Riemann sum does not return the expected value

I wrote this code to find the sum of Riemann given a function, a range and precision that would be n, but when I execute it it returns "2.0E -8", and then in my calculator this is 6.6666666666666

Could you please help me see what is wrong?

class Suma{
  public static void main (String[]args){

    double x=0;
    double y=Math.pow(x,2)+x+1 ;//función en x
    double a=0;//cota inferior
    double b=2;//cota superior
    double n=100000000;
    double delta=(b-a)/n;//variación de x
    double S=0;//suma
    for(int i=1;i<n+1;i++){
    x=a+i*delta;
    S=+y;   
    }
    S=S*delta;
    System.out.println(S);
    //Scanner i =new Scanner(System.in);
    //n=i.nextInt();

  }
}