编辑：要测试这些情况，请将排序和过滤方法更改为以下内容：
示例排序方法：
public void sortTitle() {
Collections.sort(songs2, SongComparator.byTitle()); // now we have a sorted list
}
示例过滤方法（用于输入输入）：
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();
}
}
示例过滤方法（用于INT输入）：
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：
输入字符串应类似于以下示例：
sort:title
此输入成功运行，直到
主类中的行System.setOut(out);，它开始打印空格并且不能成功打印集合。这可能是因为SongCollection类中的toString方法存在问题。
artist:Paramore
或
title:Misery Business
此输入在整个程序中成功运行（程序不会因为while循环没有终止而终止），除了打印集合外，还会打印一个空格。
其他细节：
这个问题是我问过的上一个问题的后续问题，因为我对这个项目有很短的时间限制（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看起来逻辑上合理。
Printing arraylist into output file?
出于某种原因，ArrayLists需要花费大量时间才能打印到输出文件，通常需要20-30分钟。但是，这仅适用于排序方法或filterTitle或filterArtist方法（涉及字符串输入的方法）。
当我运行filterRank或filterYear时，它运行得很好。
当我直接从过滤方法打印song2 ArrayList时，打印的唯一内容是[]，这意味着ArrayList为空，但它不应该是？无论如何，filterRank和filterYear方法仍然有效。
但不知怎的，我认为它与此有关。
输入文件可在此处找到：http://staff.rentonschools.us/hhs/ap-comp-science/projects/download/agazillionsongs.txt?id=223098
编译的完整代码：
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");
}
}
答案 0 :(得分：0)
我尝试运行此代码，但工作正常且速度很快。我正在使用您发布的文件，正如您所看到的，搜索的测试值是“年份：1983年排序：标题”。我还通过删除while-cycle和用户输入的文件名和过滤字符串来简化它，这样任何人都可以轻松地重现它。
如果你想提供帮助，我需要知道，如何重现20-30分钟输出到文件。 ：
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");
}
}
编辑：
问题：
title:Misery Business
此输入在整个程序中成功运行（程序不会因为while循环没有终止而终止），除了打印集合外，还会打印一个空格。
是的，因为在您的方法中，您正在测试，如果它包含title:Misery Business而不是Misery Business。
首先，你不能将该标记化器用于包含空间的任何东西。但仅限于单字，您可以将其更改为：
为title:Misery测试并工作：
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);
}