Write a java method that will take two sorted stacks A and B (min on top), and return one
stack D that is sorted (min on top). You are allowed to use only the stack operations such as
pop, push, isEmpty and peek.
Example: suppose A={(top)1,4,7,9} and B={(top)2,3,6}, then the function will return a new
stack D= {(top) 1,2,3,4,6,7,9}