If a value is present, returns the value, otherwise throws an exception produced by the exception supplying function.

Parameters:

<X>		Type of the exception to be thrown
exceptionSupplier		the supplying function that produces an exception to be thrown

Returns:  the value, if present

Exceptions:

X		if no value is present
NullPointerException		if no value is present and the exception supplying function is null

@apiNote A method reference to the exception constructor with an empty argument list can be used as the supplier. For example, IllegalStateException::new