如何用更好的解决方案替换 switch 语句 - 干净的代码提示

I created a code, which have to convert ContentDataType into MIME types. For example - ContentDataType is a simple String like ImageJPEG and now I use MediaType.IMAGE_JPEG_VALUE to convert it into image/jpeg. But I use switch to do this. This is a code:

 public static String createContentType(ContentDataType contentDataType) {
        String contentType;

        switch (contentDataType) {          
            case IMAGE_JPG:
                contentType = MediaType.IMAGE_JPEG_VALUE;
                break;
            //next media types
        }
    return contentType;
 }

有什么更好更优雅的方法来做到这一点?我不想使用 if，但可能有一些多态性?你能给我一些提示吗?

private static Hashtable<String, String> types = new Hashtable<>();

static{
    types.put(IMAGE_JPG, MediaType.IMAGE_JPEG_VALUE);
    types.put(IMAGE_PNG, MediaType.IMAGE_PNG_VALUE);
    types.put(IMAGE_XXX, MediaType.IMAGE_XXX_VALUE);
}

public static String createContentType(ContentDataType contentDataType) {
    if types.containsKey(contentDataType) 
        return types.get(contentDataType);
    else
        throw new RuntimeException("contentDataType not supported");
    }
}