Stream流

Stream流中间方法

public class Demo01 {
    public static void main(String[] args) {
        Student s1 = new Student("蜘蛛精", 26, 172.5);
        Student s2 = new Student("蜘蛛精", 26, 172.5);
        Student s3 = new Student("紫霞", 23, 167.6);
        Student s4 = new Student("白晶晶", 25, 169.0);
        Student s5 = new Student("牛魔王", 35, 183.3);
        Student s6 = new Student("牛夫人", 34, 168.5);
        List<Student> list = new ArrayList<>();
        Collections.addAll(list,s1,s2,s3,s4,s5,s6);

        //filter 过滤  
        //sort 排序
        list.stream().
                filter(student -> student.getHeight() > 170).
                sorted(Comparator.comparing(Student::getAge)).
                forEach(student -> System.out.println(student));

        System.out.println("-----------------------------------");

        list.stream().filter(student -> student.getAge() > 30)
                .sorted((o1, o2) -> o2.getAge() - o1.getAge())
                .forEach(student -> System.out.println(student));

        System.out.println("-------------------------");

       //limit 获取前几个元素
       list.stream().sorted((o1, o2) -> Double.compare(o2.getHeight(),o1.getHeight()))
               .limit(3)
               .forEach(student -> System.out.println(student));
        System.out.println("----------------------------------------------");

        //skip 跳过前几个元素
        list.stream().sorted((o1, o2) -> Double.compare(o2.getHeight(),o1.getHeight()))
                .skip(list.size()-2)
                .forEach(student -> System.out.println(student));
        System.out.println("----------------------------------------------");

        //distinct 去除重复元素
       list.stream().filter(student -> student.getHeight()>170)
               .map(student -> student.getHeight())
               .distinct()
               .forEach(student -> System.out.println(student));
        System.out.println("----------------------------------------------");


        //concat 连接两个流
        Stream<String> stream1 = Stream.of("阿大", "阿二");
        Stream<String> stream2 = Stream.of("阿三", "阿四");
        Stream.concat(stream1,stream2).forEach(student -> System.out.println(student));
    }
}

Stream流终结方法

public class Demo02 {
    public static void main(String[] args) {
        Student s1 = new Student("蜘蛛精", 26, 172.5);
        Student s2 = new Student("蜘蛛精", 26, 172.5);
        Student s3 = new Student("紫霞", 23, 167.6);
        Student s4 = new Student("白晶晶", 25, 169.0);
        Student s5 = new Student("牛魔王", 35, 183.3);
        Student s6 = new Student("牛夫人", 34, 168.5);
        List<Student> list = new ArrayList<>();
        Collections.addAll(list,s1,s2,s3,s4,s5,s6);

        //count 统计元素个数
        System.out.println(list.stream().filter(student -> student.getHeight() < 170).count());
        //max 获取最大值
        System.out.println(list.stream().max((o1, o2) -> Double.compare(o1.getHeight(),o2.getHeight())).get());

        //min 获取最小值
        System.out.println(list.stream().min(Comparator.comparingDouble(Student::getHeight)).get());

        System.out.println("__________________________________________");

        //collect 将Stream流中的元素收集到一个集合中
        System.out.println(list.stream().filter(student -> student.getAge() > 30).collect(Collectors.toList()));
        System.out.println(list.stream().filter(student -> student.getAge() < 30).collect(Collectors.toSet()));

        System.out.println("----------------------------------------------");
        list.stream().filter(student -> student.getAge() > 30)
                .collect(Collectors.toMap(student -> student.getName(), student -> student.getHeight()))
                .forEach((s, aDouble) -> System.out.println("key="+s+",value="+aDouble));
    }
}