java heapify method with comparator

I am trying to write a class HeapQueue. I stored left child of root at 2 * indexOfRoot + 1 index, and right child at 2 * indexOfRoot + 2.

public class HeapQueue implements PriorityQueue, BinaryHeap {

public List<Task> queue;
public Comparator comparator;

public HeapQueue() {
    queue = new ArrayList();
}

public void setComparator(Comparator comparator) {
    this.comparator = comparator;
    heapify(0);
}

public Comparator getComparator() {
    return comparator;
}

public void offer(Task task) {
    int currentElement, previousElement;
    queue.add(task);
    currentElement = queue.size() - 1;
    previousElement = (currentElement - 1) / 2;
    while (previousElement >= 0 && 
             getComparator().compare(queue.get(currentElement), queue.get(previousElement)) > 0) {
        swap(currentElement, previousElement);
        currentElement = previousElement;
        previousElement = (currentElement - 1) / 2;
    }
}

private void swap(int i, int j) {
    Task t1 = queue.get(i);
    Task t2 = queue.get(j);
    Task t3 = t1;
    queue.set(i, t2);
    queue.set(j, t3);
}
}

Queue storaged object of Task.

public class Task {

private final String name;
private final int priority;

public Task(String name, int priority) {
    this.name = name;
    this.priority = priority;
}

public int getPriority() {
    return priority;
}

@Override
public String toString() {
    return name + "\tpriority = " + priority;
}
}

I have a method heapify() in HeapQueue:

public void heapify(int root) {
    int leftChild, rightChild;
    leftChild = 2 * root + 1;
    if (leftChild < queue.size()) {
        rightChild = leftChild + 1;
        if ((rightChild < queue.size())
                && getComparator().compare(queue.get(rightChild), queue.get(leftChild)) > 0) {
            leftChild = rightChild;
        }
        if (getComparator().compare(queue.get(leftChild), queue.get(root)) > 0) {
            swap(root, leftChild);
            heapify(leftChild);
        }
    }

}

By my task comparator may be changed by method setComparator() after adding task to queue. Default Comparator is:

public class Comparator{
    public int compare(Task t1, Task t2) {
        if (t1.getPriority() == t2.getPriority()) {
            return 0;
        } else if (t1.getPriority() < t2.getPriority()) {
            return -1;
        } else {
            return 1;
        } //sorting max
    }
 }

As example other comparator may be:

public class otherComparator{
    public int compare(Task t1, Task t2) {
        if (t1.getPriority() == t2.getPriority()) {
            return 0;
        } else if (t1.getPriority() < t2.getPriority()) {
            return 1;
        } else {
            return -1; 
        } //sorting min
    }
 }

I create my HeapQueue and add some elements.

HeapQueue heap = new HeapQueue();
heap.setComparator(comparator);
Task t1 = new Task("a", 1);
Task t2 = new Task("b", 2);
Task t3 = new Task("c", 3);
Task t4 = new Task("d", 4);
System.out.println(heap.queue.toString());

Result is:

[d priority = 4, c  priority = 3, b priority = 2, a priority = 1]

    4
   / \
  3   2
 /
1 

It's right. But when I change Comparator to otherComparator:

otherComparator newComparator = new otherComparator();
heap.setComparator(newComparator);
System.out.println(heap.queue.toString());

Result is:

[b priority = 2, c  priority = 3, d priority = 4, a priority = 1]

    2
   / \
  3   4
 /
1 

It's wrong. Right answer is something like this:

[a priority = 1, b priority = 2, c  priority = 3, d priority = 4]

    1
   / \
  2   3
 /
4 

I think I have a problem with heapify() function. But I cannot find a mistake. Can someone help?