每日总结14

5、主程序类：CalculatorApp
import java.util.Scanner;

public class CalculatorApp {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        InputHandler inputHandler = new InputHandler();
        OutputHandler outputHandler = new OutputHandler();

        System.out.println("Enter an expression (e.g., '2 + 3 - 4'): ");
        String input = scanner.nextLine();

        Expression expression = inputHandler.parseExpression(input);
        double result = expression.evaluate();

        outputHandler.printResult(result);
    }
}