When and why does List remove(Object object) return false

Question

When and why does the method boolean java.util.List.remove(Object object) return false?

The documentation states

[The method ret

Answer 1

from this doc

Removes the first occurrence of the specified element from this list, if it is present (optional operation). If this list does not contain the element, it is unchanged. More formally, removes the element with the lowest index i such that (o==null ? get(i)==null : o.equals(get(i))) (if such an element exists). Returns true if this list contained the specified element (or equivalently, if this list changed as a result of the call).