JAVA对ArrayList排序
以下前三个代码都是通过实现Comparable接口，或是实例化一个比较器，虽然重点部分重复了，也各有不同，还是都贴上吧。
http://zhidao.baidu.com/question/97784478
java如何对ArrayList中对象按照该对象某属性排序
增加排序功能，打印时：输出学生对象的时候，需要先按照年龄排序，如果年龄相同，则按照姓名排序，如果姓名也相同，则按照学号排序。
Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/-->import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
public class ComparableTest {
public static void main(String[] args) {
Comparator comparator = new Comparator(){
public int compare(Student s1, Student s2) {
//先排年龄
if(s1.age!=s2.age){
return s1.age-s2.age;
}
else{
//年龄相同则按姓名排序
if(!s1.name.equals(s2.name)){
return s1.name.compareTo(s2.name);
}
else{
//姓名也相同则按学号排序
return s1.id-s2.id;
}
}
}
};
Student stu1 = new Student (1,"zhangsan","male",28,"cs");
Student stu2 = new Student (2,"lisi","female",19,"cs");
Student stu3 = new Student (3,"wangwu","male",22,"cs");
Student stu4 = new Student (4,"zhaoliu","female",17,"cs");
Student stu5 = new Student (5,"jiaoming","male",22,"cs");
ArrayList List = new ArrayList();
List.add(stu1);
List.add(stu2);
List.add(stu3);
List.add(stu4);
List.add(stu5);
//这里就会自动根据规则进行排序
Collections.sort(List,comparator);
display(List);
}
static void display(ArrayList lst){
for(Student s:lst)
System.out.println(s);
}
}
class Student{
int age;
int id;
String gender;
String name;
String cs;
Student(int id,String name,String gender,int age,String cs){
this.age=age;
this.name=name;
this.gender=gender;
this.id=id;
this.cs=cs;
}
public String toString(){
return id+" "+name+" "+gender+" "+age+" "+cs;
}
} 以一个point点类做例子：
以一个point点类做例子：
Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/-->import java.util.*;
public class Test {
public static void main(String[] args){
List points=new ArrayList();
Point point1=new Point();
point1.setX(1324);
point1.setY(345);
point1.setZ(436);
points.add(point1);
Point point2=new Point();
point2.setX(23);
point2.setY(8941.656);
point2.setZ(431412);
points.add(point2);
Point point3=new Point();
point3.setX(786584);
point3.setY(23452);
point3.setZ(43563);
points.add(point3);
//根据X排序
Collections.sort(points,new SortByX());
for(Point p:points){
System.out.print(p.getX()+"\t"+p.getY()+"\t"+p.getZ());
System.out.println();
}
//根据Y排序
// Collections.sort(points,new SortByY());
//
// for(Point p:points){
// System.out.print(p.getX()+"\t"+p.getY()+"\t"+p.getZ());
// System.out.println();
// }
//
// //根据Z排序
// Collections.sort(points,new SortByZ());
//
// for(Point p:points){
// System.out.print(p.getX()+"\t"+p.getY()+"\t"+p.getZ());
// System.out.println();
// }
}
}
class Point{
private double x;
private double y;
private double z;
public double getX() {
return x;
}
public void setX(double x) {
this.x = x;
}
public double getY() {
return y;
}
public void setY(double y) {
this.y = y;
}
public double getZ() {
return z;
}
public void setZ(double z) {
this.z = z;
}
public Point(){}
}
//根据X排序
class SortByX implements Comparator{
public int compare(Object obj1,Object obj2){
Point point1=(Point)obj1;
Point point2=(Point)obj2;
if(point1.getX()>point2.getX())
return 1;
else
return 0;
}
}
//根据Y排序
class SortByY implements Comparator{
public int compare(Object obj1,Object obj2){
Point point1=(Point)obj1;
Point point2=(Point)obj2;
if(point1.getY()>point2.getY())
return 1;
else
return 0;
}
}
//根据Z排序
class SortByZ implements Comparator{
public int compare(Object obj1,Object obj2){
Point point1=(Point)obj1;
Point point2=(Point)obj2;
if(point1.getZ()>point2.getZ())
return 1;
else
return 0;
}
} 结果:
1, aa
2, bb
3, cc
4, dd
5, ee //注意:同样是5岁的人，则比较名字(ee,ff)，然后排序
5, ff
6, ggCode highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/-->//一个POJO例子
class User {
String name;
String age;
public User(String name,String age){
this.name=name;
this.age=age;
}
public String getAge() {
return age;
}
public void setAge(String age) {
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
//具体的比较类，实现Comparator接口
import java.util.Comparator;
import java.util.List;
import java.util.ArrayList;
import java.util.Collections;
public class ComparatorUser implements Comparator{
public int compare(Object arg0, Object arg1) {
User user0=(User)arg0;
User user1=(User)arg1;
//首先比较年龄，如果年龄相同，则比较名字
int flag=user0.getAge().compareTo(user1.getAge());
if(flag==0){
return user0.getName().compareTo(user1.getName());
}else{
return flag;
}
}
}
//测试类
public class SortTest {
public static void main(String[] args){
List userlist=new ArrayList();
userlist.add(new User("dd","4"));
userlist.add(new User("aa","1"));
userlist.add(new User("ee","5"));
userlist.add(new User("bb","2"));
userlist.add(new User("ff","5"));
userlist.add(new User("cc","3"));
userlist.add(new User("gg","6"));
ComparatorUser comparator=new ComparatorUser();
Collections.sort(userlist, comparator);
for (int i=0;i最后这个没有用java的Comparable接口，自己写的排序函数。
要用JAVA写个东西读取TXT中的数据 且要计算出平均值和总值 最后还要按总值排序。 TXT的文件如下： 学号 姓名 语文 数学 英语 平均值 总值 排序 1 李守东 83 73 75 2 徐贤坤 58 58 87 3 钱云宋 41 86 90 4 陈平 83 43 65 5 金荣权 93 88 63 6 陈如棉 99 93 43 7 章可可 98 62 72 8 陈伟奔 87 43 76 9 张如祥 69 58 78 10 丁尚游 80 56 57 11 林宏旦 91 90 76 12 曾上腾 100 96 54 13 谢作品 82 100 55 14 温从卫 73 46 101 15 李明察 81 41 75 16 彭鸿威 46 46 89 17 翁文秀 57 43 58 18 陈家伟 63 58 98 19 温正考 100 64 57 20 周文湘 50 50 79 21 吴杰 65 65 83 22 赖登城 60 79 53 23 聂树露 51 76 45 24 张雅琴 68 95 56 25 曾瑞约 88 63 58 26 王志强 96 79 78 27 徐贤所 66 46 74 28 陈祥枭 82 96 91 29 温婷婷 41 73 96 30 应孔余 66 81 71 31 宋成取 71 68 62 32 黄益省 65 56 43 33 陈思文 55 100 44 34 上官福新 64 62 70 35 钟国横 49 69 56 36 林型涨 78 73 50
代码：
Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/-->import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class Testa
{
public static void main(String[] args)
{
//传入参数为文件目录
test("d:/a.txt");
}
public static void test(String filePath){
BufferedReader br = null;
try {
br = new BufferedReader(new FileReader(filePath));
} catch (FileNotFoundException e) {
e.printStackTrace();
return;
}
String []columnName = {"Id", "Name", "Languages", "Math", "English"}; //列名
int []courseIndexs = {2, 3, 4}; //课程对应的列
int i,j,index;
String line;
List> students = new ArrayList>();
//记录Id和总值,用于排序
List> sortList = new ArrayList>();
try {
br.readLine(); //去掉第一行
while((line = br.readLine()) != null){
index = 0;
String []se = line.split(" ");
Map student = new HashMap();
for(i = 0; i < se.length; i++){
if("".equals(se[i])){
continue;
}
if(index >= columnName.length){
continue;
}
student.put(columnName[index], se[i]);
index++;
}
//计算平均值,总值
double total = 0;
for(j = 0; j < courseIndexs.length; j++){
total += Double.parseDouble((String) student.get(columnName[courseIndexs[j]]));
}
double average = total / courseIndexs.length;
//只取一位小数
average = Math.round(average * 10)/10;
student.put("Total", total);
student.put("Average", average);
Map sort = new HashMap();
sort.put("Id", student.get("Id"));
sort.put("Total", student.get("Total"));
sortList.add(sort);
students.add(student);
}
br.close();
//选择排序
for(i = 0; i < sortList.size(); i++){
for(j = i + 1; j < sortList.size(); j++){
if((Double)sortList.get(i).get("Total") < (Double)sortList.get(j).get("Total")){
Map temp = sortList.get(i);
sortList.set(i, sortList.get(j));
sortList.set(j, temp);
}
}
}
Map sortedId = new HashMap();
for(i = 0; i < sortList.size(); i++){
sortedId.put(sortList.get(i).get("Id"), i+1);
}
//设定序号
for(j = 0; j < students.size(); j++){
students.get(j).put("Order", sortedId.get(students.get(j).get("Id")));
}
//输出(写到原文件)
//PrintWriter pw = new PrintWriter(new File(filePath));
//输出(写到其他文件)
PrintWriter pw = new PrintWriter(new File("D:/b.txt"));
pw.println("Id\tName\tLan\tMath\tEnglish\tAverage\tTotal\tSort");
int cIndex;
for(i = 0; i < students.size(); i++){
Map st = students.get(i);
cIndex = 0;
pw.println(st.get(columnName[cIndex++]) + "\t" + st.get(columnName[cIndex++])
+ "\t" + st.get(columnName[cIndex++])+ "\t" + st.get(columnName[cIndex++])
+ "\t" + st.get(columnName[cIndex++])
+ "\t" + st.get("Total")
+ "\t" + st.get("Average")
+ "\t" + st.get("Order"));
}
pw.flush();
pw.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}