UnsupportedOperationExceptionis thrown in implementations of such methods. Emphasis on "individual" elements or entries means that
clear()operation is allowed. See exact list of allowed and disallowed operations for
Think about updatable containers as "non-decreasing", which could be "reset"
from time to time by calling
In real practice individual element or entry removals are often not needed. On the other hand, prohibition of removals permits faster implementation of hash table-based containers and iterators over many data structures.