Java:将 Arraylist 打印到输出文件? [英] Java: Printing Arraylist to Output File?
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问题描述
要测试这些情况，请将排序和过滤方法更改为以下内容:
To test these cases, change sort and filter methods to the following:
示例排序方法:
public void sortTitle() {
Collections.sort(songs2, SongComparator.byTitle()); // now we have a sorted list
}
示例过滤器方法(用于字符串输入):
EXAMPLE FILTER METHOD (FOR STRING INPUT):
public void filterTitle(String s) {
int n = 0;
if (n == 0) {
n++;
for (Song song1 : songs2) {
if ((!(((song1.title).contains(s))))) {
itemsToRemove.add(song1);
}
}
songs2.removeAll(itemsToRemove);
itemsToRemove.clear();
}
}
示例过滤器方法(用于 INT 输入):
EXAMPLE FILTER METHOD (FOR INT INPUT):
public void filterRank(Range r) {
int n = 0;
if (n == 0) {
n++;
for (Song song1 : songs2) {
if (song1.rank > (r.getMax()) || (song1.rank) < (r.getMin())) {
itemsToRemove.add(song1);
}
}
songs2.removeAll(itemsToRemove);
itemsToRemove.clear();
}
}
测试案例:
输入字符串应该像下面的例子:
Input strings should be like the following examples:
sort:title
此输入成功运行，直到主类中的 System.setOut(out); 行，它开始打印空格并且没有成功打印集合.这可能是因为 SongCollection 类中的 toString 方法有问题.
This input runs successfully until
the line System.setOut(out); in the main class, where it begins to print spaces and does not successfully print the collection. This may be because of a problem with the toString method in the SongCollection class.
artist:Paramore
或
title:Misery Business
这个输入在整个程序中成功运行(程序没有终止，因为 while 循环没有终止)，除了打印一个空格而不是打印集合.
This input runs successfully through the entire program (the program does not terminate because the while loop does not terminate), except instead of printing the collection, a blank space is printed.
其他细节:
这个问题是我之前提出的问题的后续问题，因为我对这个项目的时间限制很短(明天到期).我遇到的主要问题是程序无法正确输出，即使主要用于打印的方法和代码在逻辑上是合理的.
This question is a followup to a previous question I asked, since I have short time constraints on this project (it is due tomorrow). The primary problem I am experiencing with this is that the program is failing to output correctly, even though the methods and code in the main for printing seems logically sound.
出于某种原因，将 ArrayLists 打印到输出文件需要花费大量时间，通常为 20-30 分钟.然而，这只发生在 sort 方法或 filterTitle 或 filterArtist 方法(涉及字符串输入的方法).当我运行 filterRank 或 filterYear 时，它运行得非常好.
For some reason, it takes an extraordinary amount of time for the ArrayLists to be printed to the output file, usually 20-30 minutes. However, this only happens with the sort methods or the filterTitle or filterArtist methods (methods that concern String inputs).
When I run filterRank or filterYear, it runs perfectly fine.
当我直接从过滤器方法打印song2 ArrayList时，唯一打印的是[]，这意味着ArrayList是空的，但它不应该是?无论如何，filterRank 和 filterYear 方法仍然有效.不过，我认为这是相关的.
When I print the song2 ArrayList directly from the filter methods, the only thing that is printed is [], which means the ArrayList is empty, but it shouldn't be? And the filterRank and filterYear methods still work regardless of this.
Somehow I think it's related, though.
输入文件可以在这里找到:http://staff.rentonschools.us/hhs/ap-comp-science/projects/download/agazillionsongs.txt?id=223098
Input file can be found here: http://staff.rentonschools.us/hhs/ap-comp-science/projects/download/agazillionsongs.txt?id=223098
完整的编译代码:
import java.io.*;
import java.io.File;
import java.io.FileNotFoundException;
import java.util.*;
import java.util.Comparator;
import java.util.Scanner;
import java.util.StringTokenizer;
public class GazillionSongs {
public static void main(String[] args) throws FileNotFoundException, IOException {
System.out.println("Welcome to Java Song Collection!"); // greets the user
System.out
.println("This program sorts and filters large databases of popular songs."); // explains purpose of program
System.out
.println("This program is able to filter and sort by year, artist, title and rank.");
System.out
.println("Please enter a file that contains a database you wish to filter or sort. (i.e, alistofsongs.txt)"); // sample file = agazillionsongs.txt
Scanner fileInput = new Scanner(System.in); //Scanner which accepts filename
String filename = fileInput.nextLine();
File f = new File(filename); //creates file from input
/*error check for file here*/
Scanner fileScanner = new Scanner(f); //inputs data from file
ArrayList<Song> songs = new ArrayList<Song>();
while ((fileScanner.hasNextLine())) {
songs.add(Song.parse(fileScanner.nextLine()));
}
System.out
.println("Please select which commands you would like to use for the program.");
System.out
.println("Please format your command like the following example: year:<year(s)> rank:<rank(s)> artist:<artist> title:<title> sortBy:<field>");
System.out.println();
System.out.println("You may pick any number of commands you want.");
System.out
.println("For years and rank, you may select a range of years or ranks.");
System.out
.println("For artists and titles, you may enter a partial name or title.");
System.out.println("i.e, year:1983 rank:1");
Scanner input = new Scanner(System.in);
while (input.hasNextLine()) {
int n = 0;
SongCollection collection = new SongCollection(songs);
String inputType = input.nextLine();
String delims = "[ ]";
String[] tokens = inputType.split(delims);
for (int i = 0; i < tokens.length; i++) {
n = 0;
if (n == 0) {
if ((tokens[i]).contains("year:")) {
collection.filterYear(Range.parse(tokens[i]));
n = 1;
}// end of year loop
if ((tokens[i]).contains("rank:")) {
collection.filterRank(Range.parse(tokens[i]));
n = 1;
}// end of rank
if ((tokens[i]).contains("artist:")) {
collection.filterArtist(tokens[i]);
n = 1;
}// end of artist
if ((tokens[i]).contains("title:")) {
collection.filterTitle(tokens[i]);
n = 1;
}// end of title
if ((tokens[i]).contains("sort:")) {
if ((tokens[i]).contains("title")) {
collection.sortTitle();
n = 1;
}// end of sort title
if ((tokens[i]).contains("artist")) {
collection.sortArtist();
n = 1;
}// end of sort artist
if ((tokens[i]).contains("rank")) {
collection.sortRank();
n = 1;
}// end of sort rank
if ((tokens[i]).contains("year")) {
collection.sortYear();
n = 1;
}// end of sort year
}//end of sort
}// end of for loop
}// end of input.hasNextline loop
final PrintStream console = System.out; //saves original System.out
File outputFile = new File("output.txt"); //output file
PrintStream out = new PrintStream(new FileOutputStream(outputFile)); //new FileOutputStream
System.setOut(out); //changes where data will be printed
System.out.println(collection.toString());
System.setOut(console); //changes output to print back to console
Scanner outputFileScanner = new Scanner(outputFile); //inputs data from file
while ((outputFileScanner.hasNextLine())) { //while the file still has data
System.out.println(outputFileScanner.nextLine()); //print
}
outputFileScanner.close();
out.close();
}
}// end of main
}// end of class
class Song{
public enum Order {Year, Rank, Title, Artist}
public int year;
public int rank;
public String artist;
public String title;
public static Song parse(String s) {
Song instance = new Song();
StringTokenizer tokenizer = new StringTokenizer(s, "\t");
instance.year = Integer.parseInt(tokenizer.nextToken());
instance.rank = Integer.parseInt(tokenizer.nextToken());
instance.artist = (tokenizer.nextToken());
instance.title = (tokenizer.nextToken());
return instance;
}
public int getYear() {
return year;
}
public int getRank() {
return rank;
}
public String getArtist() {
return artist;
}
public String getTitle() {
return title;
}
public String toString() {
String output = "\n\nYear = " + year + "\nRank = " + rank + "\nArtist = "
+ artist + "\nTitle = " + title;
return output;
}
}
class Range {
private int min;
private int max;
public Range() {
System.out.println("Please wait.");
}
public static Range parse(String s) {
Range instance = new Range(); // instance is created here so object
// variables may be accessed
String field; // String to contain deleted part of user input
StringTokenizer tokenizer = new StringTokenizer(s, "-");
StringTokenizer tokenizer2 = new StringTokenizer(s, ":");// for separating "field:" from the
// other part of the String
if (s.contains(":")) { // this deletes the "field:" of the user input so
// it does not interfere with the parsing
field = (tokenizer2.nextToken());
s = s.replace(field, "");
s = s.replace(":", "");
}
if (s.contains("-")) {
instance.min = Integer.parseInt(tokenizer.nextToken());
instance.max = Integer.parseInt(tokenizer.nextToken());
} else if (!(s.contains("-"))) {
{
instance.min = Integer.parseInt(s);
instance.max = Integer.parseInt(s);
}
}
System.out.println("Range max = " + instance.max);
System.out.println("Range min = " + instance.min);
return instance;
}
public boolean contains(int n) {
if (n > min && n < max) { //if the number is contained in the range, method returns true.
return true;
} else if (n == min && n == max) {
return true;
} else {
return false;
}
}
public int getMin() {
return min;
}
public int getMax() {
return max;
}
}
class SongCollection {
ArrayList<Song> songs2;
ArrayList<Song> itemsToRemove = new ArrayList<Song>(); // second collection
// for items to
// remove
public SongCollection(ArrayList<Song> songs) { // constructor for SongCollection
System.out.println("Test");
this.songs2 = songs;
}
public void filterYear(Range r) {
int n = 0;
if (n == 0) {
System.out.println("Program is processing.");
n++;
for (Song song1 : songs2) {
if (song1.year > (r.getMax()) || (song1.year) < (r.getMin())) {
itemsToRemove.add(song1);
}
}
songs2.removeAll(itemsToRemove);
itemsToRemove.clear();
}
System.out.println(songs2);
}
public void filterRank(Range r) {
int n = 0;
if (n == 0) {
System.out.println("Program is processing.");
n++;
for (Song song1 : songs2) {
if (song1.rank > (r.getMax()) || (song1.rank) < (r.getMin())) {
itemsToRemove.add(song1);
}
}
songs2.removeAll(itemsToRemove);
itemsToRemove.clear();
}
System.out.println(songs2);
}
public void filterArtist(String s) {
int n = 0;
if (n == 0) {
System.out.println("Program is processing.");
n++;
for (Song song1 : songs2) {
if ((!(((song1.artist).contains(s))))) {
itemsToRemove.add(song1);
}
}
songs2.removeAll(itemsToRemove);
itemsToRemove.clear();
}
System.out.println(songs2);
}
public void filterTitle(String s) {
int n = 0;
if (n == 0) {
System.out.println("Program is processing.");
n++;
for (Song song1 : songs2) {
if ((!(((song1.title).contains(s))))) {
itemsToRemove.add(song1);
}
}
songs2.removeAll(itemsToRemove);
itemsToRemove.clear();
}
System.out.println(songs2);
}
public void sortTitle() {
Collections.sort(songs2, SongComparator.byTitle()); // now we have a sorted list
System.out.println(songs2);
}
public void sortRank() {
Collections.sort(songs2, SongComparator.byRank()); // now we have a sorted list
System.out.println(songs2);
}
public void sortArtist() {
Collections.sort(songs2, SongComparator.byArtist()); // now we have a sorted list
System.out.println(songs2);
}
public void sortYear() {
Collections.sort(songs2, SongComparator.byYear()); // now we have a sorted list
System.out.println(songs2);
}
public String toString() {
String result = "";
for (int i = 0; i < songs2.size(); i++) {
result += " " + songs2.get(i);
}
return result;
}
}
class SongComparator implements Comparator<Song> {
public enum Order{
YEAR_SORT, RANK_SORT, ARTIST_SORT, TITLE_SORT
}
private Order sortingBy;
public SongComparator(Order sortingBy){
this.sortingBy = sortingBy;
}
public static SongComparator byTitle() {
return new SongComparator(SongComparator.Order.TITLE_SORT);
}
public static SongComparator byYear() {
return new SongComparator(SongComparator.Order.YEAR_SORT);
}
public static SongComparator byArtist() {
return new SongComparator(SongComparator.Order.ARTIST_SORT);
}
public static SongComparator byRank() {
return new SongComparator(SongComparator.Order.RANK_SORT);
}
@Override
public int compare(Song song1, Song song2) {
switch (sortingBy) {
case YEAR_SORT:
return Integer.compare(song1.year, song2.year);
case RANK_SORT:
return Integer.compare(song1.rank, song2.rank);
case ARTIST_SORT:
return song1.artist.compareTo(song2.artist);
case TITLE_SORT:
return song1.title.compareTo(song2.title);
}
throw new RuntimeException(
"Practically unreachable code, can't be thrown");
}
}
推荐答案
我尝试运行此代码，它运行良好且速度很快.我正在使用您发布的文件，如您所见，搜索的测试值为year:1983 sort:title".我还通过删除 while 循环和用户输入的文件名和过滤器字符串来简化它，因此任何人都可以轻松重现它.
I tried to run this code and it works fine and fast. I am using file you posted and as you can see, test value for searching is "year:1983 sort:title". I also simplified it by removing while-cycle and user-input filename and filter string, so anyone can easily reproduce it.
如果您想提供帮助，我需要知道如何将 20-30 分钟的输出复制到文件中.:
If you want to help, I need to know, how to reproduce that 20-30 minute outputing to file. :
import java.io.*;
import java.io.File;
import java.io.FileNotFoundException;
import java.util.*;
import java.util.Comparator;
import java.util.Scanner;
import java.util.StringTokenizer;
public class GazillionSongs {
public static void main(String[] args) throws FileNotFoundException, IOException {
Scanner input = new Scanner(System.in);
System.out.println("Welcome to Java Song Collection!"); // greets the user
System.out
.println("This program sorts and filters large databases of popular songs."); // explains purpose of program
System.out
.println("This program is able to filter and sort by year, artist, title and rank.");
System.out
.println("Please enter a file that contains a database you wish to filter or sort. (i.e, alistofsongs.txt)"); // sample file = agazillionsongs.txt
File f = new File("agazillionsongs.txt"); //creates file from input
/*error check for file here*/
Scanner fileScanner = new Scanner(f); //inputs data from file
List<Song> songs = new ArrayList<Song>();
while ((fileScanner.hasNextLine())) {
Song song = Song.parse(fileScanner.nextLine());
songs.add(song);
}
System.out
.println("Please select which commands you would like to use for the program.");
System.out
.println("Please format your command like the following example: year:<year(s)> rank:<rank(s)> artist:<artist> title:<title> sortBy:<field>");
System.out.println();
System.out.println("You may pick any number of commands you want.");
System.out
.println("For years and rank, you may select a range of years or ranks.");
System.out
.println("For artists and titles, you may enter a partial name or title.");
System.out.println("i.e, year:1983 rank:1");
int n = 0;
SongCollection collection = new SongCollection(songs);
String inputType = "year:1983 sort:title";
String delims = "[ ]";
String[] tokens = inputType.split(delims);
for (int i = 0; i < tokens.length; i++) {
n = 0;
if (n == 0) {
if ((tokens[i]).contains("year:")) {
collection.filterYear(Range.parse(tokens[i]));
n = 1;
}// end of year loop
if ((tokens[i]).contains("rank:")) {
collection.filterRank(Range.parse(tokens[i]));
n = 1;
}// end of rank
if ((tokens[i]).contains("artist:")) {
collection.filterArtist(tokens[i]);
n = 1;
}// end of artist
if ((tokens[i]).contains("title:")) {
collection.filterTitle(tokens[i]);
n = 1;
}// end of title
if ((tokens[i]).contains("sort:")) {
if ((tokens[i]).contains("title")) {
collection.sortTitle();
n = 1;
}// end of sort title
if ((tokens[i]).contains("artist")) {
collection.sortArtist();
n = 1;
}// end of sort artist
if ((tokens[i]).contains("rank")) {
collection.sortRank();
n = 1;
}// end of sort rank
if ((tokens[i]).contains("year")) {
collection.sortYear();
n = 1;
}// end of sort year
}//end of sort
}// end of for loop
}// end of input.hasNextline loop
final PrintStream console = System.out; //saves original System.out
File outputFile = new File("output.txt"); //output file
PrintStream out = new PrintStream(new FileOutputStream(outputFile)); //new FileOutputStream
System.setOut(out); //changes where data will be printed
System.out.println(collection.toString());
System.setOut(console); //changes output to print back to console
Scanner outputFileScanner = new Scanner(outputFile); //inputs data from file
while ((outputFileScanner.hasNextLine())) { //while the file still has data
System.out.println(outputFileScanner.nextLine()); //print
}
outputFileScanner.close();
out.close();
}
}// end of main
class Song {
public enum Order {
Year, Rank, Title, Artist
}
public int year;
public int rank;
public String artist;
public String title;
public static Song parse(String s) {
Song instance = new Song();
StringTokenizer tokenizer = new StringTokenizer(s, "\t");
instance.year = Integer.parseInt(tokenizer.nextToken());
instance.rank = Integer.parseInt(tokenizer.nextToken());
instance.artist = (tokenizer.nextToken());
instance.title = (tokenizer.nextToken());
return instance;
}
public int getYear() {
return year;
}
public int getRank() {
return rank;
}
public String getArtist() {
return artist;
}
public String getTitle() {
return title;
}
public String toString() {
String output = "\n\nYear = " + year + "\nRank = " + rank + "\nArtist = "
+ artist + "\nTitle = " + title;
return output;
}
}
class Range {
private int min;
private int max;
public Range() {
System.out.println("Please wait.");
}
public static Range parse(String s) {
Range instance = new Range(); // instance is created here so object
// variables may be accessed
String field; // String to contain deleted part of user input
StringTokenizer tokenizer = new StringTokenizer(s, "-");
StringTokenizer tokenizer2 = new StringTokenizer(s, ":");// for separating "field:" from the
// other part of the String
if (s.contains(":")) { // this deletes the "field:" of the user input so
// it does not interfere with the parsing
field = (tokenizer2.nextToken());
s = s.replace(field, "");
s = s.replace(":", "");
}
if (s.contains("-")) {
instance.min = Integer.parseInt(tokenizer.nextToken());
instance.max = Integer.parseInt(tokenizer.nextToken());
} else if (!(s.contains("-"))) {
{
instance.min = Integer.parseInt(s);
instance.max = Integer.parseInt(s);
}
}
System.out.println("Range max = " + instance.max);
System.out.println("Range min = " + instance.min);
return instance;
}
public boolean contains(int n) {
if (n > min && n < max) { //if the number is contained in the range, method returns true.
return true;
} else if (n == min && n == max) {
return true;
} else {
return false;
}
}
public int getMin() {
return min;
}
public int getMax() {
return max;
}
}
class SongCollection {
List<Song> songs2;
List<Song> itemsToRemove = new ArrayList<Song>(); // second collection
// for items to
// remove
public SongCollection(List<Song> songs) { // constructor for SongCollection
System.out.println("Test");
this.songs2 = songs;
}
public void filterYear(Range r) {
int n = 0;
if (n == 0) {
System.out.println("Program is processing.");
n++;
for (Song song1 : songs2) {
if (song1.year > (r.getMax()) || (song1.year) < (r.getMin())) {
itemsToRemove.add(song1);
}
}
songs2.removeAll(itemsToRemove);
itemsToRemove.clear();
}
System.out.println(songs2);
}
public void filterRank(Range r) {
int n = 0;
if (n == 0) {
System.out.println("Program is processing.");
n++;
for (Song song1 : songs2) {
if (song1.rank > (r.getMax()) || (song1.rank) < (r.getMin())) {
itemsToRemove.add(song1);
}
}
songs2.removeAll(itemsToRemove);
itemsToRemove.clear();
}
System.out.println(songs2);
}
public void filterArtist(String s) {
int n = 0;
if (n == 0) {
System.out.println("Program is processing.");
n++;
for (Song song1 : songs2) {
if ((!(((song1.artist).contains(s))))) {
itemsToRemove.add(song1);
}
}
songs2.removeAll(itemsToRemove);
itemsToRemove.clear();
}
System.out.println(songs2);
}
public void filterTitle(String s) {
int n = 0;
if (n == 0) {
System.out.println("Program is processing.");
n++;
for (Song song1 : songs2) {
if ((!(((song1.title).contains(s))))) {
itemsToRemove.add(song1);
}
}
songs2.removeAll(itemsToRemove);
itemsToRemove.clear();
}
System.out.println(songs2);
}
public void sortTitle() {
Collections.sort(songs2, SongComparator.byTitle()); // now we have a sorted list
System.out.println(songs2);
}
public void sortRank() {
Collections.sort(songs2, SongComparator.byRank()); // now we have a sorted list
System.out.println(songs2);
}
public void sortArtist() {
Collections.sort(songs2, SongComparator.byArtist()); // now we have a sorted list
System.out.println(songs2);
}
public void sortYear() {
Collections.sort(songs2, SongComparator.byYear()); // now we have a sorted list
System.out.println(songs2);
}
public String toString() {
String result = "";
for (int i = 0; i < songs2.size(); i++) {
result += " " + songs2.get(i);
}
return result;
}
}
class SongComparator implements Comparator<Song> {
public enum Order {
YEAR_SORT, RANK_SORT, ARTIST_SORT, TITLE_SORT
}
private Order sortingBy;
public SongComparator(Order sortingBy) {
this.sortingBy = sortingBy;
}
public static SongComparator byTitle() {
return new SongComparator(SongComparator.Order.TITLE_SORT);
}
public static SongComparator byYear() {
return new SongComparator(SongComparator.Order.YEAR_SORT);
}
public static SongComparator byArtist() {
return new SongComparator(SongComparator.Order.ARTIST_SORT);
}
public static SongComparator byRank() {
return new SongComparator(SongComparator.Order.RANK_SORT);
}
@Override
public int compare(Song song1, Song song2) {
switch (sortingBy) {
case YEAR_SORT:
return Integer.compare(song1.year, song2.year);
case RANK_SORT:
return Integer.compare(song1.rank, song2.rank);
case ARTIST_SORT:
return song1.artist.compareTo(song2.artist);
case TITLE_SORT:
return song1.title.compareTo(song2.title);
}
throw new RuntimeException(
"Practically unreachable code, can't be thrown");
}
}
问题:
title:Misery Business
这个输入在整个程序中成功运行(程序没有终止，因为 while 循环没有终止)，除了打印一个空格而不是打印集合.
This input runs successfully through the entire program (the program does not terminate because the while loop does not terminate), except instead of printing the collection, a blank space is printed.
是的，因为在您的方法中，您正在测试是否包含 title:Misery Business 而不是 Misery Business.
Yes, because in your method, you are testing, if it contains title:Misery Business not Misery Business.
首先，您不能将该分词器用于任何包含空格的内容.但对于一个字，你可以改变它如下:
First of all, you cant use that tokenizer for anything, that contains space. But for one-word only, you can change it as following :
经过测试并为 title:Misery 工作:
Tested and working for title:Misery :
public void filterTitle(String s) {
int n = 0;
s = s.split(":")[1];
if (n == 0) {
System.out.println("Program is processing.");
n++;
for (Song song1 : songs2) {
if (song1.title.contains(s) == false) {
itemsToRemove.add(song1);
}
}
songs2.removeAll(itemsToRemove);
itemsToRemove.clear();
}
System.out.println(songs2);
}
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