java8新特性学习笔记

使用lambda表达式排序

  Collections.sort(temp, (String a, String b) -> {
            return b.compareTo(a);
        });
    
        Collections.sort(temp, (String a, String b) -> b.compareTo(a));

Stream使用

  List<String> test = Arrays.asList("a", "a1", "a2", "b", "b1", "b2", "c", "c1", "ab");

        // 过滤
        test.stream().filter(s -> s.contains("a")).forEach(System.out::println);

        // 排序
        test.stream().sorted().forEach(System.out::println);
        // 映射
        test.stream().map(String::toUpperCase).forEach(System.out::println);
        // 匹配
        boolean a = test.stream().allMatch(s -> s.contains("a"));
        boolean b = test.stream().anyMatch(s -> s.contains("a"));
        boolean c = test.stream().noneMatch(s -> s.contains("a"));
        System.out.println(a + "," + b + "," + c);

        // 计数
        long res = test.stream().filter(s -> s.contains("a")).count();
        System.out.println(res);
        // 规约
        Optional<String> reduce = test.stream().reduce((a1, a2) -> a1 + "," + a2);
        reduce.ifPresent(System.out::println);

Date

   Clock clock = Clock.systemDefaultZone();
        System.out.println(clock.millis());
        System.out.println(clock.instant());
        System.out.println(Date.from(clock.instant()));

        // 时区
        System.out.println(ZoneId.getAvailableZoneIds());

        ZoneId zone1 = ZoneId.of("Asia/Aden");
        ZoneId zone2 = ZoneId.of("Brazil/East");
        ZoneId zone3 = ZoneId.of("Asia/Yerevan");
        System.out.println(zone1.getRules());
        System.out.println(zone2.getRules());
        System.out.println(zone3.getRules());

        LocalTime now1 = LocalTime.now(zone1);
        LocalTime now2 = LocalTime.now(zone2);
        LocalTime now = LocalTime.now();
        System.out.println(now2 + "," + now1 + "," + now);

        LocalDate today = LocalDate.now();
        System.out.println("today:"+today);
        LocalDate tomorrow = today.plus(1, ChronoUnit.DAYS);
        System.out.println(tomorrow);