与J2me读取文件混淆.请帮我理解

Question

我正在为Symbian S60手机的J2ME应用程序工作，从文本文件读取是必需的。我无法访问BufferedReader来从文件中提取一行文本，但我确实在诺基亚帮助论坛中发现了这一点，这让我有点困惑。这是代码，我的问题在下面。谢谢你的回答。

    /**
     * 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。在它的while()循环中，为什么我必须检查readChar != -1和!= 'n' ?我的理解是-1代表流的结束(EOF)。我的理解是，如果我提取一行，我应该只检查换行符。

谢谢。

Answer 1

请仔细阅读代码文档。你所有的疑问都得到了很好的回答。

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，它将返回整个流作为字符串。

Answer 2

这只是你如何(喜欢)将逻辑应用到你试图做/实现的事情。例如，上面的例子可以写成他的

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();
        }
    }

前面的代码示例readChar检查-1只是安全检查