Need help on Trapezoidal Rule Java code

Question

Need help... I tried running the code for trapezoidal rule. It's my project in Numerical Methods, here's the code:

static double trapezoidRule (int size, double[] x, double[] y)
   {  double sum = 0.0,
             increment;

      for ( int k = 1; k < size; k++ )
      {//Trapezoid rule:  1/2 h * (f0 + f1)
         increment = 0.5 * (x[k]-x[k-1]) * (y[k]+y[k-1]);
         sum += increment;
      }
      return sum;
   }

   public static void main ( String[] args ) throws Exception
   {  String   fileName = args.length > 0 ? args[0] : "InpData.txt";
      Scanner  inp = new Scanner(new File(fileName));
      int      k, size;
      double[] x, y;
      double   integral;

      size = inp.nextInt();
      System.out.println ("Number of points:  " + size);

      x = new double[size];
      y = new double[size];

      for ( k = 0; k < size; k++ )
      {  x[k] = inp.nextDouble();
         y[k] = inp.nextDouble();
      }
      integral = trapezoidRule (size, x, y);
      System.out.printf ("Integral:  %4.4f\n", integral);
      System.out.printf ("Check:  log(%2.2f) = %8.8f\n",
                         x[size-1], Math.log(x[size-1]) );
   }
}

It cannot be compiled and I always get FileNotFoundException. I found on Javadocs that this will be thrown when a file with the pathname does not exist. Please help. Thanks!

Answer 1

Probably InpData.txt is not in your working directory. The simplest solution: try to put full path to the file, not just the name. Eg: "C:\\\\somefiles\\\\...\\\\InpData.txt"

Answer 2

Where is the file InpData.txt?

Place a breakpoint and debug new File(fileName).getAbsolutePath() to see where it should be. Place your file there.

Don't hard-code the path if you want the code to be portable (if it is being executed on another machine).

Answer 3

It is runtime error - your file "InpData.txt" may not be in your working directory. Try to put full path or move file to your working directory.