Merge lists with addAll(..)
List<MyClass> mergedList = new ArrayList<>();
mergedList.addAll(list1);
mergedList.addAll(list2);
mergedList.addAll(list3);
Merge lists in Java 8
List<MyClass> mergedList = Stream.of(list1, list2, list3)
.flatMap(item -> item.stream())
.collect(Collectors.toList());
You may also find these posts interesting: