Java for循环逻辑问题

Question

我无法理解为什么我的for循环没有按照我的意愿行事.我的循环的目的是将多个文本字段添加到GUI,准确地说是70.7横穿,10横.它添加了很好的字段,但是停止了比我想要的更短的一行和一列.这似乎足以确定问题的信息,但我不能,所以我来到这里.

        for(int i = 0; i < 6; i++){
            for(int j = 0; j < 9; j++){
                OT2Field[i][j] = new JTextField();
                OT1Field[i][j] = new JTextField();
                STField[i][j] = new JTextField();
            }
        }

        int xPointer = 3;
        int yPointer = 7;
        for(int i = 0; i < 6; i++){
            for(int j = 0; j < 9; j++){
                addTimeFieldBorder0010(option3, OT2Field[i][j], gridbag, gbc, xPointer, yPointer, 1, 1, 0);
                yPointer = yPointer + 3;
            }
            xPointer++;
            yPointer = 7;
        }


    }

    private void addTimeFieldBorder0010(JComponent container, JComponent component, 
            GridBagLayout gridbag, GridBagConstraints gbc,
            int x, int y, int height, int width, double weightx) {
        gbc.gridx = x;
        gbc.gridy = y;
        gbc.gridheight = height;
        gbc.gridwidth = width;
        gbc.weightx = weightx;
        ((JTextField) component).setHorizontalAlignment(JLabel.CENTER);
        component.setBorder(BorderFactory.createMatteBorder(0, 0, 1, 0, Color.red));
        component.setFont(component.getFont().deriveFont(18.0f));
        component.setForeground(Color.red);
        component.setBackground(Color.YELLOW);
        gridbag.setConstraints(component, gbc);


        container.add(component, gbc);
     }

Answer 1

根据Java语言规范§15.20.1,

• 如果左侧操作数的值小于右侧操作数的值,则<运算符产生true的值为,否则为false.

所以,你开始i = 0和循环,同时i是少比6.您需要循环,当它小于7,或小于或等于6.这同样适用于你的下一个循环.

将您的两个循环更改为:

for(int i = 0; i < 7; i++){
    for(int j = 0; j < 10; j++){
        //stuff
    }
}

Answer 2

外部循环仅从0到5执行,内部循环仅从0到8执行.将循环更改为

for(int i = 0; i < 7; i++){
        for(int j = 0; j < 10; j++){
            OT2Field[i][j] = new JTextField();
            OT1Field[i][j] = new JTextField();
            STField[i][j] = new JTextField();
        }
    }

该<符号返回false时,左边的值等于正确.因此i=6,i<6返回false,因此您缺少一次迭代.

Answer 3

你在0 to 5for循环i和0 to 8for 循环之间循环j.这就是它停止一行一列的原因.你应该改变它们如下:

for(int i = 0; i <= 6; i++){
  for(int j = 0; j <= 9; j++){
    ...
  }
}

要么

for(int i = 0; i < 7; i++){
  for(int j = 0; j < 10; j++){
    ...
  }
}