Java boolean 值未从 if 语句中传递出去

Question

我是 Java 的新手，无法弄清楚为什么我的 if 语句中的 boolean 值不能传递到 System.out.println(aa + ""+ bb + ""+ gate); 下面。目标是在 if 语句中设置 boolean 值 aa 和 bb ，然后将这两个变量传递给另一个方法 calculate(aa , bb);.正确的值从每个 if 语句返回，但不是从 System.out.println(aa + ""+ bb + ""+ gate);。如何保存两个 boolean 值并将它们传递给其他东西？

 JButton btnCalculate = new JButton("Calculate");
    btnCalculate.addActionListener(new ActionListener() {
        JFrame error = new JFrame();
        public void actionPerformed(ActionEvent arg0) {
         try {
            int a = Integer.parseInt(textInputA.getText());
            int b = Integer.parseInt(textInputB.getText());
            String gate = String.valueOf(comboBoxGateSelect.getSelectedItem());
            if(a == 1) {
                boolean aa = true;
                System.out.println("a is " + aa + "(1)");
            }
            if(a == 0) {
                boolean aa = false;
                System.out.println("a is " + aa + "(0)");
            }
            if(b == 1) {
                boolean bb = true;
                System.out.println("b is " + bb + "(1)");
            }
            if(b == 0) {
                boolean bb = false;
                System.out.println("b is " + bb + "(0)");
            }
            if(a > 1 || a < 0) {
                JOptionPane.showMessageDialog(error, "Input A must be either 1 or 0. \r\n True = 1, False = 0.", "Error", JOptionPane.ERROR_MESSAGE, null);
            }
            if(b > 1 || b < 0) {
                JOptionPane.showMessageDialog(error, "Input B must be either 1 or 0. \r\n True = 1, False = 0.", "Error", JOptionPane.ERROR_MESSAGE, null);
            }
            System.out.println(a + " " + b + " " + gate);
            System.out.println(aa + " " + bb + " " + gate); // This one +
            calculate(aa, bb); // This one.
         } catch(NumberFormatException e) {
             JOptionPane.showMessageDialog(error, "Inputs A and B must be either 1 or 0. \r\n True = 1, False = 0.", "Error", JOptionPane.ERROR_MESSAGE, null);
         }      

        }
    });
    btnCalculate.setBackground(Color.GRAY);
    btnCalculate.setFont(new Font("Arial", Font.BOLD, 11));
    btnCalculate.setForeground(Color.BLACK);
    btnCalculate.setBounds(72, 204, 89, 23);
    contentPane.add(btnCalculate);

Answer 1

在 if 语句、循环或任何带有括号 {} 的内容中声明的变量，仅可以在这些括号内访问。要在 if 语句之外访问变量，请像这样声明它:

boolean aa;    
if(a == 1) {     
aa = true;           
   System.out.println("a is " + aa + "(1)");
}