A type system is introduced for a strict but expressive subset of Java in order to infer resource upper bounds on both the heap-space and the stack-space requirements of typed programs. This type system is inspired by previous works on Implicit Computational Complexity, using tiering and non-interference techniques. The presented methodology has several advantages. First, it provides explicit polynomial upper bounds to the programmer, hence avoiding OutOfMemory and StackOverFlow errors. Second, type checking is decidable in linear time. Last, it has a good expressivity since it analyzes most object oriented features like overload, inheritance, override.