用java写一个八皇后问题

好的，下面是用 Java 实现八皇后问题的代码：

public class EightQueens {
    private static final int BOARD_SIZE = 8;
    private static int[] queens = new int[BOARD_SIZE];

    public static void main(String[] args) {
        placeQueen(0);
    }

    private static void placeQueen(int row) {
        if (row == BOARD_SIZE) {
            printBoard();
            return;
        }

        for (int col = 0; col < BOARD_SIZE; col++) {
            if (isValidPosition(row, col)) {
                queens[row] = col;
                placeQueen(row + 1);
            }
        }
    }

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

    private static void printBoard() {
        for (int row = 0; row < BOARD_SIZE; row++) {
            for (int col = 0; col < BOARD_SIZE; col++) {
                if (queens[row] == col) {
                    System.out.print("Q ");
                } else {
                    System.out.print(". ");
                }
            }
            System.out.println();
        }
        System.out.println();
    }
}

以上代码运行后会输出所有的八皇后解法。