[英]How to write a class with generic comparator for sorting list?
我為HotelData
提供了以下模型,
public class HotelData {
private String name;
private String address;
private String stars;
private String contact;
private String phone;
private String uri;
public HotelData(String name, String address, String stars, String contact, String phone, String uri) {
this.name = name;
this.address = address;
this.stars = stars;
this.contact = contact;
this.phone = phone;
this.uri = uri;
}
public HotelData() {
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
public String getStars() {
return stars;
}
public void setStars(String stars) {
this.stars = stars;
}
public String getContact() {
return contact;
}
public void setContact(String contact) {
this.contact = contact;
}
public String getPhone() {
return phone;
}
public void setPhone(String phone) {
this.phone = phone;
}
public String getUri() {
return uri;
}
public void setUri(String uri) {
this.uri = uri;
}
}
我在類中使用以下方法對List<HotelData>
進行排序,即rows
。
public class Sorter {
public static void sortDataList(int sortValue, List<HotelData> rows) {
switch (sortValue) {
// sort based on the name
case 1:
Collections.sort(rows, new Comparator<HotelData>() {
@Override
public int compare(HotelData p1, HotelData p2) {
return p1.getName().compareTo(p2.getName()); // Ascending
}
});
break;
// sort based on the hotel rating
case 2:
Collections.sort(rows, new Comparator<HotelData>() {
@Override
public int compare(HotelData p1, HotelData p2) {
// return p1.getStars().compareTo(p2.getStars()); // Ascending
return p2.getStars().compareTo(p1.getStars()); // Descending
}
});
break;
default:
System.out.println("SORTING TYPE NOT SUPPORTED");
}
}
}
因此,該方法的主要作用是根據某些屬性對List<HotelData>
排序並返回結果。 如何使類和方法通用? 我還想將Java 8用於IntelliJ建議的實現
您可以使用Java的多態性(如以下步驟所示)使其通用並避免switch
情況:
(1)定義通用Sorter
類(采用任何HotelData
比較器類型)
(2)定義各種Comparator
類
代碼如下所示:
分類器類
public class Sorter {
public static void sortDataList(List<HotelData> rows,
Comparator<HotelData> comparator) {
//Sort using the provided comparator
Collections.sort(rows, comparator);
}
}
HotelNameComparator類:
public class HotelNameComparator implements Comparator<HotelData> {
@Override
public int compare(HotelData p1, HotelData p2) {
return p1.getName().compareTo(p2.getName()); // Ascending
}
}
HotelStarsComparator類:
public class HotelStarsComparator implements Comparator<HotelData> {
@Override
public int compare(HotelData p1, HotelData p2) {
return p1.getStars().compareTo(p2.getStars()); // Ascending
}
}
用法:
public static void main(String[] args) {
//First load arraylist rows
//Compares by HotelName
Sorter. sortDataList(rows, new HotelNameComparator());
//Compares by HotelStars
Sorter. sortDataList(rows, new HotelStarsComparator());
}
注意: 如果使用的是Java8,則無需編寫此冗長的代碼,而是可以非常簡單地執行以下操作:
rows.sort(Comparator.comparing(HotelData::getName));
rows.sort(Comparator.comparing(HotelData:: getStars));
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