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  • Java8 使用 stream().map()提取List对象的某一列值及排重

    List对象类(StudentInfo)

    public class StudentInfo implements Comparable<StudentInfo> {
    
        //名称
        private String name;
    
        //性别 true男 false女
        private Boolean gender;
    
        //年龄
        private Integer age;
    
        //身高
        private Double height;
    
        //出生日期
        private LocalDate birthday;
    
        public StudentInfo(String name, Boolean gender, Integer age, Double height, LocalDate birthday){
            this.name = name;
            this.gender = gender;
            this.age = age;
            this.height = height;
            this.birthday = birthday;
        }
    
        public String toString(){
            String info = String.format("%s		%s		%s			%s		%s",this.name,this.gender.toString(),this.age.toString(),this.height.toString(),birthday.toString());
            return info;
        }
    
        public static void printStudents(List<StudentInfo> studentInfos){
            System.out.println("[姓名]		[性别]		[年龄]		[身高]		[生日]");
            System.out.println("----------------------------------------------------------");
            studentInfos.forEach(s->System.out.println(s.toString()));
            System.out.println(" ");
        }
    
        @Override
        public int compareTo(StudentInfo ob) {
            return this.age.compareTo(ob.getAge());
            //return 1;
        }
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        public Boolean getGender() {
            return gender;
        }
    
        public void setGender(Boolean gender) {
            this.gender = gender;
        }
    
        public Integer getAge() {
            return age;
        }
    
        public void setAge(Integer age) {
            this.age = age;
        }
    
        public Double getHeight() {
            return height;
        }
    
        public void setHeight(Double height) {
            this.height = height;
        }
    
        public LocalDate getBirthday() {
            return birthday;
        }
    
        public void setBirthday(LocalDate birthday) {
            this.birthday = birthday;
        }
    }
    StudentInfo对象类

    测试数据

    //测试数据,请不要纠结数据的严谨性
    List<StudentInfo> studentList = new ArrayList<>();
    studentList.add(new StudentInfo("李小明",true,18,1.76,LocalDate.of(2001,3,23)));
    studentList.add(new StudentInfo("张小丽",false,18,1.61,LocalDate.of(2001,6,3)));
    studentList.add(new StudentInfo("王大朋",true,19,1.82,LocalDate.of(2000,3,11)));
    studentList.add(new StudentInfo("陈小跑",false,17,1.67,LocalDate.of(2002,10,18)));

    提取某一列(以name为例)

     //输出List
    StudentInfo.printStudents(studentList);
    //从对象列表中提取一列(以name为例)
    List<String> nameList = studentList.stream().map(StudentInfo::getName).collect(Collectors.toList());
    //提取后输出name
    nameList.forEach(s-> System.out.println(s));

    输出结果如下图:

     提取age列并排重(使用distinct()函数)

    //提取前输出
    StudentInfo.printStudents(studentList);
    //从对象列表中提取age并排重
    List<Integer> ageList = studentList.stream().map(StudentInfo::getAge).distinct().collect(Collectors.toList());
    ageList.forEach(a-> System.out.println(a));

    结果如下图:

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  • 原文地址:https://www.cnblogs.com/codecat/p/10903936.html
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