Java中利用Scanner和条件判断实现用户自定义形状面积计算

// Rectangle类
class Rectangle {
    private double height;
    private double width;

    // 构造函数，用于初始化矩形的长和宽
    public Rectangle(double height, double width) {
        this.height = height;
        this.width = width;
    }

    // 计算矩形面积的方法
    public double calculateArea() {
        return height * width;
    }
}

// Circle类
class Circle {
    private double radius;

    // 构造函数，用于初始化圆形的半径
    public Circle(double radius) {
        this.radius = radius;
    }

    // 计算圆形面积的方法
    public double calculateArea() {
        // 使用Math.PI提供更精确的圆周率
        return radius * radius * Math.PI;
    }
}

import java.util.InputMismatchException;
import java.util.Scanner;

public class ShapeAreaCalculator {
    public static void main(String[] args) {
        Scanner keyboard = new Scanner(System.in);
        System.out.println("请输入您想计算面积的形状 (rectangle, circle): ");
        String shapeChoice = keyboard.nextLine().toLowerCase(); // 读取形状名称并转换为小写，方便比较

        double area = 0; // 初始化面积变量

        // 根据用户输入的形状选择执行不同的逻辑
        if ("rectangle".equals(shapeChoice)) {
            // ... 处理矩形输入和计算
        } else if ("circle".equals(shapeChoice)) {
            // ... 处理圆形输入和计算
        } else {
            System.out.println("未知形状。目前支持 'rectangle' 和 'circle'。");
        }

        keyboard.close(); // 关闭Scanner，释放资源
    }
}

import java.util.InputMismatchException;
import java.util.Scanner;

// Rectangle类 (同上)
class Rectangle {
    private double height;
    private double width;

    public Rectangle(double height, double width) {
        this.height = height;
        this.width = width;
    }

    public double calculateArea() {
        return height * width;
    }
}

// Circle类 (同上)
class Circle {
    private double radius;

    public Circle(double radius) {
        this.radius = radius;
    }

    public double calculateArea() {
        return radius * radius * Math.PI;
    }
}

public class ShapeAreaCalculator {
    public static void main(String[] args) {
        Scanner keyboard = new Scanner(System.in);
        double area = 0; // 初始化面积变量

        try {
            System.out.println("请输入您想计算面积的形状 (rectangle, circle): ");
            String shapeChoice = keyboard.nextLine().toLowerCase(); // 读取形状名称并转换为小写

            if ("rectangle".equals(shapeChoice)) {
                System.out.println("请输入矩形的长度: ");
                double length = keyboard.nextDouble();
                System.out.println("请输入矩形的宽度: ");
                double width = keyboard.nextDouble();

                if (length <= 0 || width <= 0) {
                    System.out.println("长度和宽度必须为正数。");
                } else {
                    Rectangle rect = new Rectangle(length, width);
                    area = rect.calculateArea();
                    System.out.println("矩形的面积是: " + area);
                }

            } else if ("circle".equals(shapeChoice)) {
                System.out.println("请输入圆形的半径: ");
                double radius = keyboard.nextDouble();

                if (radius <= 0) {
                    System.out.println("半径必须为正数。");
                } else {
                    Circle circle = new Circle(radius);
                    area = circle.calculateArea();
                    System.out.println("圆形的面积是: " + area);
                }

            } else {
                System.out.println("未知形状。目前支持 'rectangle' 和 'circle'。");
            }
        } catch (InputMismatchException e) {
            System.out.println("输入无效。请确保输入的是数字。");
        } finally {
            keyboard.close(); // 确保Scanner在任何情况下都被关闭
        }
    }
}