NoClassDefFoundError within anonymous class when proguarded

Problematic code

    private final List<Listener> listeners = new ArrayList<>();

    @Override
    public void addListener(Listener listener) {
        if (listener == null || listeners.contains(listener))
            throw new IllegalStateException();

        listeners.add(listener);
    }

    @Override
    public void removeListener(Listener listener) {
        if (listener == null || !listeners.contains(listener))
            throw new IllegalStateException();

        listeners.remove(listener);
    }

    public interface Listener {
        void started(Exercise exercise);
    }

    private final Listener notifier = new Listener() {
        @Override
        public void started(Exercise exercise) {
            listeners.forEach(listener -> listener.started(exercise)); // <-- throws NoClassDefFoundError (on proguard)
        }
    };

This works

Instead of listeners.forEach(listener -> listener.started(exercise));, if we iterate like below it works even with proguard:

            for (Listener listener : listeners) {
                listener.started(exercise);
            }

Config

classpath 'me.tatarka:gradle-retrolambda:3.5.0' // in project build.gradle
apply plugin: 'me.tatarka.retrolambda' // last entry in app build.gradle

// https://github.com/orfjackal/retrolambda/issues/25
retrolambda {
      jvmArgs '-noverify'
}

retrolambdaConfig 'net.orfjackal.retrolambda:retrolambda:2.5.1' // within app dependencies. Even without this got the same error.

[technoir42]

@rpattabi I think you might be getting NoClassDefFoundError because Iterable.forEach takes an instance of Consumer interface which is only available on API 24+. That seems like pretty normal behaviour because Retrolambda does not backport any Java 8 APIs.

[rpattabi]

Are you building for nougat only?

No. I have min sdk: 16 and target sdk: 24.

forEach takes an argument (java.util.function.Consumer<? super T> action), and that for anything less than Nougat the class won’t exist

I see what you mean. This code compiles which is surprising to me. I guess it is due to latest build tools I am using.

Thanks for the work around. I will close this issue since retrolambda or gradle-retrolambda doesn’t have anything to do here.