java比较器Comparator的简单使用

 1 import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

public class ComparatorTest implements Comparator<stuEntity> {

    /**
     * @param args
     */
    public static void main(String[] args) {
        List<stuEntity> list = new ArrayList<stuEntity>();
        stuEntity stud1=new stuEntity();
        stud1.setAge(10);
        stud1.setName("abc");
        stuEntity stud2=new stuEntity();
        stud2.setAge(10);
        stud2.setName("bdc");
        stuEntity stud3=new stuEntity();
        stud3.setAge(5);
        stud3.setName("bdd");
        stuEntity stud4=new stuEntity();
        stud4.setAge(30);
        stud4.setName("aad");
        
        list.add(stud1);
        list.add(stud2);
        list.add(stud3);
        list.add(stud4);
        
        Collections.sort(list, new ComparatorTest());
        
        for(stuEntity stud:list){
            System.out.println(stud.getAge()+":"+stud.getName());
        }
    }
/**
 * 
 */
    @Override
    public int compare(stuEntity stud1, stuEntity stud2) {
        //根据姓名排序
        int maxname=stud1.getName().compareTo(stud2.getName());
        if(maxname!=0)
            return maxname;
        //根据年龄排序
        int maxage=stud1.getAge()-stud2.getAge();
        //if(maxage!=0)
            return maxage;
        
        
        
    }

}

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;
    }
}