java - 为什么我的输出文件是空的？

Question

当我遇到一个错误时，我正在为我的 AP 计算机科学类(class)开发一个允许用户对音乐进行排序的项目。程序解析这种格式的一行 -> year (tab) rank (tab) artist (tab) title (tab)。然后它可以按年份、排名、艺术家和/或标题对歌曲进行排序或过滤。此信息通过格式如下的输入文件加载:

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
...

我不确定如何在不泄露我的所有代码的情况下传达我的问题，所以就在这里。

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;
   }
}

为什么我输出信息时文件是空白的？

Answer 1

您永远不会关闭您的outFile。添加 outfile.close() 添加程序的结尾。