File 与J2me读取文件混淆。请帮我理解
我正在为Symbian S60手机开发一个J2ME应用程序,需要从文本文件中读取数据。我无法访问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File 与J2me读取文件混淆。请帮我理解,file,text,java-me,File,Text,Java Me,我正在为Symbian S60手机开发一个J2ME应用程序,需要从文本文件中读取数据。我无法访问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 re
/**
* 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()方法的。在它的while()循环中,为什么我必须检查readChar!=-1和!='\不?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,我只需要检查换行符
谢谢。请仔细阅读代码文档。你所有的疑问都在这方面得到了很好的回答
函数正在检查'-1',因为它正在处理没有新行字符的流。在这种情况下,它将以字符串形式返回整个流 请仔细阅读代码文档。你所有的疑问都在这方面得到了很好的回答 函数正在检查'-1',因为它正在处理没有新行字符的流。在这种情况下,它将以字符串形式返回整个流 这正是你(喜欢)将逻辑应用于你试图做/实现的事情的方式。例如,上面的例子可以写得像他的一样
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();
}
}
所以前面的代码示例readChar-1检查只是安全检查。这正是您(喜欢)将逻辑应用于您试图做/实现的事情的方式。例如,上面的例子可以写得像他的一样
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();
}
}
所以前面的代码示例readChar检查-1只是安全检查