Your insertion sort should be more like this:
Code:
public static void insertion_sort()
{
  for( int j = 1; j < accList.length; ++j )
  {
    for( int k = j - 1;
         k >= 0 && accList[j].getAccountNum() < accList[k].getAccountNum();
         --k )
    {
      accList[k+1] = accList[k];
    }
    accList[k + 1] = accList[j];
  }
}
And your deleteAccount function should be more like this:
Code:
public static void deleteAccount( int acc_index )
{
  for( int i = acc_index; i < accList.length - 1; ++i )
  {
    accList[i] = accList[i + 1];
  }
  // Now you must reduce the length of the accList array by one,
  // i.e., the last element must be deleted from the array object.
  // I do not know how that is done in Java.
  // So you need to do what the following line says,
  // but in the Java idiom.
  delete( accList[accList.length - 1] );
}