CPE208-Runge Kutta's Method

public class Runge {
    public static void main(String[] args){
        double a,b,x,y;
        double h;
        int[] n = new int[]{10, 20, 50, 100, 200, 500, 1000};
        a = 0;
        x = b = 1;
        y = x;

        for(int i = 0 ; i < n.length ; i++){
            double k1,k2,k3,k4;
            h = (b-a)/n[i];
            for(int j = 0 ; j < n[i] ; j++){
                k1=y;
                k2=y+((h*k1)/2);
                k3=y+((h*k2)/2);
                k4=y+(h*k3);
                y=y+((h/6)*(k1+(2*k2)+(2*k3)+k4));
            }
            if(i < 3)
                System.out.println("n = "+ n[i] +";\t\t"+y+"\terror = "+(Math.E-y)+"\tlog|error| = "+ Math.log10(Math.E-y));
            else
                System.out.println("n = "+ n[i] +";\t"+y+"\terror = "+(Math.E-y)+"\tlog|error| = "+ Math.log10(Math.E-y));
            y = x;
        }
    }
}