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\t\t%s\t\t%s\t\t\t%s\t\t%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]\t\t[性别]\t\t[年龄]\t\t[身高]\t\t[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;

}

}

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：