java: Use Optional<T> to indicate optional values

[mpkorstanje]

Permanently avoid the problems from cucumber/cucumber-jvm#2454

[mpkorstanje]

@aslakhellesoy in Javascript buildNumber is not optional:

https://github.com/cucumber/ci-environment/blob/main/javascript/src/types.ts#L4

However the value is evaluated from an expression and may be null. Which one is correct?

[aslakhellesoy]

Great!! This will teach me to use Optional :-)

[aslakhellesoy]

@aslakhellesoy in Javascript buildNumber is not optional:

https://github.com/cucumber/ci-environment/blob/main/javascript/src/types.ts#L4

However the value is evaluated from an expression and may be null. Which one is correct?

Good catch. I think we should allow null for that field. Working on a fix...

[aslakhellesoy]

@aslakhellesoy in Javascript buildNumber is not optional:
https://github.com/cucumber/ci-environment/blob/main/javascript/src/types.ts#L4
However the value is evaluated from an expression and may be null. Which one is correct?

Good catch. I think we should allow null for that field. Working on a fix...

Fixed in #51

[mpkorstanje]

Great!! This will teach me to use Optional :-)

It's relatively simple. Only ever use it as a return type. Don't use it as an argument. When used as a return type, never return null.

https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/Optional.html