/* From: "COMPUTATIONAL PHYSICS, 2nd Ed" 
   by RH Landau, MJ Paez, and CC Bordeianu 
   Copyright Wiley-VCH, 2007.
   Electronic Materials copyright: R Landau, Oregon State Univ, 2007;
   MJ Paez, Univ Antioquia, 2007; and CC Bordeianu, Univ Bucharest, 2007.
   Support by National Science Foundation                              
*/
/* LaplaceLine.java: Laplace eqn via finite difference mthd 
                      wire in grounded box, Output for 3D gnuplot */
											
import java.io.*; 

public class LaplaceLine  {
  static int  Nmax = 100;                              // Size of box
  
  public static void main(String[] argv) 
                         throws IOException, FileNotFoundException {
													 
    double V[][] = new double[Nmax][Nmax]; 
    int i, j, iter; 
		
    PrintWriter w =   new PrintWriter            // Save data in file
                     (new FileOutputStream("LaplaceLine.dat"), true);
				                                               // Initialize
    for (i=0;  i<Nmax;  i++)                           
       { for (j=0;  j<Nmax;  j++) V[i][j] = 0.; }
    for ( i=0;  i < Nmax;  i++ ) V[i][0] = 100. ;  // V(wire) = 100 V
		                                                    // Iterations
    for ( iter=0;  iter < 1000;   iter++ ) {   
			                                        // x, then y directions
      for ( i=1;  i < (Nmax-1);  i++ )  {                     
        for ( j=1;  j < (Nmax-1);  j++ )                      
				                                              // THE ALGORITM  
           V[i][j] = (V[i+1][j]+V[i-1][j]+V[i][j+1]+V[i][j-1])/4.;  
      }
    }
    for ( i=0;  i < Nmax ;  i=i + 2)  {     // Data in gnuplot format
      for ( j=0;  j < Nmax;  j=j + 2) w.println("" + V[i][j] + ""); 
      w.println("");                     // Blank line separates rows
    }                             
    System.out.println("data stored in LaplaceLine.dat"); 
  }                                                       // End main
}                                                        // End class