Check out example codes for "java 8 iterating and manipulating list". It will help you in understanding the concepts better.

Code Example 1

childrenList.stream()
            .map(this::convertChildToPerson)
            .forEachOrdered(personList::add);

Code Example 2

List<Person> newList = childrenList.stream()
             .map(this::convertChildToPerson)
             .collect(Collectors.toList());

 personList.addAll(newList);

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