MinHeap

public class minheap<Item extends Comparable<Item>> {
    private int size = 0;
    private int capacity;
    private Item[] array;

    @SuppressWarnings("unchecked")
    minheap() {
        this.capacity = 10;
        array = (Item[]) new Comparable[capacity + 1];
    }

    @SuppressWarnings("unchecked")
    minheap(int x) {
        this.capacity = x;
        array = (Item[]) new Comparable[x + 1];
    }

    public void createHeap(Item[] input) {
        if (input.length > 0) {
            for (int i = 0; i < input.length; i++) {
                add(input[i]);
            }
        }
    }

    public void display(){
        for(int i = 1; i < array.length; i++){
            System.out.print(" " + array[i]);
        }
        System.out.println("");
    }

    public void add(Item item) {
        if (size == capacity + 1) {
            if (array[size].compareTo(item) > 0) {
                array[size] = item;
                siftup();
            }
        } else {
            array[++size] = item;
            siftup();
        }
    }

    public void siftup() {
        int i = size;
        while (i > 1 && array[i].compareTo(array[i / 2]) < 0) {
            swap(array, i, i / 2);
            i = i / 2;
        }
    }

    public void swap(Item[] array, int index1, int index2) {
        Item temp = array[index1];
        array[index1] = array[index2];
        array[index2] = temp;
    }

    public void siftdown(int index) {
        int smallest = index;

        while (index <= capacity) {
            if (index * 2  <= size && array[index * 2].compareTo(array[smallest]) < 0) {
                smallest = index * 2;
            }
            if (index * 2 + 1 <= size && array[index * 2 + 1].compareTo(array[smallest]) < 0) {
                smallest = index * 2 + 1;
            }

            if (smallest == index) {
                break;
            }
            swap(array, smallest, index);
            index = smallest;
        }
    }

    public Item extractMin() {
        Item min = getMin();
        swap(array, 1, size);
        array[size--] = null;
        siftdown(1);
        return min;
    }

    public Item getMin() {
        return array[1];
    }

    public void delete(Item item) {
        int i = 1;
        for (i = 1; i <= size; i++) {
            if (array[i] == item) {
                swap(array, i, size);
                array[size--] = null;
                siftdown(i);
                break;
            }
        }
    }

    public int size() {
        return size;
    }

    @SuppressWarnings("unchecked")
    public static void main(String args[]){

        Integer arrA [] = {3,2,1,7,8,4,10,16,12};
        System.out.println("Original Array : ");
        for(int i = 0; i<arrA.length; i++){
            System.out.print("  " + arrA[i]);
        }
        System.out.println();

        @SuppressWarnings("rawtypes")
        minheap heap = new minheap(arrA.length);
        System.out.print("\n Min-Heap : ");
        heap.createHeap(arrA);
        heap.display();

        System.out.print("Extract Min :");
        for(int i=0; i < arrA.length; i++){
            System.out.print("  " + heap.extractMin());
            System.out.print("\n Min-Heap : ");
            heap.display();
        }

    }
}