Java AbstractList.addAll() is a method in the Java AbstractList class that adds all elements from another collection to the current list. If the collection is not empty, it extends the list by appending the elements. Introduced in Java 1997 with Java 1.2, addAll() is frequently used in applications where you need to merge two collections or build a larger list from smaller ones.

https://docs.oracle.com/javase/8/docs/api/java/util/AbstractList.html