java设计并实现符合单一职责原则、里氏替换原则、组合复用原则的计算器演示系统代码

非常感谢您对设计模式的关注！以下是一个实现了单一职责、里氏替换、组合复用原则的计算器演示系统代码示例：

import java.util.Scanner;

interface Operation {
    double getResult(double num1, double num2);
}

class Add implements Operation {
    @Override
    public double getResult(double num1, double num2) {
        return num1 + num2;
    }
}

class Subtract implements Operation {
    @Override
    public double getResult(double num1, double num2) {
        return num1 - num2;
    }
}

class Multiply implements Operation {
    @Override
    public double getResult(double num1, double num2) {
        return num1 * num2;
    }
}

class Divide implements Operation {
    @Override
    public double getResult(double num1, double num2) {
        return num1 / num2;
    }
}

class Calculator {
    private Operation operation;
    public void setOperation(Operation operation) {
        this.operation = operation;
    }
    public double getResult(double num1, double num2) {
        return operation.getResult(num1, num2);
    }
}

public class Demo {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        double num1, num2;
        System.out.println("Please enter two numbers:");
        num1 = scanner.nextDouble();
        num2 = scanner.nextDouble();

        Calculator calculator = new Calculator();

        System.out.println("Please select the operation you want to perform:");
        System.out.println("1. Add");
        System.out.println("2. Subtract");
        System.out.println("3. Multiply");
        System.out.println("4. Divide");

        int choice = scanner.nextInt();

        switch (choice) {
            case 1:
                calculator.setOperation(new Add());
                break;
            case 2:
                calculator.setOperation(new Subtract());
                break;
            case 3:
                calculator.setOperation(new Multiply());
                break;
            case 4:
                calculator.setOperation(new Divide());
                break;
            default:
                System.out.println("Invalid choice!");
                return;
        }

        double result = calculator.getResult(num1, num2);
        System.out.println("Result: " + result);
    }
}

希望代码能够帮助您理解设计模式的实际应用。还有什么问题可以随时向我提出哦！