StringCalculator.java

package calculator;

public class StringCalculator {

    public static void main(String[] args) {

        StringCalcScanner scanner = new StringCalcScanner();

        while (true) {
            System.out.println("Please, enter Your choice '1'(read from file) or '2'(manual input) or '3' to exit: ");
            String choice = scanner.scanString();

            if (choice.equals("1")) {
                String line;
                line = StringFileReader.FileReader();
                StringDoubleCalculating.precondition(line);

            } else if (choice.equals("2")) {
                System.out.println("Please, enter the whole operation(x +-*/ y) ");
                String scanLine = scanner.scanString();
                StringDoubleCalculating.precondition(scanLine);

            }else if (choice.equals("3")) {
               break;

            } else {
                continue;
            }
        }
    }

}