quarkusio/quarkus · error · UnsupportedOperationException

UnsupportedOperationException

Error message

UnsupportedOperationException

What it means

The iterator returned by ImmutableSubstringMap's values/lookup does not support element removal: calling remove() on it unconditionally throws UnsupportedOperationException. This is an immutable snapshot structure, so mutation through the iterator is intentionally unsupported.

Source

Thrown at extensions/vertx-http/runtime/src/main/java/io/quarkus/vertx/http/runtime/security/ImmutableSubstringMap.java:222

                        }

                        @Override
                        public String next() {
                            if (!hasNext()) {
                                throw new NoSuchElementException();
                            }
                            String ret = (String) map[pos];

                            pos += 2;
                            while (pos < table.length && tMap[pos] == null) {
                                pos += 2;
                            }
                            return ret;
                        }

                        @Override
                        public void remove() {
                            throw new UnsupportedOperationException();
                        }
                    };
                }
            };

        }

        ImmutableSubstringMap<V> build() {
            return new ImmutableSubstringMap<>(table);
        }
    }
}

View on GitHub (pinned to e1c734241f)

Solutions

1. Do not call remove() on this iterator; build a new ImmutableSubstringMap without the unwanted entries instead.
2. Collect the keys/values you want to drop and rebuild the map.
3. If mutation is required, use a mutable Map during construction before wrapping in ImmutableSubstringMap.

Example fix

// before
it.remove();
// after
Map<String,V> copy = new HashMap<>(existing);
copy.remove(key);
ImmutableSubstringMap<V> updated = rebuild(copy);

// avoid mutation: do not call remove() on ImmutableSubstringMap iterators

try (var it = map.iterator()) {
  while (it.hasNext()) { process(it.next()); }
} catch (UnsupportedOperationException e) {
  // snapshot iterator: rebuild map without the entry instead of removing
}

When it happens

Trigger: Calling Iterator.remove() on an iterator obtained from ImmutableSubstringMap (e.g. while iterating its values) or any library code that tries to mutate through it.

Common situations: Developers porting mutable-map iteration code, or trying to prune entries while iterating a read-only lookup structure.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

• Stateless operations not supported
• This isn't used for schema generation - see SessionFactoryOb
• This method is not available at runtime in Quarkus
• Use the 'OidcClientCommonConfigBuilder.CredentialsBuilder#bu
• Cannot call a page related method, call page(Page) or page(i

AI-assisted analysis of quarkusio/quarkus@e1c734241f (2026-09-05). Data as JSON: /api/errors/f43ecec986daf553. Report an issue: GitHub.