import java.util.Collection;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.Map;
import org.checkerframework.checker.nullness.qual.Nullable;
import org.checkerframework.dataflow.qual.Pure;

class Other {
    public static final class StaticIterator<T> implements Iterator<T> {
        Enumeration<T> e;

        public StaticIterator(Enumeration<T> e) {
            this.e = e;
        }

        public boolean hasNext() {
            return e.hasMoreElements();
        }

        public T next() {
            return e.nextElement();
        }

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

    public final class FinalIterator<T> implements Iterator<T> {
        Enumeration<T> e;

        public FinalIterator(Enumeration<T> e) {
            this.e = e;
        }

        public boolean hasNext() {
            return e.hasMoreElements();
        }

        public T next() {
            return e.nextElement();
        }

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

class Entry<K, V> implements Map.Entry<K, V> {
    public V setValue(V newValue) {
        throw new RuntimeException();
    }

    @SuppressWarnings("purity") // new and throw are not allowed, ignore
    @Pure
    public K getKey() {
        throw new RuntimeException();
    }

    @SuppressWarnings("purity") // new and throw are not allowed, ignore
    @Pure
    public V getValue() {
        throw new RuntimeException();
    }
}

interface Function<F, T extends @Nullable Object> {
    T apply(@Nullable F from);

    @Pure
    boolean equals(@Nullable Object obj);
}

enum IdentityFunction implements Function<Object, @Nullable Object> {
    INSTANCE;

    public @Nullable Object apply(@Nullable Object o) {
        return o;
    }
}

abstract class FilteredCollection<E> implements Collection<E> {
    public boolean addAll(Collection<? extends E> collection) {
        for (E element : collection) {}
        return true;
    }
}
