CODEWITHSUNDEEP
javaarraylistreturn
Bipa
Bipa

Reputation: 309

adding returned value into arrayList Java

I am lost in code. I am trying to add a returned value into an ArrayList. The returned value is printed and I have tried to cast it so I can add it to an ArrayList. But nothing seems to be working.

I am in public void getHeap() and like to retrieve the return value from public double remove() to add in an ArrayList. It keeps on telling me source not found. Any help?

Thanks!

public class MinHeap<E extends Comparable<E>> {

    List<E> h = new ArrayList<E>();
    ArrayList<Double> arrayPostingsList = new ArrayList<Double>();

    public void getHeap() {
        MinHeap<Double> heap = new MinHeap<Double>(new Double[]{0.5015530788463572, 0.5962770626486013, 0.4182157748994399});

        ArrayList<Double> newArray = new ArrayList<Double>();
        System.out.println();


        while (!heap.isEmpty()) {
            System.out.println(heap.remove());
            newArray.add(heap.remove());
        }

    }

    public double remove() {
        E removedNode = h.get(0);
        E lastNode = h.remove(h.size() - 1);
        percolateDown(0, lastNode);

        return (Double) removedNode;
    }

    public MinHeap() {
    }

    public MinHeap(E[] keys) {
        for (E key : keys) {
            h.add(key);
        }

        for (int k = h.size() / 2 - 1; k >= 0; k--) {
            percolateDown(k, h.get(k));
        }
    }

    public void add(E node) {
        h.add(null);
        int k = h.size() - 1;
        while (k > 0) {
            int parent = (k - 1) / 2;
            E p = h.get(parent);
            if (node.compareTo(p) >= 0) {
                break;
            }
            h.set(k, p);
            k = parent;
        }
        h.set(k, node);
    }

    public E min() {
        return h.get(0);
    }

    public boolean isEmpty() {
        return h.isEmpty();
    }

    void percolateDown(int k, E node) {
        //....
    }
}

Upvotes: 0

Views: 706

Answers (2)

SimonC
SimonC

Reputation: 6718

You're calling remove() twice:

while (!heap.isEmpty()) {
    System.out.println(heap.remove());
    newArray.add(heap.remove());
}

On the final iteration, when there's only one item left, the second call will fail.

I think your intention is:

while (!heap.isEmpty()) {
    final Double removed = heap.remove();
    System.out.println(removed);
    newArray.add(removed);
}

Upvotes: 0

Jim Garrison
Jim Garrison

Reputation: 86774

Try using this instead:

public E remove() {
    E removedNode = h.get(0);
    E lastNode = h.remove(h.size() - 1);
    percolateDown(0, lastNode);
    return removedNode;
}

Also, I think arrayPostingList should be of type E, not explicitly Double.

Upvotes: 1

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