code: public boolean isSatisfiable(String input) throws SATSolverException {
          Boolean result = solutionsCache.get(input);
          if (null == result) {
              result = satSolver.isSatisfiable(input);
              solutionsCache.put(input, result);
          }
          return result;
      }
docs: Calls the solver and caches the answer.
  
  @param input The String that contains sat problem in DIMACS's format
  @return boolean True if the formula is satisfiable, false otherwise
  @throws SATSolverException SATSolverException