Java 如何按属性对对象数组列表进行排序？
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How to sort an arraylist of objects by a property?
提问by sieve411
Lets say you have an Arraylistof HockeyPlayerobjects.
比方说你有一个Arraylist的HockeyPlayer对象。
How could you sort that if they all have a variable int goalsScored. How could you sort them by goalsScored?
如果它们都有一个变量int targetsScored，你怎么能排序呢？你怎么能按进球数对他们进行排序？
回答by duffymo
Write a custom Comparatorto do the job.
编写一个自定义比较器来完成这项工作。
回答by camickr
Use a generic Comparator like the Bean Comparator.
使用像Bean Comparator这样的通用Comparator。
回答by CWF
Java has a set of sort() methods for this sort of thing. See Collections.sort (and Comparable) for details.
Java 有一组 sort() 方法来处理这类事情。有关详细信息，请参阅 Collections.sort（和 Comparable）。
回答by polygenelubricants
You can use Collections.sortwith a custom Comparator<HockeyPlayer>.
您可以使用Collections.sort自定义Comparator<HockeyPlayer>.
class HockeyPlayer {
public final int goalsScored;
// ...
};
List<HockeyPlayer> players = // ...
Collections.sort(players, new Comparator<HockeyPlayer>() {
@Override public int compare(HockeyPlayer p1, HockeyPlayer p2) {
return p1.goalsScored - p2.goalsScored; // Ascending
}
});
The comparision part can also be written this way :
比较部分也可以这样写：
players.sort(Comparator.comparingInt(HockeyPLayer::goalsScored));
Alternatively, you can make HockeyPlayer implementsComparable<HockeyPlayer>. This defines thenatural ordering for all HockeyPlayerobjects. Using a Comparatoris more flexible in that different implementations can order by name, age, etc.
或者，您可以制作HockeyPlayer implementsComparable<HockeyPlayer>. 这定义了所有HockeyPlayer对象的自然顺序。使用 aComparator更灵活，因为不同的实现可以按名称、年龄等排序。
See also
也可以看看
For completeness, I should caution that the return o1.f - o2.fcomparison-by-subtraction shortcut must be used with extreme caution due to possible overflows (read: Effective Java 2nd Edition: Item 12: Consider implementing Comparable). Presumably hockey isn't a sport where a player can score goals in the amount that would cause problems =)
为了完整起见，我应该警告说，return o1.f - o2.f由于可能的溢出，必须极其谨慎地使用减法比较快捷方式（阅读：Effective Java 2nd Edition：Item 12：考虑实现Comparable）。大概曲棍球不是一项运动，其中球员可以进球的数量会导致问题=）
See also
也可以看看
回答by user6158055
Just one line with Java 8 :
与 Java 8 仅一行：
Collections.sort(players, (p1, p2) -> p1.getGoalsScored() - p2.getGoalsScored());
回答by Arpit Aggarwal
As @user6158055 suggets, it's one liner with Java 8, as follows:
正如@user6158055 所暗示的那样，它是一个带有 的衬垫Java 8，如下所示：
Collections.sort(
hockeyPlayerList,
(player1, player2) -> player1.getGoalsScored()
- player2.getGoalsScored());
Complete example to depict the same:
描述相同的完整示例：
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
public class Main {
public static void main(String[] args) {
List<HockeyPlayer> hockeyPlayerList = new ArrayList<>();
hockeyPlayerList.add(new HockeyPlayer("A", 3));
hockeyPlayerList.add(new HockeyPlayer("D", 10));
hockeyPlayerList.add(new HockeyPlayer("B", 2));
System.out.println("Before Sort based on goalsScored\n");
hockeyPlayerList.forEach(System.out::println);
System.out.println("\nAfter Sort based on goalsScored\n");
Collections.sort(
hockeyPlayerList,
(player1, player2) -> player1.getGoalsScored()
- player2.getGoalsScored());
hockeyPlayerList.forEach(System.out::println);
}
static class HockeyPlayer {
private String name;
private int goalsScored;
public HockeyPlayer(final String name, final int goalsScored) {
this.name = name;
this.goalsScored = goalsScored;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getGoalsScored() {
return goalsScored;
}
public void setGoalsScored(int goalsScored) {
this.goalsScored = goalsScored;
}
@Override
public String toString() {
return "HockeyPlayer [name=" + name + ", goalsScored="
+ goalsScored + "]";
}
}
}
Output:
输出：
Before Sort based on goalsScored
HockeyPlayer [name=A, goalsScored=3]
HockeyPlayer [name=D, goalsScored=10]
HockeyPlayer [name=B, goalsScored=2]
After Sort based on goalsScored
HockeyPlayer [name=B, goalsScored=2]
HockeyPlayer [name=A, goalsScored=3]
HockeyPlayer [name=D, goalsScored=10]
回答by Satyajit
With Java 8 this is simple
使用 Java 8 这很简单
Collections.sort(playList, Comparator.comparingInt(HockeyPLayer::goalsScored))
