Review the API's for
String and
Stack. Each has methods that will be useful, for example String.length() can let you know when you've reached the halfway point. This is what I mean by breaking the problem down...ask specific questions like 1) I need to know where the 'halfway point' in a string is...if I knew the length then I can get half the length (divide by 2)...then how do I get the length of the string? Once I have that, how can I loop over the string? How do I get the character at a specific position? Each of these can be answered using the links above as a reference. Ask one question at a time and build off of each.