Java 8 optional ifPresent return object orElseThrow exception

Question

I m trying to make something like this    private String getStringIfObjectIsPresent Optional lt Object gt  object           object ifPresent    - gt               String result    result                 some logic with result and return it             return result             orElseThrow MyCustomException  new           This won t work  because ifPresent takes Consumer functional interface as parameter  which has void accept T t   It cannot return any value  Is there any other way to do it

User · Answer

Use the map-function instead  It transforms the value inside the optional   Like this   private String getStringIfObjectIsPresent Optional lt Object gt  object        return object map    - gt            String result    result             some logic with result and return it         return result         orElseThrow MyCustomException  new

User · Answer

Actually what you are searching is  Optional map  Your code would then look like   object map o - gt   result     or your function            orElseThrow MyCustomException  new     I would rather omit passing the Optional if you can  In the end you gain nothing using an Optional here  A slightly other variant   public String getString Object yourObject      if  Objects isNull yourObject        or use requireNonNull instead if NullPointerException suffices      throw new MyCustomException          String result            your string mapping function   return result      If you already have the Optional-object due to another call  I would still recommend you to use the map-method  instead of isPresent  etc  for the single reason  that I find it more readable  clearly a subjective decision  -

User · Answer

Two options here   Replace ifPresent with map and use Function instead of Consumer  private String getStringIfObjectIsPresent Optional lt Object gt  object        return object              map obj - gt                    String result    result                     some logic with result and return it                 return result                              orElseThrow MyCustomException  new       Use isPresent   private String getStringIfObjectIsPresent Optional lt Object gt  object        if  object isPresent              String result    result             some logic with result and return it         return result        else           throw new MyCustomException

User · Answer

I d prefer mapping after making sure the value is available  private String getStringIfObjectIsPresent Optional lt Object gt  object       Object ob   object orElseThrow MyCustomException  new          do your mapping with ob    String result   your-map-function ob     return result      or one liner  private String getStringIfObjectIsPresent Optional lt Object gt  object       return your-map-function object orElseThrow MyCustomException  new

[java] Java 8 optional: ifPresent return object orElseThrow exception

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