N QUEEN PROBLEM: On a NxN board place N queens such that no queen is under attack where a queen can move any steps horizontally, vertically and diagnolly.

public class Nqueen {

      private final int dim = 8;
      private final int queen = 1;
      private int[][] chessBoard  = new int[dim][dim];
      private int count = 0;
      private int startrow = 0;
   
      public void initialize()
      {
            setUpBoard();
            solve(0); 
            System.out.println("\n\nTOTAL NO. OF SOLUTIONS : " + count);
      }
   
 
   /*
         * This function checks whether a queen can be place in cell marked by (row,col)
         * If yes then returns true
         * Else returns false
   */
      public boolean isSafe(int row, int col)
      {
            for(int i=0; i<dim ; i++)
            {
                  if(chessBoard[i][col] == queen && i!= row)
                      return false;
                  if(chessBoard[row][i] == queen && i != col)
                      return false;
            }
         
            //diagnol check
            int i = row-1 , j= col-1;
            while(i>=0 && j>=0)
            {
                  if(chessBoard[i][j] == queen)
                      return false;
                  i--;
                  j--;
            }
         
            i = row+1;
            j=col+1;
            while(i<dim && j<dim)
            {
                  if(chessBoard[i][j] == queen)
                      return false;
                  i++;
                  j++;
            }
         
            i= row-1;
            j = col+1;
            while(i>=0 && j<dim)
            {
            if(chessBoard[i][j] == queen)
           return false;
            i--;
            j++;
            }
         
            i = row+1;
            j = col-1;
            while(i<dim && j>=0)
            {
                  if(chessBoard[i][j] == queen)
                       return false;
                  i++;
                  j--;
            }
            return true;
      }
   
 
   /*
         * This function initialized board to all 0's
   */
      public void setUpBoard()
      {
            for(int i=0; i<dim ; i++)
            {
                  for(int j=0; j<dim ; j++)
                  {
                      chessBoard[i][j] = 0;
                  }
            }
      }
   
 
   /*
         * This function place a queen at row, col position
   */
      public void placeQueen(int row, int col)
      {
            chessBoard[row][col] = queen;
      }
   
 
   /*
         * This function removes a queen placed at row, col position
   */
      public void removeQueen(int row, int col)
      {
            chessBoard[row][col] = 0;
      }
   
 
 
   /*
         * This function displays the chess board.
   */
      public void displayChessBoard()
      {
            for(int i=0 ; i< dim  ; i++)
            {
                  System.out.println();
                  for(int j=0 ; j<dim ; j++)
                  {
                      System.out.print(chessBoard[i][j] + "  ");
                  }
            }
      }
   
   
   /*
         * This function uses backtracking approach and check all possible test cases.
   */
      public void solve(int col)
      {
            if(col >= dim)
            {
                  count++;
                  System.out.println();
                  displayChessBoard();
                  return;
            }
            for(int row =startrow ; row<dim ; row++)
            {
                  if(isSafe(row,col))
                  {
                      placeQueen(row,col);
                      solve(col+1);
                      removeQueen(row,col);
                  }
            }
      }
   
 
      public static void main(String args[])
      {
            Nqueen n = new Nqueen();
            n.initialize();
      }
}