Migration tips to new Java 8/9 API ?

[Durim Kryeziu]

Hi Ken,

Congrats for the book!

Do you have tips & tricks how to migrate to the new Java 8/9 API from a more legacy Java code ? Like to move from loops and Iterators to Streams, to use Optional properly on the method return types etc ?

Thanks

[Campbell Ritchie]

Durim Kryeziu wrote:. . . to use Optional properly on the method return types etc ?

Thanks

And what will happen if you change the return types of methods in a public API?

[Pete Letkeman]

One item which you may find helpful when doing migration is default methods inside of interfaces as noted here:
https://docs.oracle.com/javase/tutorial/java/IandI/defaultmethods.html

Official Oracle Trail wrote:Default methods enable you to add new functionality to the interfaces of your libraries and ensure binary compatibility with code written for older versions of those interfaces.

[Durim Kryeziu]

Campbell Ritchie wrote:

Durim Kryeziu wrote:. . . to use Optional properly on the method return types etc ?

Thanks

And what will happen if you change the return types of methods in a public API?

I meant newly created methods, maybe I stated it wrong, I meant like, if before I wrote a method like this and that, from now on, it's better to write it this way (with Optionals in this case)! Now I think you got the idea what I meant with that

[Kenneth A. Kousen]

IntellIJ IDEA has many refactoring methods available to help migration. For example, they allow you to convert a regular loop with an if statement that puts the results into a collection into a stream/collect combination. There are many more available, too.

That said, I don't spend a lot of time converting legacy code unless I was already planning to refactor it. Still, it's easy enough to do with the right tools. This is especially useful when you can convert to library calls, like changing your own hand-crafted comparators into simple combinations of Comparator.comparing().thenComparing() chains.