Get rid of exceptions you'd ignore anyway

Exceptional is a single class (and some inner classes) that implements methods that make it look very much like an java.util.Optional. But it is not Optional.

Exceptional is a value, which is provided by a supplier (but not a java.util.function.Supplier) which may throw an exception. So when you write

Exceptional.of(() -> throw new Exception()).orElse("Alma")

what you get is "Alma". The major difference from Optional is that the argument of the method of() is a supplier (to be specific an javax0.tools.exceptional.Exceptional.ThrowingSupplier). In case the supplier throws an Exception then the value inside the returned Exceptional object will be "empty".

On an Exceptional object you can call or(), map(), flatMap() and so on. Essentially the same (almost) methods that are defined in the class java.util.Optional. There are some differences though.

The methods that return Optional in the Optional class here return Exceptional. If it is a surprise you probably should not read on.

The static methods of() and ofNullable() and the non-static methods or() and orNullable() accept javax0.tools.exceptional.Exceptional.ThrowingSupplier as argument. (Also note that orNullable() barely exists in Optional if at all.)

The methods map() and flatMap() accept javax0.tools.exceptional.Exceptional.ThrowingFunction as argument. If any of these throw exception the resulting Exceptional will be empty.

These are the non-taxative features raw and uncooked. What is it good for?

You have an old code

// this is a totally made up code, we have never seen anything close
  String clientId = null;
  try {
    clientId = req.getAttribute("klientele");
  }catch(ParseException pe){
  }
  if( clientId == null ){
    clientId = getDebugClient();
  }

Using Exceptional you can

  final String clientId = Exceptional.<String>ofNullable(() -> req.getAttribute("klientele"))
                                     .orNullable(() -> getDebugClient())
                                     .orElse(null);

it is a matter of taste which one you prefer.

You can also replace the good old

  Integer value = part.dev.item(0). ...getter():

prone to NullPointerException to

  Integer value = Exceptional.ofNullable(() -> part.dev.item(0). ...getter()).orElse(null);

if that is more readable.

<dependency>
  <groupId>com.javax0</groupId>
  <artifactId>exceptional</artifactId>
  <version>1.0.0</version>
</dependency>