Какой hash-код возвращает метод hashCode() для списка по умолчанию?

In Java (and consequently in Android), the hashCode() method for a list (for example, ArrayList) is implemented to return a hash code that depends on the contents of the list. By default, if the standard List implementation from Java collections is used, hashCode() is computed as a combination of the hash codes of all elements in the list in their order.

Specifically, for a List from java.util, the hash code is calculated using the formula:

int hashCode = 1;
for (E e : list)
    hashCode = 31 * hashCode + (e == null ? 0 : e.hashCode());

This means that if you change the contents of the list, its hash code will also change. This approach allows lists to be used in hash tables and other data structures where the hash code based on the content is important.

As for the "default" in the sense of the base Object.hashCode() method, it returns a hash code based on the memory address of the object, but for collections, this method is overridden to consider the contents.