java为什么这段代码会产生NullPointerException？

Question

我有这个密码：

 public void queryForId(){
    String itemName = textField.getText().substring(7, textField.getText().length());
    String br = System.getProperty("line.separator") + " ";
    try {

        once = false;
        item_found = false;

        BufferedReader bure = new BufferedReader(new FileReader("itemList.txt"));

        while (true) {


            String currentLine = bure.readLine();
            String[] split = currentLine.split(" - ", 2);

            if (split[1].equalsIgnoreCase(itemName)) {

                String id = split[0].replace("\uFEFF", "");// removes the BOM.
                textArea.append(br + "[Innovate] The ID(s) of the item '" + itemName + "' is : " + id + ".");
                textField.setText("");
                item_found = true;

            } else {

                if (!once && !item_found) {
                    textArea.append(br + "[Innovate] The Item cannot be found.");
                    textField.setText("");
                    once = true;
                }
            }

        }


    } catch(IOException z){

        z.printStackTrace();
    }
    }

无论何时使用此方法，我都会得到想要的输出，但它确实会产生nullpointer异常，编译器会指向这一行：

 String[] split = currentLine.split(" - ", 2);

Answer 1

如果要从BufferedReader中获取文本，最好阅读教程并查看示例，因为判断流何时完成的方法是，它是否抛出空值，并且您的代码最好为这种情况做好准备。e、 g

BufferedReader in = ....;
String inputLine = "";

// test for null here when reading in from the Reader
while ((inputLine = in.readLine()) != null) {
    // use inputLine here
}
// close BufferedReader here, usually in a finally block

Answer 2

查看BufferedReader readLine（）方法引用：

Returns: A String containing the contents of the line, not including any line-termination characters, or null if the end of the stream has been reached

因此，当到达输入流中的结尾时，此函数返回null，您将尝试在其上调用split（）方法