lambda分组后获取每组第一条数据

最新推荐文章于 2024-09-18 09:21:12 发布

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最新推荐文章于 2024-09-18 09:21:12 发布

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分类专栏： java8 Lambda表达式的使用

本文链接：https://blog.youkuaiyun.com/qq_34557770/article/details/96487576

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本文介绍了一个使用Java Stream API进行数据分组的示例，通过一个Employee类实例展示了如何根据员工职位进行分组并获取各组中第一个元素。

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collect(groupingBy(Employee::getRank, Collectors.collectingAndThen(Collectors.toList(), value -> value.get(0))))

import com.google.common.collect.Lists;

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

import static java.util.stream.Collectors.groupingBy;

public class Test {
    public static void main(String[] args) {
        Employee employee1 = new Employee("松皇","总经理","100000000000");
        Employee employee2 = new Employee("小赵","助理","100000");
        Employee employee3 = new Employee("小智","打杂","20000");
        Employee employee4 = new Employee("小李","打杂","20000");
        ArrayList<Employee> employees = Lists.newArrayList(employee1, employee2, employee3, employee4);
        Map<String, Employee> collect =
                employees.stream().collect(groupingBy(Employee::getRank, Collectors.collectingAndThen(Collectors.toList(), value -> value.get(0))));
        System.out.println(collect);
    }
}

import lombok.AllArgsConstructor;
import lombok.Data;

@Data
@AllArgsConstructor
public class Employee {
    private String name;
    private String rank;
    private String salary;
}