java - 数组 "out of bounds"

Question

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我使用 String[3] 数组来存储从 4 个 JTextField 获取的用户输入然后我将数组输出到 txt 文件:

String[] userInfo = new String[3];
    userInfo[0] = sourceTextField.getText();
    userInfo[1] = usernameTextField.getText();
    userInfo[2] = passwordTextField.getText();
    userInfo[3] = emailTextField.getText();
    for (String userInfo1 : userInfo) {
        try 
        {
            BufferedWriter writer = new BufferedWriter(new FileWriter("C:\\Users\\Peace Infinity\\Desktop\\[programming]Projects\\DataFiles\\PasswordRepository.txt", true));
            String s;
            s = userInfo1;
            writer.write(s + " ");
            writer.flush();
        }catch (IOException ex) 
        {
            Logger.getLogger(ADD_dialogBox_v1.class.getName()).log(Level.SEVERE, null, ex);
            JOptionPane.showMessageDialog(null, "Error processing file!");
        }
    }

有人可以告诉我为什么我会收到“数组索引越界”异常吗？谢谢

Answer 1

当您声明一个数组时，您提供该数组的长度/大小。正如您在代码中所做的那样，数组从索引 0 开始，但您正在尝试分配一个值到“越界”索引 - 第四个索引。

new String[3] // index 0,1,2
new String[4] // index 0,1,2,3