대규모 코드 베이스에서 함수를 모듈화하고 재사용하기 위한 모범 사례

// 计算圆的面积
public double calcCircleArea(double radius) {
    return Math.PI * radius * radius;
}

// 计算矩形的面积
public double calcRectangleArea(double width, double height) {
    return width * height;
}

// 定义一个计算面积的通用函数
public double calcArea(Shape shape) {
    return switch (shape.getType()) {
        case CIRCLE -> Math.PI * shape.getRadius() * shape.getRadius();
        case RECTANGLE -> shape.getWidth() * shape.getHeight();
        default -> throw new IllegalArgumentException("Unknown shape type");
    };
}

// Shape 接口定义了形状类型的常量
public interface Shape {
    enum Type {
        CIRCLE,
        RECTANGLE
    }

    Type getType();

    double getRadius();

    double getWidth();

    double getHeight();
}

// Circle 和 Rectangle 类实现 Shape 接口
public class Circle implements Shape {
    private double radius;

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

    @Override
    public Type getType() {
        return Type.CIRCLE;
    }

    @Override
    public double getRadius() {
        return radius;
    }
}

public class Rectangle implements Shape {
    private double width;
    private double height;

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

    @Override
    public Type getType() {
        return Type.RECTANGLE;
    }

    @Override
    public double getWidth() {
        return width;
    }

    @Override
    public double getHeight() {
        return height;
    }
}