How can it be determined how the size of an array changes when elements are added or removed?

In Java, arrays have a fixed size after creation, so their capacity does not change dynamically. To work with a variable number of elements, collections such as ArrayList are used.

In the case of ArrayList, when adding elements, the internal array increases automatically, usually with some extra capacity to reduce the number of reallocations. When removing elements, the size of the internal array may decrease, but not always immediately.

To determine how the capacity of the array inside ArrayList changes, reflection can be used to access the private field elementData or behavior can be monitored through profiling.

Example:

ArrayList<Integer> list = new ArrayList<>();
list.add(1);
list.add(2);
// The internal array increased if the limit was reached

list.remove(0);
// The size of the list decreased, but the internal array may remain the same

For regular arrays, the size is fixed, so when adding or removing elements, a new array with the required size is created and data is copied.