java - 内联开关语句java？

Question

有没有办法在 java 中实现内联 switch 语句？

现在，我正在使用以下内容:

    private static String BaseURL = (lifeCycle == LifeCycle.Production)
        ? prodUrl
        : ( (lifeCycle == LifeCycle.Development)
            ? devUrl
            : ( (lifeCycle == LifeCycle.LocalDevelopment)
                  ? localDevUrl
                  : null
            )
        );

如果我能做这样的事情，我会更喜欢它:

    private static String BaseURL = switch (lifeCycle) {
        case Production: return prodUrl;
        case Development: return devUrl;
        case LocalDevelopment: return localDevUrl;
    }

---

I do know you could achieve this by moving the BaseURL variable into a function GetBaseURL where the switch occurs (see below), however I'm more so just curious if this feature even exists in Java.

static String GetBaseURL() {
    switch(lifeCycle) {
        case Production: return prodUrl;
        case Development: return devUrl;
        case LocalDevelopment: return localDevUrl;
    }

    return null;
} 

---

我正在从 Swift 过渡，在 Swift 中我知道你可以这样做:

private static var BaseURL:String {
    switch (API.LifeCycle) {
        case .Production:
            return prodUrl
        case .Development:
            return devUrl
        case .LocalDevelopment:
            return localDevUrl
    }
}

Answer 1

假设 LifeCycle 是一个 enum，那么你很幸运，因为 switch expressions在 JDK 12 中作为预览功能引入。通过使用它们，您的代码将如下所示:

LifeCycle lifeCycle = ...;

String baseURL = switch (lifeCycle) {
    case Production -> prodUrl;
    case Development -> devUrl;
    case LocalDevelopment -> localDevUrl;
};

如果 LifeCycle 枚举包含的值多于这三个值，那么您需要添加一个 default 案例；否则，将是一个编译时错误。