假设你有一个由
HockeyPlayer
对象组成的 Arraylist
。如果它们都有一个名为int goalsScored的变量,你该如何按照goalsScored排序呢?HockeyPlayer
对象组成的 Arraylist
。如果它们都有一个名为int goalsScored的变量,你该如何按照goalsScored排序呢?您可以使用Collections.sort
与自定义的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
}
});
比较部分也可以这样写:
players.sort(Comparator.comparingInt(HockeyPLayer::goalsScored));
或者,您可以使HockeyPlayer implements
Comparable<HockeyPlayer>
。这定义了所有HockeyPlayer
对象的自然排序。使用Comparator
更加灵活,因为不同的实现可以按名称、年龄等排序。
return o1.f - o2.f
减法比较快捷方式。大概冰球不是一种可以得分导致问题的运动 =)return p1.goalsScored - p2.goalsScored;
可以被替换为 return Integer.compare(p1.goalsScored,p2.goalsScored);
,以避免在 goalsScored
可能具有负值时发生整数溢出。此外,自 Java 8 开始,此代码可以被替换为 Collections.sort(players, Comparator.comparingInt(h -> h.goalsScored));
。 - Pshemoreturn Long.compare(p1.getLongValue(), p2.getLongValue());
。 - user1318194正如@user6158055所建议的那样,使用Java 8
可以实现一行代码,如下:
Collections.sort(
hockeyPlayerList,
(player1, player2) -> player1.getGoalsScored()
- player2.getGoalsScored());
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 + "]";
}
}
}
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]
只需要一行Java 8代码:
Collections.sort(players, (p1, p2) -> p1.getGoalsScored() - p2.getGoalsScored());
Collections.sort(
people,
(player1, player2) ->
player1.getLastName().compareTo(player2.getLastName())
);
- cammandoCollections.sort(playList, Comparator.comparingInt(HockeyPLayer::goalsScored))
Java 有一组 sort() 方法可以用于这种排序。详见 Collections.sort (和 Comparable)。