Doubt in the code

#1

what exactly are we doing from line 3rd to 10th and why .
private DynamicStack -what this line do
please clearify what are these lines exactly doing

#2

@Adhyayan we are declaring the dynamic stack and making it primary and secondary.
we need a constructor to initialise these stacks so that e can go ahead with creating queue so the line 7-10 are that .

#3

Here dynamic stack means the stack which we have already created in separate class extending stack ???

#4

@Adhyayan yeah we have already created them