作为我正在研究的项目的一部分，我们需要一个“Song”对象，其列表在ArrayList“songCollection”中。我需要根据标题，排名，艺术家或年份合并排序文件，但执行时，代码进入无限循环（StackOverflow Error），我不知道为什么。我的代码出了什么问题： 歌曲列表： 1965年55加里刘易斯和花花公子每个人都喜欢小丑 1963 526 Ben E. King我怎么能忘记 1979年207阿什福德和辛普森发现一个治愈1981年96安迪吉布时间是时间1996年169总计男孩遇见女孩 1962年384 Linda Scott Yesiree 1957 315 Frank Sinatra你对我的爱 1978 302约翰丹佛我想活下去 1954年304 Stan Kenton＆amp;他的乐团The Creep 1993 199Expos�尽我所能 1989 269上议院我想被爱 1950 267 Benny Goodman六重奏哦，宝贝！ 1948 295 Tex Williams＆amp; Western Caravan Suspicion
代码： //将上面一行更改为歌曲，将其添加到songCollection
ArrayList<Song> songCollection = new ArrayList<Song>();
public SongCollection(String fileName) throws FileNotFoundException {
Scanner input = new Scanner(new File(fileName));
while (input.hasNextLine())
{
addSong(input.nextLine());
}
}
//getter method
public ArrayList<Song> getSongCollection() {
return songCollection;
}
public void addSong(String line) {
//parse the line read from the song file, create the song, and add it to the collection
StringTokenizer token = new StringTokenizer(line, "\t");
String year = token.nextToken();
int intYear = Integer.parseInt(year);
String rank = token.nextToken();
int intRank = Integer.parseInt(rank);
String artist = token.nextToken();
String name = token.nextToken();
Song song = new Song(intYear, intRank, artist, name);
songCollection.add(song);
}
public ArrayList<Song> mergeSort(ArrayList<Song> all, String filter, String file) throws FileNotFoundException {
//overarching method, divides the array list into left and right array lists, then divides and sorts, and then finally merges back
//distinction: use of mergeString vs mergeInt based on the type of filter that the list is being sorted for.
ArrayList<Song> left = new ArrayList<Song>();
ArrayList<Song> right = new ArrayList<Song>();
int center;
if (all.size() == 1) {
return all;
}
else {
center = all.size()/2;
for (int i=center; i<all.size(); i++) {
right.add(all.get(i));
}
//left = mergeSort(left,filter, file);
//right = mergeSort(right, filter, file);
// Merge the results back together.
if (filter.equalsIgnoreCase("year") || filter.equalsIgnoreCase("rank"))
mergeInt(left, right, all, filter);
if (filter.equalsIgnoreCase("artist") || filter.equalsIgnoreCase("title"))
mergeString(left,right,all,filter);
}
PrintStream out = new PrintStream(new File(file));
for (int x = 0; x < songCollection.size(); x++) {
out.println(all.get(x).toString());
}
out.close();
return all;
}
private void mergeString(ArrayList<Song> left, ArrayList<Song> right, ArrayList<Song> whole, String filter) {
//'mergeX' for the string filters
int leftIndex = 0;
int rightIndex = 0;
int wholeIndex = 0;
//checks whether filter is artist or type
if(filter.equalsIgnoreCase("artist")) {
while (leftIndex < left.size() && rightIndex < right.size()) {
if ( (left.get(leftIndex).artist.compareTo(right.get(rightIndex).artist)) < 0) {
whole.set(wholeIndex, left.get(leftIndex));
leftIndex++;
} else {
whole.set(wholeIndex, right.get(rightIndex));
rightIndex++;
}
wholeIndex++;
}
ArrayList<Song> rest;
int restIndex;
if (leftIndex >= left.size()) {
// The left ArrayList has been use up...
rest = right;
restIndex = rightIndex;
} else {
rest = left;
restIndex = leftIndex;
}
for (int i=restIndex; i<rest.size(); i++) {
whole.set(wholeIndex, rest.get(i));
wholeIndex++;
}
}
if(filter.equalsIgnoreCase("title")) {
while (leftIndex < left.size() && rightIndex < right.size()) {
if ( (left.get(leftIndex).title.compareTo(right.get(rightIndex).title)) < 0) {
whole.set(wholeIndex, left.get(leftIndex));
leftIndex++;
} else {
whole.set(wholeIndex, right.get(rightIndex));
rightIndex++;
}
wholeIndex++;
}
ArrayList<Song> rest;
int restIndex;
if (leftIndex >= left.size()) {
rest = right;
restIndex = rightIndex;
} else {
rest = left;
restIndex = leftIndex;
}
for (int i=restIndex; i<rest.size(); i++) {
whole.set(wholeIndex, rest.get(i));
wholeIndex++;
}
}
}
private void mergeInt(ArrayList<Song> left, ArrayList<Song> right, ArrayList<Song> whole, String filter) {
//same as mergeString, but for int fields
int leftIndex = 0;
int rightIndex = 0;
int wholeIndex = 0;
if(filter.equalsIgnoreCase("year")) {
while (leftIndex < left.size() && rightIndex < right.size()) {
if (left.get(leftIndex).year < right.get(rightIndex).year) {
whole.set(wholeIndex, left.get(leftIndex));
leftIndex++;
} else {
whole.set(wholeIndex, right.get(rightIndex));
rightIndex++;
}
wholeIndex++;
}
ArrayList<Song> rest;
int restIndex;
if (leftIndex >= left.size()) {
rest = right;
restIndex = rightIndex;
} else {
rest = left;
restIndex = leftIndex;
}
for (int i=restIndex; i<rest.size(); i++) {
whole.set(wholeIndex, rest.get(i));
wholeIndex++;
}
}
if(filter.equalsIgnoreCase("rank")) {
while (leftIndex < left.size() && rightIndex < right.size()) {
if (left.get(leftIndex).rank < (right.get(rightIndex).rank)) {
whole.set(wholeIndex, left.get(leftIndex));
leftIndex++;
} else {
whole.set(wholeIndex, right.get(rightIndex));
rightIndex++;
}
wholeIndex++;
}
ArrayList<Song> rest;
int restIndex;
if (leftIndex >= left.size()) {
rest = right;
restIndex = rightIndex;
} else {
rest = left;
restIndex = leftIndex;
}
for (int i=restIndex; i<rest.size(); i++) {
whole.set(wholeIndex, rest.get(i));
wholeIndex++;
}