Java计算圆面积代码教学

public class CircleArea {
    public static void main(String[] args) {
        double radius = 5.0; // 圆的半径
        double area = Math.PI * radius * radius; // 使用 Math.PI 和面积公式
        System.out.println("圆的面积为: " + area);
    }
}

import java.util.Scanner;

public class CircleArea {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        System.out.print("请输入圆的半径: ");
        double radius = input.nextDouble();
        double area = Math.PI radius radius;
        System.out.println("圆的面积为: " + area);
        input.close();
    }
}

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

    public static void main(String[] args) {
        double radius = 4.5;
        double area = calculateArea(radius);
        System.out.println("半径为 " + radius + " 的圆面积是: " + area);
    }
}