java比较器Comparator的简单使用

 1 import java.util.ArrayList;

 2 import java.util.Collections;

 3 import java.util.Comparator;

 4 import java.util.List;

 5 

 6 public class ComparatorTest implements Comparator<stuEntity> {

 7 

 8     /**

 9      * @param args

10      */

11     public static void main(String[] args) {

12         List<stuEntity> list = new ArrayList<stuEntity>();

13         stuEntity stud1=new stuEntity();

14         stud1.setAge(10);

15         stud1.setName("abc");

16         stuEntity stud2=new stuEntity();

17         stud2.setAge(10);

18         stud2.setName("bdc");

19         stuEntity stud3=new stuEntity();

20         stud3.setAge(5);

21         stud3.setName("bdd");

22         stuEntity stud4=new stuEntity();

23         stud4.setAge(30);

24         stud4.setName("aad");

25         

26         list.add(stud1);

27         list.add(stud2);

28         list.add(stud3);

29         list.add(stud4);

30         

31         Collections.sort(list, new ComparatorTest());

32         

33         for(stuEntity stud:list){

34             System.out.println(stud.getAge()+":"+stud.getName());

35         }

36     }

37 /**

38  * 

39  */

40     @Override

41     public int compare(stuEntity stud1, stuEntity stud2) {

42         //根据姓名排序

43         int maxname=stud1.getName().compareTo(stud2.getName());

44         if(maxname!=0)

45             return maxname;

46         //根据年龄排序

47         int maxage=stud1.getAge()-stud2.getAge();

48         //if(maxage!=0)

49             return maxage;

50         

51         

52         

53     }

54 

55 }

输出：

30:aad
10:abc
10:bdc
5:bdd

java的比较器很有用，实现Comparator接口的compare（）这个回调方法来制定排序规则，然后调用Collections.sort(list, new ComparatorTest());就可以将List进行排序，很方便

使用时要注意compare（）方法中的return的先后顺序，优先的排序规则要写在前面

实体类：

/**

 * 学生实体类

 * 

 */

public class stuEntity {

    private int studentId;// 学号

    private String name;

    private int age;

    private String sex;// 性别

    private int roomNumber;// 房间号

    private String degree;//学位

    private int grade;//年级

    private String deviceNumber;// 设备号

    private int groupNumber;// 所属的小组

    private int javaScore;// java成绩

    private int netScore;// NET成绩

    public String getDegree() {

        return degree;

    }



    public void setDegree(String degree) {

        this.degree = degree;

    }



    public int getGrade() {

        return grade;

    }



    public void setGrade(int grade) {

        this.grade = grade;

    }







    /**

     * 初始化有参构造函数

     * 

     * @param id

     * @param name

     * @param age

     * @param sex

     * @param roomNumber

     * @param deviceNumber

     * @param groupNumber

     * @param javaScore

     * @param netScore

     */

    public stuEntity(String name, int age, String sex, int roomNumber,

            String deviceNumber, int groupNumber, int javaScore, int netScore) {

        this.name = name;

        this.age = age;

        this.sex = sex;

        this.roomNumber = roomNumber;

        this.deviceNumber = deviceNumber;

        this.groupNumber = groupNumber;

        this.javaScore = javaScore;

        this.netScore = netScore;

    }



    /**

     * 无参构造函数

     */

    public stuEntity() {



    }



    public int getJavaScore() {

        return javaScore;

    }



    public void setJavaScore(int javaScore) {

        this.javaScore = javaScore;

    }



    public int getNetScore() {

        return netScore;

    }



    public void setNetScore(int netScore) {

        this.netScore = netScore;

    }



    



    public int getStudentId() {

        return studentId;

    }



    public void setStudentId(int studentId) {

        this.studentId = studentId;

    }



    public String getName() {

        return name;

    }



    public void setName(String name) {

        this.name = name;

    }



    public int getAge() {

        return age;

    }



    public void setAge(int age) {

        this.age = age;

    }



    public String getSex() {

        return sex;

    }



    public void setSex(String sex) {

        this.sex = sex;

    }



    public int getRoomNumber() {

        return roomNumber;

    }



    public void setRoomNumber(int roomNumber) {

        this.roomNumber = roomNumber;

    }



    public String getDeviceNumber() {

        return deviceNumber;

    }



    public void setDeviceNumber(String deviceNumber) {

        this.deviceNumber = deviceNumber;

    }



    public int getGroupNumber() {

        return groupNumber;

    }



    public void setGroupNumber(int groupNumber) {

        this.groupNumber = groupNumber;

    }

}