【数学计算】圆周率

public static double getPi(){
        double sum=2;
        int n=1;
        int m=3;
        double t=2;
        // 1e-15 precision
        while(t>1e-15){
            t=t*n/m;
            sum=sum+t;
            n++;
            m+=2;
        }
        return sum;
    }