//我使用java程序读取文本文件（athlete.txt）并将内容输出到
在屏幕上，我现在需要编写一个java程序，按运动员编号读取Athle.txt并对其进行排序（然后在屏幕上打印数据。输出可以按升序或降序排列。
import java.io.*;
import java.util.Scanner;
public class AthleteRecords {
public static void main(String[] args) throws Exception
{
Scanner in = new Scanner(new FileReader("athlete.txt"));
while (in.hasNextLine())
{
System.out.println(in.nextLine());
}
}
}
//Output file
Athlete Number: 4233
First Name: Peter
Family Name: Brown
Class 1
Position and points awarded for 100m race: 3 50
Position and points awarded for 200m race: 2 80
Position and points awarded for 400m race: 1 100
Class 2
Position and points awarded for 100m race: 3 50
Position and points awarded for 200m race: 4 20
Position and points awarded for 400m race: 2 80
Athlete Number: 1235
First Name: Robert
Family Name: Anderson
Class 1
Position and points awarded for 100m race: 4 20
Position and points awarded for 200m race: 1 100
Position and points awarded for 400m race: 2 80
Class 2
Position and points awarded for 100m race: 2 80
Position and points awarded for 200m race: 1 100
Position and points awarded for 400m race: 3 50
Athlete Number: 3248
First Name: Sean
Family Name: Thompson
Class 1
Position and points awarded for 100m race: 4 20
Position and points awarded for 200m race: 1 100
Position and points awarded for 400m race: 2 80
Class 2
Position and points awarded for 100m race: 2 80
Position and points awarded for 200m race: 1 100
Position and points awarded for 400m race: 3 50
答案 0 :(得分：0)
首先，我创建一个Athlete类，其中包含您需要的所有信息，如下所示：
public class Athlete {
private int id;
private String firstName;
private String lastName;
private List<Race> class1Races;
private List<Race> class2Races;
public Athlete() {
class1Races = new ArrayList<>(4);
class2Races = new ArrayList<>(4);
}
public int getId() {
return id;
}
//...probably more getters, if you need them elsewhere.
@Override
public String toString() {
String idString = Integer.toString(id);
StringBuilder result = new StringBuilder(60 + idString.length() + firstName.length() + lastName.length() + 52*class1Races.size() + 52*class2Races.size());
result.append("Athlete Number: ");
result.append(idString);
result.append("\nFirst Name: ");
result.append(firstName);
result.append("\nFamily Name: ");
result.append(lastName);
result.append("\nClass1\n");
for(Race race : class1Races) {
result.append(race.toString());
result.append("\n");
}
result.append("Class2\n");
for(Race race : class2Races) {
result.append(race.toString());
result.append("\n");
}
return result.toString();
}
void setId(int id) {
this.id = id;
}
void setFirstName(String firstName) {
this.firstName = firstName;
}
void setLastName(String lastName) {
this.lastName = lastName;
}
void addRaceClass1(Race race) {
class1Races.add(race);
}
void addRaceClass2(Race race) {
class2Races.add(race);
}
}
public class Race { //And accompanying Race class to hold information about a race.
private String name;
private int position;
private int points;
public Race(String name,int position,int points) {
this.name = name;
this.position = position;
this.points = points;
}
@Override
public String toString() {
String positionString = Integer.toString(position);
String pointsString = Integer.toString(points);
StringBuilder result = new StringBuilder(42 + name.length() + positionString.length() + pointsString.length());
result.append("Position and points awarded for ");
result.append(name);
result.append(" race: ");
result.append(positionString);
result.append(" ");
result.append(pointsString);
return result.toString();
}
//...probably some getters, if you need them elsewhere.
}
接下来，您将需要解析该文件。我不知道完整的文件规范，但通过你的例子，我猜：
private List<Athlete> parseAthletes(String filename) throws IOException {
List<Athlete> result = new ArrayList<>(12);
BufferedReader br = new BufferedReader(new FileReader(filename));
Athlete athlete = null;
int currentClass = 0;
String line = null; //Loop as long as there are input lines.
while((line = br.readLine()) != null) { //Sets the line variable and reads it all at once!
if(line.startsWith("Athlete Number: ")) {
athlete = new Athlete();
result.add(athlete);
athlete.setId(Integer.parseInt(line.substring(16))); //Throws NumberFormatException if not a number.
currentClass = 0;
} else if(line.startsWith("First Name: ")) {
if(athlete == null) //No Athlete Number was seen yet.
throw new IOException("Wrong format!");
athlete.setFirstName(line.substring(12));
} else if(line.startsWith("Family Name: ")) {
if(athlete == null)
throw new IOException("Wrong format!");
athlete.setLastName(line.substring(13));
} else if(line.startsWith("Class ")) {
if(athlete == null)
throw new IOException("Wrong format!");
currentClass = Integer.parseInt(line.substring(6)); //Throws NumberFormatException if not a number.
} else if(line.startsWith("Position and points awarded for ") && line.contains(" race: ")) {
if(athlete == null || (currentClass != 1 && currentClass != 2))
throw new IOException("Wrong format!"); //Need to have seen an athlete as well as a class number.
String raceName = line.substring(32,line.indexOf(" race: ",32));
line = line.substring(line.indexOf(" race: ",32) + 7); //Trim off the start.
int position = Integer.parseInt(line.substring(0,line.indexOf(" ")));
int points = Integer.parseInt(line.substring(line.indexOf(" ") + 2));
Race race = new Race(raceName,position,points);
if(currentClass == 1)
athlete.addRaceClass1(race);
else //We already know class must be 2.
athlete.addRaceClass2(race);
}
}
return result;
}
如果类号可能不仅仅是1和2，您可能需要列出比赛列表。通过缓存indexOf查询也可以提高效率。但通常性能不是真正的问题这些文件解析器;如果这是一个问题，你最好不要试图并行完成阅读并使用二进制格式。
最后，要按ID对列表进行排序，您可以使用Comparator。您甚至不需要为它创建一个全新的类，您只需匿名定义Comparator的实例：
List<Athlete> athletes = parseAthletes("athlete.txt");
Comparator<Athlete> athletesById = new Comparator<Athlete>() {
@Override
public int compare(Athlete a,Athlete b) {
return Integer.compare(a.getId(),b.getId());
}
}
Collections.sort(athletes,athletesById);
for(Athlete athlete : athletes) {
System.out.println(athlete.toString());
}
该比较器定义了比较两个Athlete，只需要比较ID。
我可能在这里或那里犯了一个错字，或者出现了逻辑错误，所以请彻底测试这段代码，或者更好的是，受它启发，然后自己编写代码。