public class Collectors {
    public interface ProvidedCollector<T> extends Collector<T> {
        boolean isProvidedBy(Provider<?> provider);
    }

    public static class SingleElement<T> implements Collector<T> {
        private final T element;

        public SingleElement(T element) {
            this.element = element;
        }

        @Override
        public boolean calculatePresence(ValueConsumer consumer) {

import org.gradle.api.internal.provider.Collectors.ElementFromProvider;
import org.gradle.api.internal.provider.Collectors.ElementsFromCollectionProvider;
import org.gradle.api.internal.provider.Collectors.SingleElement;
import org.gradle.api.internal.provider.Collectors.TypedCollector;
import org.gradle.api.internal.provider.ProviderInternal;
import org.gradle.api.specs.Spec;
import org.gradle.internal.Cast;

import org.gradle.api.internal.provider.Collectors.ElementsFromCollection;
import org.gradle.api.internal.provider.Collectors.ElementsFromCollectionProvider;
import org.gradle.api.internal.provider.Collectors.SingleElement;
import org.gradle.api.provider.HasMultipleValues;
import org.gradle.api.provider.Provider;
import org.gradle.internal.Cast;
import org.gradle.util.internal.TextUtil;

import javax.annotation.Nonnull;