1.9 Java1.8 Stream流应用 排序

Stream通道流支持两种排序方式：sorted()自然排序；sorted(Comparator comp)。

sorted()自然排序：产生一个新流，流中每个序列按自然排序的方式进行排序。 sorted(Comparator comp)：产生一个新流，流中的每个序列按自定义的比较器排序进行排序

一、sorted()

public static void main(String[] args) throws InterruptedException {
        List<String> list1 = new ArrayList<>();
        list1.add("2");
        list1.add("1");
        list1.add("3");
        Stream<String> stream1 = list1.stream().sorted();
        stream1.forEach(p -> System.out.println(p));
    }

输出结果

1
2
3

二、sorted(Comparator comp)

public static void main(String[] args) throws InterruptedException {
        List<Order> list = new ArrayList<>();
        Order order1 = new Order(LocalDateTime.now(), 1);
        Thread.sleep(2000);
        Order order2 = new Order(LocalDateTime.now(), 2);
        Thread.sleep(2000);
        Order order3 = new Order(LocalDateTime.now(), 3);
        Thread.sleep(2000);
        Order order4 = new Order(LocalDateTime.now(), 4);
        list.add(order2);
        list.add(order1);
        list.add(order3);
        list.add(order4);
        Stream<Order> stream = list.stream().sorted((o1, o2) -> {
            if (o1.getOrderTime().toInstant(ZoneOffset.of("+8")).toEpochMilli() - o2.getOrderTime().toInstant(ZoneOffset.of("+8")).toEpochMilli() >= 0) {
                return o1.getOrderTime().compareTo(o2.getOrderTime());
            } else {
                return o1.getOrderTime().compareTo(o2.getOrderTime());
            }
        });
        stream.forEach(p -> System.out.println(p));
    }

输出结果

Order{orderTime=2018-08-09T15:59:28.458, orderId=1}
Order{orderTime=2018-08-09T15:59:30.460, orderId=2}
Order{orderTime=2018-08-09T15:59:32.461, orderId=3}
Order{orderTime=2018-08-09T15:59:34.461, orderId=4}

三、获取排序的第一个元素

public static void main(String[] args) throws InterruptedException {
        List<Order> list = new ArrayList<>();
        Order order1 = new Order(LocalDateTime.now(), 1);
        Thread.sleep(2000);
        Order order2 = new Order(LocalDateTime.now(), 2);
        Thread.sleep(2000);
        Order order3 = new Order(LocalDateTime.now(), 3);
        Thread.sleep(2000);
        Order order4 = new Order(LocalDateTime.now(), 4);
        list.add(order2);
        list.add(order1);
        list.add(order3);
        list.add(order4);
        Stream<Order> stream = list.stream().sorted((o1, o2) -> {
            if (o1.getOrderTime().toInstant(ZoneOffset.of("+8")).toEpochMilli() - o2.getOrderTime().toInstant(ZoneOffset.of("+8")).toEpochMilli() >= 0) {
                return o1.getOrderTime().compareTo(o2.getOrderTime());
            } else {
                return o1.getOrderTime().compareTo(o2.getOrderTime());
            }
        });
        Optional<Order> first = stream.findFirst();
        System.out.println(first);
        Order order = first.get();
        System.out.println(order);
    }

输出结果

Optional[Order{orderTime=2018-08-09T16:47:26.415, orderId=1}]
Order{orderTime=2018-08-09T16:47:26.415, orderId=1}

转载 https://blog.csdn.net/qinaye/article/details/81539899