ConcurrentModificationException

导致此错误的原因

A structural modification (add, remove) is made to a collection during iteration using a for-each loop or an iterator. This can happen in single-threaded code when modifying a collection inside its own loop.

如何修复

Use Iterator.remove() to safely remove elements during iteration. Use ConcurrentHashMap or CopyOnWriteArrayList for concurrent access. Collect items to remove in a separate list and remove after iteration.

for (String s : list) {
  list.remove(s); // CME
}