tabulasi

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package tabulasi;
import java.util.Scanner;
import java.math.*;
/**
 *
 * @author surya
 */
public class Tabulasi {
private static float x1,x2,x,xa,xb,h,y,y1,y2,ya,yb;
private static int i,j,k;
private static String tampung,x1k,x2k;
    /**
     * @param args the command line arguments
     */

    public static void main(String[] args) {
        // TODO code application logic here
        Scanner datain = new Scanner (System.in);
        do{
        System.out.print("Masukkan batas atas = ");
        x1 = datain.nextInt();
        y1 = x1*x1*x1-7*x1+1;
        System.out.print("Masukkan batas bawah = ");
        x2 = datain.nextInt();
        y2 = x2*x2*x2-7*x2+1;
        }while ((y1*y2)>=0);
        k=0;
        do {
            k= k+1;
            if(x1>x2){
                xa=x1;
                xb=x2;
            }else{
                xa=x2;
                xb=x1;
            }
            h=(xa-xb)/10;
            i=0;
            do{
                i=i+1;
                x=xb+h*i;
                ya=x*x*x+7*x-1;
                yb=(x-h)*(x-h)*(x-h)-7*(x-h)+1;
            }while ((ya*yb)>0);
            x1=x;
            x2=x-h;
            tampung="Tabulasi ke-"+k+"\n";
            tampung+="----------------------------------------"+"\n";
            tampung+="n         x          f(x)       error   "+"\n";
            tampung+="----------------------------------------"+"\n";
            while (j<=9){
               x = xb + h * (j - 1);
               y = x * x * x - 7 * x + 1;
               tampung+=""+j+" :: "+x+"   ::  "+y+"  ::  "+Math.abs(y)+"  ::  "+"\n";
               j++;
            }
            j=10;
            while(j<=11){
               x = xb + h * (j - 1);
               y = x * x * x - 7 * x + 1;
               tampung+=""+j+" :: "+x+"  ::  "+y+"  ::  "+Math.abs(y)+"  ::  "+"\n";
               j++;
            }
            tampung+="-------------------------------------------";
        } while (Math.abs((y))<10e-8);
        tampung+="Akar pendekatan = "+x+"\n";
        tampung+="Error = "+Math.abs(y)+"\n";
        System.out.print(tampung);
    }

}