Find Kth smallest in a given integer array java

public int findksmallest(int[] array, int k) throws Exception {
  if (k <= array.length && k > 0) { 
   for( int i =0 ; i < k ;i++){
          for ( int j = i+1 ; j< array.length ; j++){
              if(array[j] < array[i]){
               int tmp = array[i];
               array[i] = array[j];
               array[j] = tmp;
              }
          }
   }
  }else{
   throw new Exception("k is an invalid number");
  }
  return array[k-1];
 }