filteriterator hasnext() and next() function

Question

aprogrammer · Accepted Answer

public class FilterIterator {
    private Predicate pred;
    private Iterator iter;

    private T cachedNext;
    private boolean hasCached = false;

    FilterIterator(Iterator i, Predicate p) {
        iter = i;
        pred = p;
    }

    public boolean hasNext() {
        if (hasCached)
            return true;

        while (iter.hasNext()) {
            T tmp = iter.next();
            if (pred.evaluate(tmp)) {
                setCache(tmp);
                break;
            }
        }

        return hasCached;
    }

    public T next() {
        if (! hasNext())
            throw new NoSuchElementException();

        return getCache();
    }

    private T getCache() {
        hasCached = false;
        return cachedNext;
    }

    private void setCache(T tmp) {
        hasCached = true;
        cachedNext = tmp;
    }

    public static void main(String [] args) {
        List ls = Arrays.asList("Test", "Hello", "World",
                "This is a long string");
        FilterIterator fi = new FilterIterator(ls.iterator(),
                new Predicate() {
                    public boolean evaluate(String elem) {
                        return elem.length() > 5;
                    }
                });
        while(fi.hasNext()) {
            System.out.println(fi.next());
        }
    }
}

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