/** * Collection下的 stream()顺序流 和 parallelStream()并行流 方法 */List<String> list = new ArrayList<>();//获取一个顺序流Stream<String> stream = list.stream(); //获取一个并行流Stream<String> parallelStream = list.parallelStream(); /** * Arrays 中的stream()方法，将数组转成流 */Stream<Integer> arrayStream = Arrays.stream(new Integer[10]);/** * Stream中的静态方法：of()、iterate()、generate() */Stream<Integer> ofStream = Stream.of(1,2,3,4,5,6);Stream<Integer> iterateStream = Stream.iterate(0, (x) -> x + 2).limit(6);Stream<Double>  generateStream = Stream.generate(Math::random).limit(2);/** * BufferedReader.lines() 方法，将每行内容转成流 */BufferedReader reader = new BufferedReader(new FileReader("F:\\test_stream.txt"));Stream<String> fileStream = reader.lines();/** * 使用 Pattern.splitAsStream() 方法，将字符串分隔成流 */Pattern pattern = Pattern.compile(",");Stream<String> stringStream = pattern.splitAsStream("a,b,c,d");

private static List<Student> getList(){        List<Student> list = new ArrayList<Student>();        list.add(new Student("Tom", 17,Student.SubjectEnum.SX, 77));        list.add(new Student("Tom", 17,Student.SubjectEnum.YW, 87));
        list.add(new Student("Jack", 18,Student.SubjectEnum.SX, 87));        list.add(new Student("Jack", 18,Student.SubjectEnum.YY, 77));
        list.add(new Student("Lily", 17,Student.SubjectEnum.SX, 97));        list.add(new Student("Lily", 17,Student.SubjectEnum.YW, 77));
        list.add(new Student("Owen", 16,Student.SubjectEnum.SX, 87));        list.add(new Student("Anni", 16,Student.SubjectEnum.YW, 97));        list.add(new Student("Alisa", 20,Student.SubjectEnum.YY, 65));        return list;    }
    public static void main(String[] args) {        List<Student> list = getList();        //查找是否有 大于17的学生        boolean anyMatch= list.stream()                .anyMatch(s -> (s.getAge() > 17));//转list        System.out.println("找是否有 大于17的学生："+anyMatch);// true
        List<String> nameList=list.stream()                .filter(s -> (s.getAge() > 17)).map(Student::getName).collect(Collectors.toList());//转list        System.out.println("年龄大于17的学生："+nameList);// [Jack, Jack, Alisa]
        Student max = list.stream().max(Comparator.comparingInt(Student::getAge)).get();        System.out.println("年龄最大的学生：" + max.getName());//输出 Alisa;
        Student min = list.stream().min(Comparator.comparingInt(Student::getAge)).get();        System.out.println("年龄最小的学生：" + min.getName());//输出 Owen;        long count = list.stream().filter(s -> s.getSubject() == Student.SubjectEnum.SX).count();        System.out.println("学科数学中学生数量 ：" + count);//输出 4;
        //分数之和        Optional<Integer> sumSalary = list.stream().map(Student::getScore).reduce((s1,s2)->s1+s2);        Optional<Integer> sumSalary1 = list.stream().map(Student::getScore).reduce(Integer::sum);        System.out.println("分数之和 方式1：" + sumSalary.get());//输出 751;        System.out.println("分数之和 方式2：" + sumSalary1.get());//输出 751;
        // 求总数        Long count1 = list.stream().collect(Collectors.counting());        // 求平均工资        Double average = list.stream().collect(Collectors.averagingDouble(Student::getScore));        // 求最高工资        Optional<Integer> max1 = list.stream().map(Student::getScore).collect(Collectors.maxBy(Integer::compare));        // 求工资之和        Integer sum = list.stream().collect(Collectors.summingInt(Student::getScore));        // 一次性统计所有信息        DoubleSummaryStatistics collect = list.stream().collect(Collectors.summarizingDouble(Student::getScore));
        System.out.println("分数记录数：" + count);//4        System.out.println("平均每人每科分数：" + average);//83.44444444444444        System.out.println("分数总和：" + sum);//751        System.out.println("分数所有统计：" + collect);//DoubleSummaryStatistics{count=9, sum=751.000000, min=65.000000, average=83.444444, max=97.000000}
        // 将员工按薪资是否高于8000分组        Map<Boolean, List<Student>> part = list.stream().collect(Collectors.partitioningBy(x -> x.getScore() > 80));        System.out.println("分数大于80是分组情况：" + part);        // 将员工先按性别分组，再按地区分组        Map<Student.SubjectEnum, Map<Integer, List<Student>>> group2 = list.stream().collect(Collectors.groupingBy(Student::getSubject, Collectors.groupingBy(Student::getAge)));        System.out.println("按学科、年龄：" + group2);
        // 按工资倒序排序        List<String> newList2 = list.stream().sorted(Comparator.comparing(Student::getScore).reversed())                .map(Student::getName).collect(Collectors.toList());        // 先按工资再按年龄升序排序        List<String> newList3 = list.stream()                .sorted(Comparator.comparing(Student::getScore).thenComparing(Student::getAge)).map(Student::getName)                .collect(Collectors.toList());        System.out.println("分数倒序：" + newList2);        System.out.println("先按分数再按年龄升序排序：" + newList3);    }