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Passing arrays in java

Here is my code which calculates some values. I have problem with passing arrays to function and constructor. can any one fix it.
code..........
import java.io.*;
public class correlate
{
      double x[];
      double y[];

      public correlate (double a[],double b[],int n)
      {
            for (int i=0;i<n;i++)
                  {
                        x[i]=a[i];
                        y[i]=b[i];
                  }
      }
      public double SumOfProduct_X_Y();
      {
            double sumofproduct_x_y =0;
            for (int i=0;i<n;i++)
                  {
                   sumofproduct_x_y = sumofproduct + ( x[i] * y[i]);
                  }

            return (n * sumofproduct_x_y );
      }

      public double ProductOfSum_X_Y();
      {
            double sum_x = 0, sum_y =0, productofsum_x_y = 0;
            for (int i=0;i<n;i++)
                  {
                   sum_x = sum_x + x[i];
                   sum_y = sum_y + y[i];
                  }

            productofsum_x_y = (sum_x * sum_y);
            return productofsum_x_y;
      }

      public double SumOf_X_Squares();
      {
            double sumof_x_squares = 0;
            for (int i=0;i<n;i++)
                  {
                  sumof_x_squares = sumof_x_squares + (x[i]*x[i]) ;
                  }
            return (n * sumof_x_squares);
      }
      public double SumOf_Y_Squares();
      {
            double sumof_y_squares = 0;
                  for (int i=0;i<n;i++)
                  {
                  sumof_y_squares = sumof_y_squares + (y[i]*y[i]) ;
                  }

            return (n * sumof_y_squares);
      }
      public double SquareOf_Sum_X();
      {
            double squareof_sum_x = 0;
            for (int i=0;i<n;i++)
                        {
                        squareof_sum_x = squareof_sum_x + (x[i]) ;
                        }
                  return squareof_sum_x;
      }
      public double SquareOf_Sum_Y();
{
                  double squareof_sum_y = 0;
                  for (int i=0;i<n;i++)
                              {
                              squareof_sum_y = squareof_sum_y + (y[i]) ;
                              }
                  return squareof_sum_y;

      }

      public static void main(String args[])
      {
            double A,B,C,D,E,F;
            correlate c1 = new correlate();
            double a[] = { 12, 13, 14, 15};
            double b[] = { 23, 24, 25, 26};

            c1(a[],b[]);

            A = c1.SumOfProduct_X_Y();
            B = c1.ProductOfSum_X_Y();
            C = c1.SumOf_X_Squares();
            D = c1.SquareOf_Sum_X()
            E = c1.SumOf_Y_Squares();
            F = c1.SquareOf_Sum_Y()
            System.out.println(" ",A+B+C+D+E+F);
      }

}

aozarov

c1(a[],b[]) -> c1(a,b);

ASKER CERTIFIED SOLUTION

CEHJ

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zzynx

CEHJ is right. This is why:

public class correlate
{
double x[]; // <<< Here you only define x as being a (yet undefined) reference to a double array (x = null)
double y[]; // <<< Here you only define x as being a (yet undefined) reference to a double array (y = null)

Before you start using x and y you'll have to specify what they reference:

public correlate (double a[],double b[],int n) {
x = new double[n]; // <<<< Here you (1) create a new double array of length n in memory and (2) let x reference it
y = new double[n]; // <<<< Here you (1) create a new double array of length n in memory and (2) let y reference it
// From now on, you can safely use x and y (since they are no longer null)
for (int i=0;i<n;i++) {
x[i]=a[i];
y[i]=b[i];
}
}

CEHJ

:-)