String manipulations gogo

alright, so I'm retarded when it comes to c++

I want an if condition of if the current part of a string is a bracket or a paren.

how the fuck I do that?

if (input.whatthefuckgoeshere == "[";)

I take a user input, in general a string of something like "[3+4]+1"

I want to count the matching parens.

so I know I'm going to need someting like:

if (input.whatevergoeshere == "(")

the only java equivalent I know of is input.charAt()