当我遇到一个错误时，我正在为我的AP计算机科学课程开发一个允许用户对音乐进行排序的项目。该程序以这种格式解析一行 - ＆gt; year (tab) rank (tab) artist (tab) title (tab)。然后它可以按年份，等级，艺术家和/或标题对歌曲进行排序或过滤。此信息通过格式为：
2008 50 Ashley Tisdale He Said, She Said
2008 123 Taylor Swift Teardrops On My Guitar
2008 233 Finger Eleven Paralyzer
2008 258 Paramore Misery Business
...
我不确定如何在不透露我的所有代码的情况下传达我的问题，所以就是这样。
import java.util.*;
import java.io.*;
import java.util.Arrays;
public class GazillionSongs {
public static void main(String[] args) throws FileNotFoundException {
System.out.println("Hello and welcome to my AP Computer Science Music Sorting Project!");
Scanner kb = new Scanner(System.in);
System.out.print("Enter the input file: ");
String in = kb.nextLine();
Scanner inFile = new Scanner(new File(in));
System.out.print("Enter sort/filter command: ");
String command = kb.nextLine();
System.out.print("Enter an output file: ");
String out = kb.nextLine();
File f = new File(out);
if (f.exists()) {
System.out.println("Error: output file already exists...");
} else {
PrintStream outFile = new PrintStream(new File(out));
ArrayList<String> lines = new ArrayList<String>();
while (inFile.hasNextLine()) {
String line = inFile.nextLine();
lines.add(line);
}
ArrayList<Song> songs = new ArrayList<Song>();
Scanner allCommands = new Scanner(command);
for(int i = 0; i < lines.size(); i++) {
int year = 0;
int rank = 0;
String artist = "";
String title = "";
Song song = new Song(year, rank, artist, title);
song.parse(lines.get(i));
songs.add(song);
}
SongCollection songCollection = new SongCollection(songs);
while (allCommands.hasNext()) {
for(int i = 0; i < songs.size(); i++) {
String command2 = allCommands.next();
String[] tokens = command2.split(":");
if (tokens[0].equals("year")) {
int min = 0;
int max = 0;
Range range = new Range(min, max);
range.parse(tokens[1]);
songCollection.filterYear(range);
}
if (tokens[0].equals("rank")) {
int min = 0;
int max = 0;
Range range = new Range(min, max);
range.parse(tokens[1]);
songCollection.filterRank(range);
}
if (tokens[0].equals("artist")) {
songCollection.filterArtist(tokens[1]);
}
if (tokens[0].equals("title")) {
songCollection.filterTitle(tokens[1]);
}
}
}
outFile.print(songCollection.toString());
}
}
}
和
import java.io.*;
import java.util.*;
public class Song {
private static int year;
private static int rank;
private static String artist;
private static String title;
public Song(int year, int rank, String artist, String title) {
this.year = year;
this.rank = rank;
this.artist = artist;
this.title = title;
}
public static Song parse(String s) {
String[] tokens = s.split("\t");
year = Integer.parseInt(tokens[0]);
rank = Integer.parseInt(tokens[1]);
artist = tokens[2];
title = tokens[3];
Song song = new Song(year, rank, artist, title);
return song;
}
public int getYear() {
return this.year;
}
public int getRank() {
return this.rank;
}
public String getArtist() {
return this.artist;
}
public String getTitle() {
return this.title;
}
public String toString() {
String convertString = year + "/t" + rank + "/t" + artist + "/t" + title;
return convertString;
}
}
和
import java.util.*;
public class Range {
private int min;
private int max;
public int getMin() {
return min;
}
public int getMax() {
return max;
}
public Range(int min, int max) {
this.min = min;
this.max = max;
}
public static Range parse(String s) {
String[] range = s.split("-");
int min = Integer.parseInt(range[0]);
int max = 1;
try {
max = Integer.parseInt(range[1]);
} catch(ArrayIndexOutOfBoundsException err10) {
max = Integer.parseInt(range[0]);
}
if(min > max){
return new Range(max,min);
} else {
return new Range(min,max);
}
}
public boolean contains(int n) {
if(n <= max && n >= min) {
return true;
} else {
return false;
}
}
}
和
import java.util.*;
public class SongCollection {
private ArrayList<Song> songs = new ArrayList<Song>();
public SongCollection(ArrayList<Song> songs) {
this.songs = songs;
}
public ArrayList<Song> getList() {
return songs;
}
public void filterYear(Range r) {
for(int i = 0; i < songs.size(); i++) {
if(!r.contains(songs.get(i).getYear())) {
songs.remove(i);
i--;
}
}
}
public void filterRank(Range r) {
for(int i = 0; i < songs.size(); i++) {
if(!r.contains(songs.get(i).getRank())) {
songs.remove(i);
i--;
}
}
}
public void filterArtist(String s) {
for(int i = 0; i < songs.size(); i++) {
if(!songs.get(i).getArtist().toLowerCase().contains(s.toLowerCase())) {
songs.remove(i);
i--;
}
}
}
public void filterTitle(String s) {
for(int i = 0; i < songs.size(); i++) {
if(!songs.get(i).getTitle().toLowerCase().contains(s.toLowerCase())) {
songs.remove(i);
i--;
}
}
}
public void sortYear() {
for(int i = 1; i <= songs.size(); i++) {
Song temp = songs.get(i);
int j;
for (j = i - 1; j >= 0 && temp.getYear() < songs.get(j).getYear(); j--) {
songs.set((j + 1), songs.get(j));
songs.set((j), temp);
}
}
}
public void sortRank() {
for(int i = 1; i <= songs.size(); i++) {
Song temp = songs.get(i);
int j;
for (j = i - 1; j >= 0 && temp.getRank() < songs.get(j).getRank(); j--) {
songs.set((j + 1), songs.get(j));
songs.set((j), temp);
}
}
}
public void sortTitle() {
for(int i = 1; i <= songs.size(); i++) {
Song temp = songs.get(i);
int j;
for (j = i - 1; j >= 0 && temp.getTitle().toLowerCase().compareTo(songs.get(j).getTitle().toLowerCase()) < 0; j--) {
songs.set((j + 1), songs.get(j));
songs.set((j), temp);
}
}
}
public void sortArtist() {
for(int i = 1; i <= songs.size(); i++) {
Song temp = songs.get(i);
int j;
for (j = i - 1; j >= 0 && temp.getArtist().toLowerCase().compareTo(songs.get(j).getArtist().toLowerCase()) < 0; j--) {
songs.set((j + 1), songs.get(j));
songs.set((j), temp);
}
}
}
public String toString() {
String stringOfSong = "";
for(int i = 0; i < songs.size(); i++) {
stringOfSong += songs.get(i).toString() + "\n";
}
return stringOfSong;
}
}
输出信息时，为什么文件空白？
答案 0 :(得分：2)
您永远不会关闭outFile。添加outfile.close()添加程序结束。