n皇后问题java递归

好的，关于n皇后问题的Java递归实现，可以参考以下代码：

public class NQueens {
    private int[] queens;
    private int n;

    public void solve(int n) {
        this.n = n;
        queens = new int[n];
        placeQueen(0);
    }

    private void placeQueen(int row) {
        if (row == n) {
            printQueens();
            return;
        }
        for (int col = 0; col < n; col++) {
            if (isValid(row, col)) {
                queens[row] = col;
                placeQueen(row + 1);
            }
        }
    }

    private boolean isValid(int row, int col) {
        for (int i = 0; i < row; i++) {
            if (queens[i] == col || Math.abs(queens[i] - col) == row - i) {
                return false;
            }
        }
        return true;
    }

    private void printQueens() {
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < n; j++) {
                if (queens[i] == j) {
                    System.out.print("Q ");
                } else {
                    System.out.print(". ");
                }
            }
            System.out.println();
        }
        System.out.println();
    }
}