private boolean wellFormed$()\{$

$//$ Check the invariant.

$//1.$ data is never null

if $($data $==$ null$)$ return report$("$data is nu$11")$; $//$ test the NEGATION of the conditior

$//2.$ The data array is at least as long as the number of items

$//$ claimed by the sequence.

$//$ TODO

$//3.$ currentIndex is never negative and never more than the number of

$//$ items claimed by the sequence.

$//$ TODO

$//$ If no problems discovered, return true

return true;

$\}$

Can help me to complete todo