Java- n-queens problem

nQueens.java

// The eight queens puzzle is the problem of placing eight chess queens on an 8?8 
// chessboard so that no two queens attack each other. Thus, a solution requires that no two 
// queens share the same row, column, or diagonal. The eight queens puzzle is an example of the more general 
// n-queens problem of placing n queens on an n?n chessboard,
//  where solutions exist for all natural numbers n with the exception of 2 and 3.[
boolean promising (int i, int[] col) {
	for (j=1; j<i; j++) {
		if (col[i] == col[j]) {
			return false;
		} 
		else if (i+col[i] == j + col[j]) {
			return false;
		}
		else if (col[i] - i == col[j] - j) {
			return false;
		}
		
	}
	return true;
}




void nqueens(int i, int n, int[] col)
{
	if (promising(i, col)) {
		if (i == n) {
			printSolution(col);
		}
	}
	for (k=1; k<=n; k++) {
		col[i+1] = k
		nqueens(i+1, n, col)
	}
}