How to solve the deep copying problem (mutating list elements via AtomicInteger.incrementAndGet)?

The issue of deep copying when mutating list elements with AtomicInteger.incrementAndGet() is related to the fact that when copying the list, references to objects are copied, not the objects themselves. Therefore, changes in one list are reflected in the other.

To solve this problem, you need to implement deep copying of elements by creating new AtomicInteger objects with the same values, for example:

List<AtomicInteger> original = ...;
List<AtomicInteger> deepCopy = original.stream()
    .map(ai -> new AtomicInteger(ai.get()))
    .collect(Collectors.toList());

Now, changes in deepCopy will not affect original.

Thus, each element is copied by value, not by reference, preventing unwanted mutation of the original data.