用java的stream工具，对一个对象类型的list，按某个属性分组，对另外一个属性用逗号拼接字符串。举例：我提供了一个List<Student>集合，按sex属性汇总name属性，输出一个List,list中具体的成员值为,sex="男",name="张三,李四"；第二个成员值为，sex="女",name="王五,赵六,黄七"

可以通过如下代码实现：

import java.util.*;
import java.util.stream.*;

public class GroupingAndJoining {
    public static void main(String[] args) {
        List<Student> students = Arrays.asList(
            new Student("男", "张三"),
            new Student("男", "李四"),
            new Student("女", "王五"),
            new Student("女", "赵六"),
            new Student("女", "黄七")
        );
        
        Map<String, List<Student>> groupedStudents = students.stream()
            .collect(Collectors.groupingBy(Student::getSex));
        
        List<Student> resultList = new ArrayList<>();
        for (Map.Entry<String, List<Student>> entry : groupedStudents.entrySet()) {
            String sex = entry.getKey();
            List<String> names = entry.getValue().stream()
                .map(Student::getName)
                .collect(Collectors.toList());
            resultList.add(new Student(sex, String.join(",", names)));
        }
        
        System.out.println(resultList);
    }
}

class Student {
    private String sex;
    private String name;
    
    public Student(String sex, String name) {
        this.sex = sex;
        this.name = name;
    }
    
    public String getSex() {
        return sex;
    }
    
    public String getName() {
        return name;
    }
    
    public String toString() {
        return "sex=\"" + sex + "\", name=\"" + name + "\"";
    }
}

输出结果为：

[sex="男", name="张三,李四", sex="女", name="王五,赵六,黄七"]