Java 9 High Performance

The new factory methods in action

After revisiting the existing methods of collection creation, we can now review and enjoy the related API introduced in Java 9. As in a previous section, we start with the List interface. Here is how simple and consistent the immutable list creation can be using the new List.of() factory method:

List<String> immutableList =   List.of("immutableList: Life",       " is", " is", " good!\n\n"); //, null);//immutableList.set(2, "sad.");    //throws exception//immutableList.add("Well...");    //throws exceptionimmutableList.stream().forEach(System.out::print);

As you can see from the previous code comments, the new factory method does not allow including null as the list value.

The immutableSet creation looks similar to this: ...