stream流过滤对象中的属性，将对象中某些字段转化为map

最新推荐文章于 2024-12-05 16:34:34 发布

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最新推荐文章于 2024-12-05 16:34:34 发布

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分类专栏： stream流文章标签： java

本文链接：https://blog.youkuaiyun.com/jdaiwlsd/article/details/120758696

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该篇博客演示了Java Stream API的使用，包括如何过滤年龄大于24且名字长度大于3的学生，以及创建包含名字和年龄的Map。同时展示了将学生名单转换为列表的操作。涉及到的知识点包括Stream的filter、map和collect方法。

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package cn.dj.demo.test;

import cn.dj.demo.domain.Student;

import java.text.SimpleDateFormat;
import java.util.*;
import java.util.stream.Collectors;

public class TestStudent {
    public static void main(String[] args) {
        List<Student> studentList = new ArrayList<>();
        studentList.add(new Student(1,"张三","23",new Date(),1));
        studentList.add(new Student(1,"李四","24",new Date(),1));
        studentList.add(new Student(1,"张瘦瘦","25",new Date(),1));
        studentList.add(new Student(1,"李胖胖","26",new Date(),2));
        studentList.add(new Student(1,"上课萨拉","33",new Date(),3));

        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

        // 1.过滤年龄大于24的人 ，并且名字长度大于3的
        List<Student> collect = studentList.stream().filter(s -> Integer.valueOf(s.getSAge()) > 24)
                .filter(s -> s.getSName().length() > 3 )
                .collect(Collectors.toList());
        for (Student student : collect) {
            System.out.println(student);
        }
        System.out.println("------------");


        // 2. 获取学生名字和年龄的map ，并且是名字长度小于4的
        Map<String, String> map = studentList.stream().filter(s -> s.getSName().length() < 4)
                .collect(Collectors.toMap(Student::getSName, Student::getSAge));
        Set<Map.Entry<String, String>> entries = map.entrySet();
        entries.stream().forEach( i -> {
            System.out.println(i.getKey() + "--" + i.getValue());
        });
        System.out.println("-----------");


        List<String> nameList = studentList.stream().map(Student::getSName).collect(Collectors.toList());
        for (String s : nameList) {
            System.out.println(s);
        }
        System.out.println("-----------");


    }
}






package cn.dj.demo.domain;

import com.fasterxml.jackson.annotation.JsonFormat;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import org.springframework.format.annotation.DateTimeFormat;

import java.util.Date;

@Data
@AllArgsConstructor
@NoArgsConstructor
public class Student {

    private Integer sId;
    private String sName;
    private String sAge;
    private Date sBirthday;
    private Integer sClass;

}


<dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.4</version>
        </dependency>