Question

我正在为Symbian S60手机开发J2ME应用程序，需要从文本文件中读取。我没有访问BufferedReader从文件中提取一行文本，但我确实在诺基亚帮助论坛中找到了这个，它让我有点困惑。这是代码，我的问题如下。谢谢回答。


    /**
     * Reads a single line using the specified reader.
     * @throws java.io.IOException if an exception occurs when reading the
     * line
     */
    private String readLine(InputStreamReader reader) throws IOException {
        // Test whether the end of file has been reached. If so, return null.
        int readChar = reader.read();
        if (readChar == -1) {
            return null;
        }
        StringBuffer string = new StringBuffer("");
        // Read until end of file or new line
        while (readChar != -1  && readChar != '\n') {
            // Append the read character to the string. Some operating systems
            // such as Microsoft Windows prepend newline character ('\n') with
            // carriage return ('\r'). This is part of the newline character
            // and therefore an exception that should not be appended to the
            // string.
            string.append((char)readChar);

            // Read the next character
            readChar = reader.read();
        }
        return string.toString();
    }

我的问题是关于readLine（）方法。在while（）循环中，为什么我必须检查readChar！= -1和！='\ n'？据我所知，-1表示流的结束（EOF）。我的理解是，如果我提取一行，我只需要检查换行符。

感谢。

Answer 1

请仔细阅读代码文档。你所有的疑惑都得到了很好的回答。

该函数正在检查'-1'，因为它正在处理那些没有新行字符的流。在这种情况下，它将整个流作为字符串返回。

Answer 2

这就是你（如何）将逻辑应用于你尝试做/实现的方式。例如，上面的例子可能就像他的

一样


private String readLine(InputStreamReader reader) throws IOException {
        // Test whether the end of file has been reached. If so, return null.
        int readChar = reader.read();
        if (readChar == -1) {
            return null;
        }else{
            StringBuffer string = new StringBuffer("");

            // Read until end of file or new line
            while (readChar != '\n') {
                // Append the read character to the string. Some operating systems
                // such as Microsoft Windows prepend newline character ('\n') with
                // carriage return ('\r'). This is part of the newline character
                // and therefore an exception that should not be appended to the
                // string.
                string.append((char)readChar);

                // Read the next character
                readChar = reader.read();
            }
            return string.toString();
        }
    }

以前的代码示例readChar检查-1只是安全检查。

与J2me阅读文件混淆。请帮我理解

2 个答案: