Question

start.addActionListener(new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent e) {
            size = Integer.parseInt(sizeText.getText());
            if(size<=1){
                error = "Please key in size more than 1";
                errorMsg.setText(error);
            } else if(size>=5) {
                error = "Please key in size less than 5";
                errorMsg.setText(error);
            } else {

                //create Table 1
                int sizer = size + 1;
                JTable table1 = new JTable(sizer, sizer){
                    public boolean isCellEditable(int r, int c){
                        return false;
                    }
                };
                String[][] Object = new String[sizer][sizer];
                String[][] Object2 = new String[sizer][sizer];
                int i = 1;
                Object[0][0] = " ";
                for(int r = 1; r<sizer; r++){
                    String text1 = "Col " + r;
                    table1.setValueAt(text1, r, 0);
                    for(int c = 1; c<sizer; c++){
                        String text2 = "Row " + c;
                        table1.setValueAt(text2, 0, c); 
                    }//first loop
                }//second loop
                for(int r = 1; r<Object.length; r++){
                    for(int c = 1; c<Object.length; c++){
                        Object2[r][c] = String.valueOf(i);
                        i++;
                        System.out.print(Object2[r][c]);
                        table1.setValueAt(Object2[r][c], r, c);
                    }
                    System.out.println();
                }

                for(int r = 1; r<Object2.length; r++){
                    for(int c = 1; c<Object2.length; c++){
                        int rnd = new Random().nextInt(size);
                        String temp = Object2[r][c];
                        System.out.println("1: "+temp+ "/" +Object2[r][c]);
                        Object2[r][c] = Object2[rnd][c];
                        System.out.println("2: "+Object2[r][c]+ "/" +Object2[rnd][c]);
                        Object2[rnd][c] = temp;     
                        System.out.println("3: "+Object2[rnd][c]+ "/" + temp);
                    }//first loop
                }//second loop

                for(int r = 1; r<Object.length; r++){
                    for(int c = 1; c<Object.length; c++){   
                        table1.setValueAt(Object2[r][c], r, c);
                        panel2.add(table1);

                    }//first loop
                }//second loop  

                start.setEnabled(false);
                start.setText("Good Luck!");
                errorMsg.setVisible(false);
            }}  
    });

我打印系统的原因是我要检查洗牌过程。事实证明，由于没有明显的原因，它的值为空值。我一直想弄清楚。我的JTable将有空格

Answer 1

使用

初始化后

for(int r = 1; r<Object.length; r++){
    for(int c = 1; c<Object.length; c++){
        Object2[r][c] = String.valueOf(i);
        i++;
        System.out.print(Object2[r][c]);
        table1.setValueAt(Object2[r][c], r, c);
    }
    System.out.println();
}

数组包含以下内容（.字段为null）

       0  1  2  3  4
    0  .  .  .  .  .
    1  .  1  2  3  4 
    2  .  5  6  7  8
    3  .  9 10 11 12
    4  . 13 14 15 16

它因为数组使用基于零的索引。

稍后当你洗牌时

int rnd = new Random().nextInt(size)

rnd的值在以下范围0 <= rnd < size。这意味着可以使用某些字符串值交换null值。

做洗牌时是空的

1 个答案: