generic array

Hi
I want to implement a generic Heap data structure but I dont know how to create a generic array that fits my need. I need a generic type T which must be a subclass of Comparable. my current approch would generate a ClassCastException. please help me.

import java.util.Random;

public class Heap <T extends Comparable> {
      protected int top;
      protected T arr[];
      protected int capacity;
      
      Heap(int k) {  // List Constructor
            capacity =  k; // Allocate Space
            arr = (T[]) new Object[capacity + 1];
      }

      public static void prt(String s){System.out.print(s);}
      
      // insert x at
      public void insert(T x) {
            arr[++top] = x;
      }
      
      // heap sort
      public void heapSort(){
            int i;
            // heapify from bottom to top
            for ( i = capacity / 2 ; i >= 1 ; i--)
                  heapify(i, capacity);
            for ( i = capacity ; i > 1 ; i--){
                  swap(1, i);
                  heapify(1, i-1);
            }
      }
      
      public void swap(int m, int n) {
            T tmp = arr[m];
            arr[m] = arr[n];
            arr[n] = tmp;
      }
//*******************************************************************
      public void heapify(int m, int k) {
            int minIndex = 2 * m;
            while (minIndex <= k){// m has at least one child
                  if (minIndex + 1 <= k) { // m has 2 children
                        if (arr[minIndex+1].compareTo(arr[minIndex]) > 0)
                        //if (arr[minIndex+1] > arr[minIndex])
                              minIndex ++;
                  }
                  if (arr[minIndex].compareTo(arr[m]) > 0) {
                  //if (arr[minIndex] > arr[m]) {
                        swap(m, minIndex);
                        m = minIndex;
                        minIndex = 2 * m;
                  }
                  else
                        break;
            }
      }
//*******************************************************************
      public String toString() {
            String s  = "[";
            for (int i = 1; i <= top; i++) {
                  s +=  ", " + arr[i] ;
            }
            return s + "]";
      }
//*******************************************************************
      public static void main(String args[]) {
            int p, x, MaxNum = 100;
            Random rand = new Random();
            p = 10;
            // Create List of type Integer
            Heap <Integer> intHeap = new Heap <Integer> (p);
            // Generate data
            for ( int i = 1 ; i <= p ; i++)
                  intHeap.insert(rand.nextInt(MaxNum) + 1);
            
            prt("\nunSorted List: " + intHeap.toString()); // print list
            intHeap.heapSort();
            prt("\n  Sorted List: " + intHeap.toString()+ "\n"); // print list
      }
}