java8最简单的list列表转换成map类型

傷城~ 2022-03-28 10:26 512阅读 0赞

list列表转换成map结构

方法一：

Map<Integer, Student> mapStream = studentList.stream().collect(Collectors.toMap(Student::getNumber, Student -> Student));

方法二：

Map<Integer, Student> studentMap = new HashMap<>();
    studentList.forEach(a -> studentMap.put(a.getNumber(), a));

具体实例：

import model.Student;
    
    import java.util.ArrayList;
    import java.util.HashMap;
    import java.util.List;
    import java.util.Map;
    import java.util.stream.Collectors;
    
    /**
     * @author : null
     * @date : 2019/1/10
     * @description:
     */
    public class ListToMap {
        public static void main(String[] args) {
            List<Student> studentList = new ArrayList<>();
            Student student = new Student();
            student.setName("第一位");
            student.setNumber(1);
            studentList.add(student);
            Student student1 = new Student();
            student1.setNumber(2);
            student1.setName("第二位");
            studentList.add(student1);
    
            //方法一
            Map<Integer, Student> mapStream = studentList.stream().collect(Collectors.toMap(Student::getNumber, Student -> Student));
            System.out.println(mapStream.get(1).getName());
            System.out.println(mapStream.get(2).getName());
    
            System.out.println("+++++++++++++++++分割线+++++++++++++++++++++");
            //方法二
            Map<Integer, Student> studentMap = new HashMap<>();
            studentList.forEach(a -> studentMap.put(a.getNumber(), a));
            System.out.println(studentMap.get(1).getName());
            System.out.println(studentMap.get(2).getName());
        }
    }

附属类

/**
     * @author : null
     * @date : 2018/11/20
     * @description:
     */
    public class Student{
    
        private String name;
        private Integer number;
        private Teacher teacher;
    
        public Teacher getTeacher() {
            return teacher;
        }
    
        public void setTeacher(Teacher teacher) {
            this.teacher = teacher;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        public String getName() {
            return name;
        }
    
        public Integer getNumber() {
            return number;
        }
    
        public void setNumber(Integer number) {
            this.number = number;
        }
    }

输出结果：

第一位
    第二位
    +++++++++++++++++分割线+++++++++++++++++++++
    第一位
    第二位