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PatPanda
Asked: 2024-07-15 17:30:56 +0800 CST

问题重构 if-else-if string.contains(“X”) 以切换大小写（或更好）

  • 772
  • 包括有关您的目标的详细信息：

我想重构if-else-if string.contains("X")Java 中的语句来切换大小写或 Map。

  • 显示一些代码：

我有一段代码，非常简单，如下所示：

     public String question(String sentence) {
        if (sentence.contains("eat")) {
            return getFoodFromSentence(sentence);
        } else if (sentence.contains("drink")) {
            return getBeverageFromSentence(sentence);
        } else if (sentence.contains("drive")) {
            return getVehicleFromSentence(sentence);
        } else if (sentence.contains("travel")) {
            return getDestinationFromSentence(sentence);
    [...
        many many other else if
    ...]
        } else {
            return "sentence with unknown verb";
        }
    }

    private String getDestinationFromSentence(String sentence) {
        return ""; //some complex code to extract some info from the sentence
    }

    private String getVehicleFromSentence(String sentence) {
        return ""; //some complex code to extract some info from the sentence
    }
[... all the other actual handling methods ]

我希望使用 switch case 来重构它：

  • 描述一下我的尝试：

使用 switch case：

   public String question(String sentence) {
        switch (???) { //issue here, I am not able to come up with the expression
            case (sentence.contains("eat")): // issue here, I am not able to have the cases representing the if
                return getFoodFromSentence(sentence);
            case (sentence.contains("drink")):
                return getBeverageFromSentence(sentence);
            case (sentence.contains("drive")):
                return getVehicleFromSentence(sentence);
            case (sentence.contains("travel")):
                return getDestinationFromSentence(sentence);
        [ ... the other case conditions ... ]
            default:
                return "sentence with unknown verb";
        }
    }

我也尝试使用 Map 模式，例如：

 public String question(String sentence) {
        Map<Predicate<String>, Function<String, String>> map =
                Map.of(s -> s.contains("eat"), s -> getFoodFromSentence(s),
                        s -> s.contains("drink"), s -> getBeverageFromSentence(s),
                        s -> s.contains("drive"), s -> getVehicleFromSentence(s),
                        s -> s.contains("travel"), s -> getDestinationFromSentence(s));
        return map.get(???).apply(sentence); // issue here, how to get the correct key of the map?
    }
  • 问题：

请问使用 switch case 的问题该如何解决？

或者也许如何解决地图问题？

还有其他技术可以重构这个吗 if-else-if string.contains("X")？

java

3 个回答

  1. 对于基于地图的方法，您可以尝试以下方法：

    public String question(String sentence) {
    Map<String, Function<String, String>> map = Map.of(
            "eat", this::getFoodFromSentence,
            "drink", this::getBeverageFromSentence,
            "drive", this::getVehicleFromSentence,
            "travel", this::getDestinationFromSentence
    );
    for (Map.Entry<String, Function<String, String>> entry : map.entrySet()) {
        if (sentence.contains(entry.getKey())) {
            return entry.getValue().apply(sentence);
        }
    }
    return null;
}
    • 2
  2. Best Answer

    case语句可以使用when关键字：

    public String question(String sentence) {
    switch (sentence) {
        case String s when sentence.contains("eat"):
            return getFoodFromSentence(sentence);
        case String s when sentence.contains("drink"):
            return getBeverageFromSentence(sentence);
        case String s when sentence.contains("drive"):
            return getVehicleFromSentence(sentence);
        case String s when sentence.contains("travel"):
            return getDestinationFromSentence(sentence);
        default:
            return "sentence with unknown verb";
    }
}
    • 2

  3. 与 tobias_k 的 map 方法类似的解决方案仅使用 LinkedHashMap 来保证顺序，并使用流和可选项来稍微提高可读性：

    import java.util.LinkedHashMap;
import java.util.Map;
import java.util.function.UnaryOperator;

public class Example {

    public static void main(String[] args) {

        Example ex = new Example();

        String sentence1 = "What do you eat?";
        System.out.println(ex.question(sentence1));

        String sentence2 = "What do you drink?";
        System.out.println(ex.question(sentence2));

        String sentence3 = "What do you drive?";
        System.out.println(ex.question(sentence3));

        String sentence4 = "Where do you travel to?";
        System.out.println(ex.question(sentence4));

        String sentence5 = "What did you do yesterday?";
        System.out.println(ex.question(sentence5));
    }

    public String question(String sentence) {

        Map<String, UnaryOperator<String>> map = new LinkedHashMap<>();
        map.put("eat",    this::getFoodFromSentence);
        map.put("drink",  this::getBeverageFromSentence);
        map.put("drive",  this::getVehicleFromSentence);
        map.put("travel", this::getDestinationFromSentence);

        return map.keySet().stream()
                           .filter(sentence::contains)
                           .findFirst()
                           .map(e -> map.get(e).apply(sentence))
                           .orElse("Sentence with unknown verb");
    }

    private String getFoodFromSentence(String sentence) {
        return "Haggis";
    }

    private String getBeverageFromSentence(String sentence) {
        return "IRN-BRU";
    }

    private String getDestinationFromSentence(String sentence) {
        return "Ring of Brodgar";
    }

    private String getVehicleFromSentence(String sentence) {
        return "Galloway";
    }
}
    • 1

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