割圆法求圆周率

public class Yuan {

    public static void main(String[] args) {
        circular cObj = new circular();
        cObj.setRadius(1);
        double pi = cObj.pi(100);
        System.out.println(pi); // 输出 3.1415926535897936

        // 也可以通过求面积方式求pi 
        // double area = cObj.area(1, 1000000000);
        // System.out.println(area); // 输出 3.141592659677579 精度上差了一些
    }
}

class circular {
    private double radius;
    private double perimeter;

    public void setRadius(double radius) {
        this.radius = radius;
    }
    public double getRadius() {
        return this.radius;
    }

    public double getPerimeter() {
        return this.perimeter;
    }

    public double newSide(double sideLen){
        double sas = this.radius - Math.sqrt((this.radius*this.radius-sideLen*sideLen/4));
        return Math.sqrt(sas*sas+sideLen*sideLen/4);
    }

    public double pi(int m){
        double n = 6;
        double sideLen = 0;
        double r = this.radius;
        this.perimeter = 2*this.radius;
        for (int i=1; i<=m; i++) {
            sideLen = this.newSide(r);
            r = sideLen;
            n *=2;
        }
        this.perimeter=sideLen*n;
        return this.perimeter/(2*this.radius);
    }

    public double area(double r, int cutNum){
        double area =0;
        double y=r;
        double unitLen = r/cutNum;
        double x=unitLen;
        while(y>0){
            if((x*x+y*y)<r*r){
                area+=unitLen*y;
                x+=unitLen;
            }else{
                y-=unitLen;
            }
        }
        return area*4;
    }
}