Riešenia vybraných úloh z cvičení č. 5

Úloha č. 5

import java.util.*;

public class ElementSubsetIterator<E> implements Iterator<E> {
    private Iterator<E> iterator;
    private Set<E> elements;
    private E next;
    private boolean hasNext;

    public ElementSubsetIterator(Iterator<E> iterator, Set<E> elements) {
        this.iterator = iterator;
        this.elements = new HashSet<>(elements);
        findNext();
    }

    private void findNext() {
        hasNext = false;
        while (iterator.hasNext() && !hasNext) {
            E element = iterator.next();
            if (elements.contains(element)) {
                hasNext = true;    
                next = element;
            }
        }
    }

    @Override
    public boolean hasNext() {
        return hasNext;
    }

    @Override
    public E next() {
        if (hasNext()) {
            E result = next;
            findNext();
            return result;
        } else {
            throw new NoSuchElementException();
        }
    }
}

Úloha č. 6

import java.util.*;

public class PalilalicIterator<E> implements Iterator<E> {
    private Iterator<E> iterator;
    private boolean emitted;
    private E last;

    public PalilalicIterator(Iterator<E> iterator) {
        this.iterator = iterator;
    }

    @Override
    public boolean hasNext() {
        return emitted || iterator.hasNext();
    }

    @Override
    public E next() {
        if (emitted) {
            emitted = false;
            return last;
        } else {
            last = iterator.next();
            emitted = true;
            return last;
        }
    }
}