public class Error
{
    public static void main(String[] args)
    {
        double sum;
        
        sum = listSum(1, 2, 3);    // Call listSum() with 3 arguments
        System.out.println(sum);
        
        sum = listSum(1, 2, 3, 4); // Call listSum() with 4 arguments
        System.out.println(sum);
    }

    public static double listSum( double[] x )
    {
        double s = 0;
        
        for (int i = 0; i < x.length; i++ )
            s = s + x[i];  // Use x like an array...
            
        return s;
    } 
}