JDK1.8 stream 属性使用

最新推荐文章于 2023-11-30 19:17:35 发布

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本文介绍了如何使用Java 8的Stream API处理Student对象列表，包括筛选班级为2的学员、转换为Map、列表循环和分组等操作，展示了Stream API在数据处理中的强大功能。

public class Student {

    private Long stuId;
    private String stuName;
    private Integer age;
    private String stuCar;
    private Integer stuClass;

}



public class RedisTest {

    public static void main(String[]age){
        
        Student st1 = new Student();
        st1.setStuId(1l);
        st1.setAge(1);
        st1.setStuName("cui1");
        st1.setStuCar("111");
        st1.setStuClass(1);

        Student st2 = new Student();
        st2.setStuId(2l);
        st2.setAge(2);
        st2.setStuName("cui2");
        st2.setStuCar("222");
        st2.setStuClass(1);

        Student st3 = new Student();
        st3.setStuId(3l);
        st3.setAge(3);
        st3.setStuName("cui3");
        st3.setStuCar("333");
        st3.setStuClass(2);

        Student st4 = new Student();
        st4.setStuId(4l);
        st4.setAge(4);
        st4.setStuName("cui4");
        st4.setStuCar("4444");
        st4.setStuClass(2);

        Student st5 = new Student();
        st5.setStuId(5l);
        st5.setAge(5);
        st5.setStuName("cui5");
        st5.setStuCar("55");
        st5.setStuClass(3);


        List<Student> stList = new ArrayList<>();
        stList.add(st1);
        stList.add(st2);
        stList.add(st3);
        stList.add(st4);
        stList.add(st5);

        listToMap(stList);
        System.out.println("---------------1");
        foreachList(stList);

        System.out.println("---------------2");

        ListToObjectMap(stList);

        System.out.println("---------------3");

        listTofilter(stList);

        System.out.println("---------------4");

        listToMapList(stList);

    }

    /**
     * 只要班级为2班的学生
     * list filter过滤
     * @param stList
     */
    public static void listTofilter(List<Student> stList){
        List<Student>  listType =  stList.stream().filter(t->t.getStuClass()==2).collect(Collectors.toList());
        listType.forEach(item->{
            System.out.println(item.getStuName());
        });
    }

    /**
     * list转map 对象
     * @param stList
     */
    public static  void ListToObjectMap(List<Student> stList){
        Map<Long,Student>  stuMap = stList.stream().collect(Collectors.toMap(Student::getStuId,Student->Student));
        stuMap.forEach((k,v)->{
            System.out.println(k+"--"+v.getStuName());
        });
    }

    /**
     * list转map
     * @param stList
     */
    public static void listToMap(List<Student> stList){
        Map<Long,String> map = stList.stream().collect(Collectors.toMap(Student::getStuId,Student::getStuName));
        map.forEach((k,v)->{
            System.out.println("Item : " + k + " Count : " + v);
        });
    }

    /**
     * list 循环
     * @param stList
     */
    public static void foreachList(List<Student> stList){
        stList.forEach(a->{
            System.out.println(a.getStuId());
        });
    }

    /**
     * list 分组
     * @param stuList
     */
    public static void listToMapList(List<Student> stuList){

        Map<Integer,List<Student>> s = stuList.stream().collect(Collectors.groupingBy(obj->obj.getStuClass()));
        s.forEach((k,v)->{
            System.out.println("k--"+k+"---"+v.size());
        });

    }

}

编写了jdk1.8 stream() 常用属性