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;
}
}