需求:我需要编写一个Jo-Ken-Pô游戏的代码,这个游戏可以和多个玩家一起玩。我需要编写一个Jo-Ken-Pô游戏的代码,这个游戏可以和多个玩家一起玩,有5个角色(SPOCK、剪刀、纸、石头和蜥蜴)。有5个角色(SPOCK、剪刀、纸、石头和蜥蜴)。我可以用这两个链式的when开关来实现(下面的代码使用了when(),因为它是在Kotlin中使用的,但同样的想法也可以在Java中使用switch。
when (u1.play) {
PlayType.SPOCK -> when (u2.play) {
//SPOCK WINS
PlayType.TESOURA -> return u1
PlayType.PEDRA -> return u1
//SPOCK LOSES
PlayType.PAPEL -> return u2
PlayType.LAGARTO -> return u2
}
PlayType.TESOURA -> when (u2.play) {
//TESOURA (scissors) WINS
PlayType.PAPEL -> return u1
PlayType.LAGARTO -> return u1
//TESOURA (scissors) LOSES
PlayType.SPOCK -> return u2
PlayType.PEDRA -> return u2
}
PlayType.PAPEL -> when (u2.play) {
//PAPEL (paper) WINS
PlayType.SPOCK -> return u1
PlayType.PEDRA -> return u1
//PAPEL (paper) LOSES
PlayType.TESOURA -> return u2
PlayType.LAGARTO -> return u2
}
PlayType.PEDRA -> when (u2.play) {
//PEDRA (stone) WINS
PlayType.LAGARTO -> return u1
PlayType.TESOURA -> return u1
//PEDRA (stone) LOSES
PlayType.SPOCK -> return u2
PlayType.PAPEL -> return u2
}
PlayType.LAGARTO -> when (u2.play) {
//LAGARTO (lizard) WINS
PlayType.SPOCK -> return u1
PlayType.PAPEL -> return u1
//LAGARTO (lizard) LOSES
PlayType.TESOURA -> return u2
PlayType.PEDRA -> return u2
}
}
我读了好几个小时的书,试图找到如何使用lambda将这段代码变得更优雅,但我找不到任何线索。请您提供任何帮助,将是非常好的欢迎。
我将整个代码粘贴在这里。虽然你看到我至少使用lambda来调用方法,但我肯定缺少了lambda的一些强大功能,而且几乎是以Java 7< 古典的方式来编码。
所有的用户都来自一个H2数据库。这里是存储库
import com.mycomp.jokenpo.model.User
import org.springframework.data.repository.CrudRepository
interface UserRepository : CrudRepository<User, Long>
用户模式
import com.mycomp.jokenpo.enums.PlayType
import javax.persistence.*
@Entity
data class User(
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
val id: Long,
@Column(nullable = false)
val name: String,
@Enumerated
@Column(nullable = false)
val play: PlayType
)
Enum PlayType
enum class PlayType(val value: Int) {
SPOCK(1), TESOURA(2), LAGARTO(3), PAPEL(4), PEDRA(5)
}
服务 * Here are the issues *
import com.mycomp.jokenpo.enums.PlayType
import com.mycomp.jokenpo.model.User
import com.mycomp.jokenpo.respository.UserRepository
import org.springframework.stereotype.Component
@Component
class GameService(private val userRepository: UserRepository) {
fun returnWinnerBetweenTwoPlayers(u1: User, u2: User): User {
when (u1.play) {
PlayType.SPOCK -> when (u2.play) {
//SPOCK WINS
PlayType.TESOURA -> return u1
PlayType.PEDRA -> return u1
//SPOCK LOSES
PlayType.PAPEL -> return u2
PlayType.LAGARTO -> return u2
}
PlayType.TESOURA -> when (u2.play) {
//TESOURA (scissors) WINS
PlayType.PAPEL -> return u1
PlayType.LAGARTO -> return u1
//TESOURA (scissors) LOSES
PlayType.SPOCK -> return u2
PlayType.PEDRA -> return u2
}
PlayType.PAPEL -> when (u2.play) {
//PAPEL (paper) WINS
PlayType.SPOCK -> return u1
PlayType.PEDRA -> return u1
//PAPEL (paper) LOSES
PlayType.TESOURA -> return u2
PlayType.LAGARTO -> return u2
}
PlayType.PEDRA -> when (u2.play) {
//PEDRA (stone) WINS
PlayType.LAGARTO -> return u1
PlayType.TESOURA -> return u1
//PEDRA (stone) LOSES
PlayType.SPOCK -> return u2
PlayType.PAPEL -> return u2
}
PlayType.LAGARTO -> when (u2.play) {
//LAGARTO (lizard) WINS
PlayType.SPOCK -> return u1
PlayType.PAPEL -> return u1
//LAGARTO (lizard) LOSES
PlayType.TESOURA -> return u2
PlayType.PEDRA -> return u2
}
}
return u1
}
fun playGameWithAll(): User? {
val allUsers = userRepository.findAll().toList()
val winner = allUsers.reduce { a, b ->
returnWinnerBetweenTwoPlayers(a, b)
}
if (allUsers.filter { player -> player.play == winner.play }
.count() == 1)
return winner
else
return null
}
}
上面的代码按预期工作,但我有填充我是不好编码的两个原因。
1 - 我拆分了两个小lambda语句:减少比较对方的playtype和只是为了弄清楚是否有一个以上的赢家,我编码.count分开的
2 - 当然,可能有一个更优雅和更易读的方法来编码两个链式开关与lambda,但我可以得到甚至第一步尝试一下。
PS:代码是Kotlin的,但如果你指出任何Java的东西,我可以很容易地翻译成kotlin。任何诀窍或建议如何重现工厂将高度赞赏。
任何感兴趣的人得到游戏填写免费克隆从 https:/github.comjimisdrpcgames.git。
***在米哈伊尔的回答后编辑。
Main.java
package poc;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.Set;
public class Main {
public static void main(String[] args) {
//Fake returned list from database
List<User> usersList = List.of(
new User(1L, "Jimis", PlayType.LAGARTO),
new User(2L, "Drpc", PlayType.PAPEL));
//User winnerUser = returnWinnerBetweenTwoPlayers(usersList.get(0), usersList.get(1));
Optional<User> winnerUser = usersList.stream().reduce( (a, b) ->
returnWinnerBetweenTwoPlayers(a , b));
System.out.print(winnerUser);
}
//Trying to refactoring from classical switch to some structure for using with lambda
private final static Map<PlayType, Set<PlayType>> CONFIG = Map.of(
PlayType.SPOCK,
Set.of(PlayType.TESOURA, PlayType.PEDRA),
PlayType.TESOURA,
Set.of(PlayType.PAPEL, PlayType.LAGARTO)
);
private static User returnWinnerBetweenTwoPlayers(User u1, User u2) {
/// ****** Exception next line
if (CONFIG.get(u1.getPlay()).contains(u2.getPlay())) {
return u1;
}
return u2;
}
}
用户模式
package poc;
public class User {
Long id;
String name;
PlayType play;
public User(Long id, String name, PlayType play) {
super();
this.id = id;
this.name = name;
this.play = play;
}
//... getters/setters removed
}
PlayType enum
package poc;
public enum PlayType {
SPOCK,
TESOURA,
PEDRA,
PAPEL,
LAGARTO;
}
运行这部分时出现异常 CONFIG.get(u1.getPlay()).包含(u2.getPlay()
Exception in thread "main" java.lang.NullPointerException
at moduleinfo/poc.Main.returnWinnerBetweenTwoPlayers(Main.java:39)
at moduleinfo/poc.Main.lambda$0(Main.java:21)
at java.base/java.util.stream.ReduceOps$2ReducingSink.accept(ReduceOps.java:123)
at java.base/java.util.AbstractList$RandomAccessSpliterator.forEachRemaining(AbstractList.java:720)
at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:484)
at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:474)
at java.base/java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:913)
at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
at java.base/java.util.stream.ReferencePipeline.reduce(ReferencePipeline.java:558)
at moduleinfo/poc.Main.main(Main.java:20)
如果我尝试简化并调用没有stream().reduce()的情况下,我在相同的点得到了这个问题。
Exception in thread "main" java.lang.NullPointerException
at moduleinfo/poc.Main.returnWinnerBetweenTwoPlayers(Main.java:49)
at moduleinfo/poc.Main.main(Main.java:19)
*** 最终解决方案
public class Main {
public static void main(String[] args) {
//Fake returned list from database
List<User> usersList = List.of(
new User(1L, "Jogador 1", PlayType.PEDRA),
new User(2L, "Jogador 2", PlayType.TESOURA),
new User(3L, "Jogador 3", PlayType.TESOURA),
new User(4L, "Jogador 4", PlayType.SPOCK)
);
Optional<User> winnerUser = usersList.stream().reduce( (a, b) ->
returnWinnerBetweenTwoPlayers(a , b));
System.out.print(winnerUser.get().getName());
}
private final static Map<PlayType, Set<PlayType>> CONFIG = Map.of(
PlayType.SPOCK,
Set.of(PlayType.TESOURA, PlayType.PEDRA),
PlayType.TESOURA,
Set.of(PlayType.PAPEL, PlayType.LAGARTO),
PlayType.PAPEL,
Set.of(PlayType.SPOCK, PlayType.PEDRA),
PlayType.PEDRA,
Set.of(PlayType.LAGARTO, PlayType.TESOURA),
PlayType.LAGARTO,
Set.of(PlayType.SPOCK, PlayType.PAPEL)
);
private static User returnWinnerBetweenTwoPlayers(User u1, User u2) {
if (CONFIG.get(u1.getPlay()).contains(u2.getPlay())) {
return u1;
}
return u2;
}
}
这个 switch inside switch
构造看起来真的很难读懂,你是对的。
你可以这样想:每个PlayType从其他一些类型中胜出。而这些信息看起来就像一个配置,所以可以用一种声明式的方式来描述,就像这样。
所以你可以直接定义一个 Map<PlayType, Set<PlayType>>
并验证是否 u2.play is contained by map.get(u1.play)
UPD. 代码示例(java,用记事本写的,所以可能包含一些语法错误)
class GameService {
private final static Map<PlayType, Set<PlayType>> CONFIG = Map.of(
PlayType.SPOCK, Set.of(PlayType.TESOURA, PlayType.PEDRA),
PlayType.TESOURA, Set.of(PlayType.PAPEL, PlayType.LAGARTO)
//etc
);
function User returnWinnerBetweenTwoPlayers(User u1, User u2){
if (CONFIG.get(u1.getType()).contains(u2.getType()){
return u1;
}
return u2;
}
}