gradle/gradle · error · IllegalArgumentException

Method %s is not public.

Error message

Method %s is not public.

What it means

Gradle throws this error when the following condition is violated: Method <value> is not public.

Source

Thrown at platforms/core-configuration/model-core/src/main/java/org/gradle/internal/instantiation/managed/DefaultManagedObjectRegistry.java:269

        private static final MethodHandles.Lookup LOOKUP = MethodHandles.publicLookup();

        private final ConcurrentMap<Method, MethodHandle> unreflectionCache = new ConcurrentHashMap<>();
        private final ConcurrentMap<GetMethodKey, Method> findMethodCache = new ConcurrentHashMap<>();

        /**
         * Unreflect the given method, caching the result.
         *
         * @throws IllegalArgumentException if the method is not public or its declaring class is not public.
         */
        public MethodHandle unreflect(Method method) {
            MethodHandle cached = unreflectionCache.get(method);
            if (cached != null) {
                return cached;
            }

            if (!Modifier.isPublic(method.getModifiers())) {
                throw new IllegalArgumentException("Method " + method + " is not public.");
            } else if (!Modifier.isPublic(method.getDeclaringClass().getModifiers())) {
                throw new IllegalArgumentException("Declaring class '" + method.getDeclaringClass().getName() + "' of method " + method + " is not public.");
            }

            return unreflectionCache.computeIfAbsent(method, m -> {
                try {
                    MethodHandle handle = LOOKUP.unreflect(m);
                    return handle.asType(MethodType.methodType(Object.class, handle.type().parameterArray())); // Allows invokeExact
                } catch (IllegalAccessException e) {
                    throw UncheckedException.throwAsUncheckedException(e);
                }
            });
        }

        /**
         * Get the method in the given class with the given signature.
         *
         * @throws RuntimeException if the method cannot be found.

View on GitHub (pinned to 534f27719b)

Solutions

1. Review the values passed to this API and correct the invalid input described in the error message.

When it happens

Trigger: Thrown at platforms/core-configuration/model-core/src/main/java/org/gradle/internal/instantiation/managed/DefaultManagedObjectRegistry.java:269 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of gradle/gradle@534f27719b (2026-08-22). Data as JSON: /api/errors/c430691f1a0085c5. Report an issue: GitHub.