因此,我在这里要求用户输入击打,站立,投降或退出的信息。我将它们与NOTVALID一起作为枚举。
enum Decisions
{
HIT, STAND, SURRENDER, QUIT, PLAY, NOTVALID;
// NOTVALID is used to re-ask to play again
}
因此,如果用户放置例如“ blah”而不是有效选项之一,则我希望它将其视为NOTVALID,并在switch语句中执行用于NOTVALID的代码。我怎样才能做到这一点?照原样,当我运行程序时,它会返回错误:
Exception in thread "main" java.lang.IllegalArgumentException: No enum constant BlackJack.Decisions.BLAH
我该怎么做才能使NOTVALID成为其他枚举之一以外的任何东西?
System.out.println("Do you want to hit, stand, surrender, or quit?");
String decisionInput;
decisionInput = keyboard.nextLine().toUpperCase();
decision = Decisions.valueOf(decisionInput);
switch (decision)
{
case HIT:
Random playerCard = new Random();
cardPick = playerCard.nextInt(13);
playerSum = playerSum + getCardValue(cardPick);
System.out.println("Card: " + (Card.values()[cardPick]) + ". The sum of your hand is: " + playerSum + ".");
System.out.println("The hole card was " + (Card.values()[cardPick2]) + ". The house has: " + houseSum + ".");
findWinner(playerSum, houseSum, decision);
System.out.println("Do you want to play again? Type PLAY or QUIT.");
decision = Decisions.valueOf(keyboard.nextLine().toUpperCase());
break;
case STAND:
case SURRENDER:
findWinner(playerSum, houseSum, decision);
System.out.println("Do you want to play again? Type PLAY or QUIT.");
decision = Decisions.valueOf(keyboard.nextLine().toUpperCase());
break;
case QUIT:
System.out.println("Thanks for playing!");
System.exit(0);
break;
case NOTVALID:
System.out.println("Invalid input. Try again: hit, stand, surrender, or quit?");
decision = Decisions.valueOf(keyboard.nextLine().toUpperCase());
}
}
}
}
定义一个新方法,该方法NOTVALID
为无法识别的输入返回。最简洁的方法是捕获这样抛出的IllegalArgumentException。
enum Decisions{
HIT, STAND, SURRENDER, QUIT, PLAY, NOTVALID;
public static Decisions asDecision(String input) {
try {
return Decisions.valueOf(input);
} catch(IllegalArgumentException e) {
return Decisions.NOTVALID;
}
}
}
如果那样冒犯了您使用的敏感性try..catch
,则您可以自己手动进行操作。
enum Decisions{
HIT, STAND, SURRENDER, QUIT, PLAY, NOTVALID;
public static Decisions asDecision(String input) {
for(Decisions d : values()) {
if(d.name().toLowerCase().equals(input.toLowerCase()) {
return d;
}
}
return Decisions.NOTVALID;
}
}
无论哪种方式,请改用new方法。
在不被允许定义新方法的情况下,您可以将您的分配括在中try..catch
,如下所示:
String decisionInput;
decisionInput = keyboard.nextLine().toUpperCase();
try{
decision = Decisions.valueOf(decisionInput);
} catch(IllegalArgumentException e){
decision = Decisions.NOTVALID;
}
// Rest of your code...
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