Java8 使用 stream().sorted()对List集合进行排序

集合对像定义

集合对象以学生类(StudentInfo)为例,有学生的基本信息,包括:姓名,性别,年龄,身高,生日几项。

使用stream().sorted()进行排序,需要该类实现 Comparable 接口,该接口只有一个方法需要实现,如下:

public int compareTo(T o);

有关compareTo方法的实现说明,请参考:Java 关于重写compareTo方法

我的学生类代码如下:

import java.time.LocalDate;
import java.util.List;

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;
    }
}
StudentInfo对象类

添加测试数据

下面来添加一些测试用的数据,代码如下:

//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)));

 排序

使用年龄进行升序排序

//排序前输出
StudentInfo.printStudents(studentList);
//按年龄排序(Integer类型)
List<StudentInfo> studentsSortName = studentList.stream().sorted(Comparator.comparing(StudentInfo::getAge)).collect(Collectors.toList());
//排序后输出
StudentInfo.printStudents(studentsSortName);

结果如下图:

 使用年龄进行降序排序(使用reversed()方法)

//排序前输出
StudentInfo.printStudents(studentList);
//按年龄排序(Integer类型)
List<StudentInfo> studentsSortName = studentList.stream().sorted(Comparator.comparing(StudentInfo::getAge).reversed()).collect(Collectors.toList());
//排序后输出
StudentInfo.printStudents(studentsSortName);

结果如下图:

 使用年龄进行降序排序,年龄相同再使用身高升序排序

//排序前输出
        StudentInfo.printStudents(studentList);
        //按年龄排序(Integer类型)
        List<StudentInfo> studentsSortName = studentList.stream()
                .sorted(Comparator.comparing(StudentInfo::getAge).reversed().thenComparing(StudentInfo::getHeight))
                .collect(Collectors.toList());
        //排序后输出
        StudentInfo.printStudents(studentsSortName);

结果如下图:

posted @ 2019-05-21 14:13  代码猫  阅读(173206)  评论(7编辑  收藏  举报