作业票list使用stream更据作业票id进行分类

假设我们有一个作业票类，其属性包括id、姓名、状态等。

首先我们需要创建一个作业票的列表：

List<HomeworkTicket> homeworkTicketList = new ArrayList<>();

然后我们可以使用stream对其进行分类：

Map<String, List<HomeworkTicket>> groupedHomeworkTicketList = homeworkTicketList.stream()
.collect(Collectors.groupingBy(HomeworkTicket::getId));

这段代码会将homeworkTicketList按照id进行分类，并返回一个Map，其中key为id，value为对应id的作业票列表。

完整代码如下：

import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

public class HomeworkTicket {
private String id;
private String name;
private String status;

public HomeworkTicket(String id, String name, String status) {
this.id = id;
this.name = name;
this.status = status;
}

public String getId() {
return id;
}

public String getName() {
return name;
}

public String getStatus() {
return status;
}

public static void main(String[] args) {
List<HomeworkTicket> homeworkTicketList = new ArrayList<>();
homeworkTicketList.add(new HomeworkTicket("1", "张三", "已完成"));
homeworkTicketList.add(new HomeworkTicket("1", "李四", "已完成"));
homeworkTicketList.add(new HomeworkTicket("2", "王五", "未完成"));
Map<String, List<HomeworkTicket>> groupedHomeworkTicketList = homeworkTicketList.stream()
.collect(Collectors.groupingBy(HomeworkTicket::getId));
System.out.println(groupedHomeworkTicketList);
}
}

输出结果：

{1=[HomeworkTicket@2f4d3709, HomeworkTicket@7440e464], 2=[HomeworkTicket@49476842]}