java8分组+拼接字段代替数据库groupby+group_concat（）
最近在写⼀个需求分组后拼接字段，在页⾯展⽰。我本在sql层⾯实现了，⽤的group by分组    group_concat函数拼接字段。但是被reivew时被告知不能⽤group_concat函数，复杂操作需要业务层进⾏。就写了java去实现 group by + group_concat的功能
业务场景脱敏后如下：
根据姓名分组，分组后多个年龄和爱好⽤“，”拼接
public static void main(String[] args) {
List<Student> list = new ArrayList<>();
Student a = new Student("张三", "12", "⾜球");
Student b = new Student("张三", "16", "篮球");
Student c = new Student("王五", "17", "排球");
Student d = new Student("李四", "13", "⽪球");
Student e = new Student("王五", "12", "⽔球");
list.add(a);
list.add(b);
list.add(c);
list.add(d);
list.add(e);
List<Student> stList = list.stream()
.collect(groupingBy(Student::getName))
.entrySet()
.stream()
.map(stEntity -> {
/
/ 去重⽤set即可
List<String> ages = new ArrayList<>();
List<String> hobbys = new ArrayList<>();
.peek(st -> ages.Age()))
.forEach(st -> hobbys.Hobby()));
return new Key(),
String.join(",", ages),
String.join(",", hobbys));
})
.List());
System.out.println(stList);
}
}
class Student{
private String name;
private String age;
private String hobby;
public Student(String name, String age, String hobby) {
this.name = name;
this.age = age;
this.hobby = hobby;
}
public String getName() {
return name;groupby分组
}
public String getAge() {
return age;
}
public String getHobby() {
return hobby;
}
@Override
@Override
public String toString() {
return "Student{" +
"name='" + name + '\'' +                ", age=" + age +
", hobby='" + hobby + '\'' +                '}';
}
结果如下：