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# Need help for trapezoidal rule java code

## Need help for trapezoidal rule java code

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

<

#### CODE --> Java

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 path name does not exist. Please help. Thanks!

### RE: Need help for trapezoidal rule java code

Hi

Really missing the class declaration line or just a copy-pasting mistake ?

Feherke.
feherke.ga

### RE: Need help for trapezoidal rule java code

(OP)
Copy paste mistake dude. Any thoughts in how to get rid with FileNotFoundException error? Still can't find answers until now...

### RE: Need help for trapezoidal rule java code

Hi

• Are you passing it input file name when running it ?
• If yes, what is that file name ?
• Does the input file ( with the name you pass in parameter or the default InpData.txt ) exist ?

Feherke.
feherke.ga

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