[英]Java sort a list with revelance comparator
我正在嘗試根據與條件列表相對應的啟示對音樂列表進行排序。
public class Music implements Comparable<CriteriaList> {
private String genre, artist, album, titre, price, note;
// getters, setters
public int compareTo(CriteriaList list) {
boolean title, album, genre, artist, note;
title = !list.getTitle().isEmpty() && this.getTitre().equals(list.getTitle());
album = !list.getAlbum().isEmpty() && this.getAlbum().equals(list.getAlbum());
genre = !list.getGenre().isEmpty() && this.getGenre().equals(list.getGenre());
artist = !list.getArtist().isEmpty() && this.getArtist().equals(list.getArtist());
note = !list.getNote().isEmpty() && (Integer.parseInt(this.getNote()) >= Integer.parseInt(list.getNote()));
return ((title ? 1 : 0) + (album ? 1 : 0) + (genre ? 1 : 0) + (artist ? 1 : 0) + (note ? 1 : 0));
}
}
我的函數compareTo返回與條件列表匹配的字段數,並測試輸入是否為空。
public class MusicProvider extends Agent {
public List<Music> getMusicsByCL(CriteriaList list) {
ArrayList<Music> res = new ArrayList<Music>();
int[] revelanceTab = new int[res.size()];
int i = 0, revelance;
for (Music music : musicListAvailable) {
revelance = music.compareTo(list);
if (revelance > 1) {
res.add(music);
revelanceTab[++i] = revelance;
}
}
// sort res with revelanceTab
return res;
}
}
在這里,我要檢索最小啟示度為1的音樂,並按啟示性對它們進行排序。 我怎樣才能做到這一點 ?
假設您已經創建了實際計算相關性的功能,我將像這樣繼續進行。
創建一個簡單的類來保存音樂和計算出的相關性分數,只需傳遞條件並存儲計算結果即可。
public class ScoredMusic {
private int relevanceScore;
public ScoredMusic(Music m) { ... }
public void calculateRelevance(Criteria criteria) { ... }
public Music getMusic() { ... }
public int getRelevanceScore() { ... }
}
然后,我將比分你的所有音樂的情況下,將它們存儲在一個列表中,並做了非常簡單compareTo()
實現了簡單的比較relevanceScore
每間ScoredMusic
實例。
Comparable用於比較Music的兩個實例。 如果要與外部實體進行比較,請使用Comparator實現並將其傳遞給Collections.sort(List,Comparator) 。 比較器將需要使用CriteriaList進行初始化,如果第一個元素的排名較高,則compare方法將返回正數;如果第二個元素的排名較高,則compare方法將返回負數;如果等效,則返回0。 在您的示例中,您將使用compareTo方法並從第一個元素中減去第二個元素的分數,然后將其返回。
像這樣:
import java.util.Comparator;
public class MusicComparator implements Comparator<Music> {
private final CriteriaList criteria;
public MusicComparator(CriteriaList criteria) {
this.criteria = criteria;
}
@Override
public int compare(Music o1, Music o2) {
return score(o1) - score(o2);
}
private int score(Music music) {
boolean title, album, genre, artist, note;
title = criteria.getTitle().isEmpty() || criteria.getTitle().equals(music.getTitle());
album = criteria.getAlbum().isEmpty() || criteria.getAlbum().equals(music.getAlbum());
genre = criteria.getGenre().isEmpty() || criteria.getGenre().equals(music.getGenre());
artist = criteria.getArtist().isEmpty() || criteria.getArtist().equals(music.getArtist());
note = criteria.getNote().isEmpty() || (!music.getNote().isEmpty() && Integer.parseInt(music.getNote()) >= Integer.parseInt(criteria.getNote()));
return ((title ? 1 : 0) + (album ? 1 : 0) + (genre ? 1 : 0) + (artist ? 1 : 0) + (note ? 1 : 0));
}
}
順便說一句,isEmpty()方法不會保護您免受空指針異常的影響。 如果允許字段為空,則將需要一種更好的方法來處理這些字段。
這是我的最后一堂課
public class ScoredMusic implements Comparable<ScoredMusic> {
private int revelanceScore = 0;
private Music music;
public ScoredMusic(Music music, CriteriaList crit) {
this.music = music;
calculateRevelance(crit);
}
private void calculateRevelance(CriteriaList list) {
boolean title, album, genre, artist, note;
title = !list.getTitle().isEmpty() && music.getTitre().equals(list.getTitle());
album = !list.getAlbum().isEmpty() && music.getAlbum().equals(list.getAlbum());
genre = !list.getGenre().isEmpty() && music.getGenre().equals(list.getGenre());
artist = !list.getArtist().isEmpty() && music.getArtist().equals(list.getArtist());
note = !list.getNote().isEmpty() && (Integer.parseInt(music.getNote()) >= Integer.parseInt(list.getNote()));
revelanceScore = ((title ? 1 : 0) + (album ? 1 : 0) + (genre ? 1 : 0) + (artist ? 1 : 0) + (note ? 1 : 0));
}
public Music getMusic() {
return music;
}
public int getRevelanceScore() {
return revelanceScore;
}
public int compareTo(ScoredMusic other) {
return Integer.compare(this.getRevelanceScore(), other.getRevelanceScore());
}
}
在我的第二堂課
public List<ScoredMusic> getMusicsScoredByCL(CriteriaList list) {
ArrayList<ScoredMusic> scoredMusics = new ArrayList<ScoredMusic>();
ScoredMusic sc;
for (Music music : musicListAvailable) {
sc = new ScoredMusic(music, list);
scoredMusics.add(sc);
}
// sort by revelance and descending order
Collections.sort(scoredMusics, Collections.reverseOrder());
return scoredMusics;
}
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