Java 简单计算器程序：使用 UML 类图进行可视化

+----------------------+ | UI | +----------------------+ | -scanner: Scanner | | -calculation:Calculator| +----------------------+ | +main(args: String[])| +----------------------+

+----------------------+ | Calculator | +----------------------+ | +add(a: double, b: double): double| | +subtract(a: double, b: double): double| | +multiply(a: double, b: double): double| | +divide(a: double, b: double): double| +----------------------+

public class UI {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        Calculator calculation = new Calculator();

        System.out.println('请输入两个数值：');
        double num1 = scanner.nextDouble();
        double num2 = scanner.nextDouble();

        System.out.println('请选择要进行的运算符号 (+，-，*，/)：');
        char operator = scanner.next().charAt(0);

        double result = 0.0;
        if (operator == '+') {
            result = calculation.add(num1, num2);
        } else if (operator == '-') {
            result = calculation.subtract(num1, num2);
        } else if (operator == '*') {
            result = calculation.multiply(num1, num2);
        } else if (operator == '/') {
            result = calculation.divide(num1, num2);
        } else {
            System.out.println('输入的运算符号不合法！');
        }

        System.out.println('计算结果：' + result);
    }
}