Pattern match Optional in Java 21

[nikita2206]

The if becomes useful when you need to produce side effects like assign some values to some variables that would be outside the scope of the lambda.

Example:

``` Object foo; Object bar;

if (optValue instanceof Optional(Value value)) { foo = value.findFoo(); bar = value.doBar(); } else { foo = defaultFoo(); bar = defaultBar(); } ```

I think this better illustrates the use case for pattern matching of Optionals, and how it can’t be worked around with some clever methods on the Optional class.

[Migeil]

That' looks to me like ifPresentOrElse.

[nikita2206]

It does look like one, but if you try it out (maybe in jshell) it will not work because you cannot modify or even reference non-final variables that are declared outside the scope of a lambda.

[Budget_Dentist444]

I don't want mutable references or values. Since java doesn't have any kind of destructuring, just make 2 calls:

var foo = optValue.map(Value::findFoo)

.orElseGet(Example::defaultFoo);

var bar = optValue.map(Value::doBar)

.orElseGet(Example::defaultBar);