What type of structure is best to ensure thread safety when infrequently updating list elements?

To ensure thread safety during rare updates of list elements in Java, the CopyOnWriteArrayList data structure is well suited.

Features of CopyOnWriteArrayList:

• Each modification (addition, removal) creates a new copy of the internal array.
• Reading occurs without locks, which is very efficient for frequent reads and rare writes.

Example of usage:

import java.util.concurrent.CopyOnWriteArrayList;

CopyOnWriteArrayList<String> list = new CopyOnWriteArrayList<>();
list.add("element1");
list.add("element2");

// Thread-safe reading
for (String s : list) {
    System.out.println(s);
}

Thus, CopyOnWriteArrayList is suitable when updates are infrequent, and reads are frequent, providing safety without complex synchronization.