out.println("strip: [" + "  hi  ".strip() + "]");44        System.out.println("repeat: " + "=".repeat(10));45        "line1\nline2\nline3".lines().forEach(l -> System.out.println("  " + l));46    }47}