1

我正在为一个将生成和解决数独难题的 java 程序构建 GUI。我这样做的方式是有 1 个主 jpanel，里面有 3x3 jpanel，里面有 3x3 jlabels。

这是我到目前为止所拥有的：

package sudoku;

import java.awt.GridLayout;
import javax.swing.*;
import javax.swing.border.Border;

public class Gui {

    Gui gui;
    JPanel board;
    JPanel subBoard[][];
    GridLayout layout;
    JLabel square[][];
    Border big;
    Border small;

    public void load() {

        gui = new Gui();
        gui.setUp();
        gui.buildBoard();

    }

    private void setUp() {

        layout = new GridLayout(3, 3);
        board = new JPanel(layout);
        subBoard = new JPanel[3][3];
        square = new JLabel[9][9];

    }

    private void buildBoard() {

        // set up board
        board.setVisible(true);

        int mod = 0;
        for (int i = 0; i < 3; i++) {
            for (int j = 0; j < 3; j++) {
                // add subBoards to board
                board.add(subBoard[i][j]);
                subBoard[i][j].setLayout(layout);

                // add textfields to each subBoard
                subBoard[i][j].add(square[i + mod][j + mod]);

            }
            mod += 3;

        }
    }

}

我在这一行收到 NullPointerException 错误：

board.add(subBoard[i][j]);

有人可以解释为什么会这样吗？另外，如果您发现任何其他问题，或者只是我可以这样做的更好方法，请告诉我！谢谢。

4

2 回答 2

4

在你的setUp()方法在这一行

subBoard = new JPanel[3][3];

您只创建了数组，但还没有用 JPanel 填充它。

因此，默认情况下，您的 Array 包含null每个索引位置，因此当您尝试将它们添加到您的board（与subBoard正确初始化为不同的new JPanel(layout)）时，它会引发 NPE。

于 2013-05-20T01:07:28.977 回答
0 
import java.util.Random;
import java.util.Scanner;

public class sudoku {
    public static void main(String[] args) {
        int p = 1;
        Random r = new Random();
        int i1=r.nextInt(8);
        int firstval = i1;
        while (p == 1) {
            int x = firstval, v = 1;
            int a[][] = new int[9][9];
            int b[][] = new int[9][9];
            for (int i = 0; i < 9; i++) {
                for (int j = 0; j < 9; j++) {
                    if ((x + j + v) <= 9)
                        a[i][j] = j + x + v;
                    else
                        a[i][j] = j + x + v - 9;
                    if (a[i][j] == 10)
                        a[i][j] = 1;
                    // System.out.print(a[i][j]+" ");
                }
                x += 3;
                if (x >= 9)
                    x = x - 9;
                // System.out.println();
                if (i == 2) {
                    v = 2;
                    x = firstval;
                }
                if (i == 5) {
                    v = 3;
                    x = firstval;
                }

            }
            int eorh;
            Scanner in = new Scanner(System.in);
            System.out
                    .println("hey lets play a game of sudoku:take down the question and replace the 0's with your digits and complete the game by re entering your answer");
            System.out.println("enter your option 1.hard  2.easy");
            eorh = in.nextInt();
            switch (eorh) {
            case 1:
                b[0][0] = a[0][0];
                b[8][8] = a[8][8];
                b[0][3] = a[0][3];
                b[0][4] = a[0][4];
                b[1][2] = a[1][2];
                b[1][3] = a[1][3];
                b[1][6] = a[1][6];
                b[1][7] = a[1][7];
                b[2][0] = a[2][0];
                b[2][4] = a[2][4];
                b[2][8] = a[2][8];
                b[3][2] = a[3][2];
                b[3][8] = a[3][8];
                b[4][2] = a[4][2];
                b[4][3] = a[4][3];
                b[4][5] = a[4][5];
                b[4][6] = a[4][6];
                b[5][0] = a[5][0];
                b[5][6] = a[5][6];
                b[6][0] = a[6][0];
                b[6][4] = a[6][4];
                b[6][8] = a[6][8];
                b[7][1] = a[7][1];
                b[7][2] = a[7][2];
                b[7][5] = a[7][5];
                b[7][6] = a[7][6];
                b[8][4] = a[8][4];
                b[8][5] = a[8][5];
                b[0][0] = a[0][0];
                b[8][8] = a[8][8];

                break;
            case 2:
                b[0][3] = a[0][3];
                b[0][4] = a[0][4];
                b[1][2] = a[1][2];
                b[1][3] = a[1][3];
                b[1][6] = a[1][6];
                b[1][7] = a[1][7];
                b[1][8] = a[1][8];
                b[2][0] = a[2][0];
                b[2][4] = a[2][4];
                b[2][8] = a[2][8];
                b[3][2] = a[3][2];
                b[3][5] = a[3][5];
                b[3][8] = a[3][8];
                b[4][0] = a[4][0];
                b[4][2] = a[4][2];
                b[4][3] = a[4][3];
                b[4][4] = a[4][4];
                b[4][5] = a[4][5];
                b[4][6] = a[4][6];
                b[5][0] = a[5][0];
                b[5][1] = a[5][1];
                b[5][4] = a[5][4];
                b[5][6] = a[5][6];
                b[6][0] = a[6][0];
                b[6][4] = a[6][4];
                b[6][6] = a[6][6];
                b[6][8] = a[6][8];
                b[7][0] = a[7][0];
                b[7][1] = a[7][1];
                b[7][2] = a[7][2];
                b[7][5] = a[7][5];
                b[7][6] = a[7][6];
                b[8][2] = a[8][2];
                b[8][4] = a[8][4];
                b[8][5] = a[8][5];
                break;
            default:
                System.out.println("entered option is incorrect");
                break;
            }

            for (int y = 0; y < 9; y++) {
                for (int z = 0; z < 9; z++) {
                    System.out.print(b[y][z] + " ");
                }
                System.out.println("");
            }
            System.out.println("enter your answer");
            int c[][] = new int[9][9];
            for (int y = 0; y < 9; y++) {
                for (int z = 0; z < 9; z++) {
                    c[y][z] = in.nextInt();
                }
            }
            for (int y = 0; y < 9; y++) {
                for (int z = 0; z < 9; z++)
                    System.out.print(c[y][z] + " ");
                System.out.println();
            }
            int q = 0;
            for (int y = 0; y < 9; y++) {
                for (int z = 0; z < 9; z++)
                    if (a[y][z] == c[y][z])
                        continue;
                    else {
                        q++;
                        break;
                    }
            }
            if (q == 0)
                System.out
                        .println("the answer you have entered is correct well done");
            else
                System.out.println("oh  wrong answer better luck next time");
            System.out
                    .println("do you want to play a different game of sudoku(1/0)");
            p = in.nextInt();
            firstval=r.nextInt(8);
            /*if (firstval > 8)
                firstval -= 9;*/
        }

    }
}
于 2013-08-05T15:07:35.137 回答