java 在java中，一次读入一个字符时，如何确定EOF？
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In java, when reading in a file one character at a time, how do I determine EOF?
提问by art3m1sm00n
I am having to read in a while and use an algorithm to code each letter and then print them to another file. I know generally to find the end of a file you would use readLine and check to see if its null. I am using a bufferedReader. Is there anyway to check to see if there is another character to read in? Basically, how do I know that I just read in the last character of the file?
我不得不阅读一段时间并使用算法对每个字母进行编码，然后将它们打印到另一个文件中。我通常知道要找到文件的结尾，您将使用 readLine 并检查它是否为空。我正在使用一个缓冲阅读器。无论如何要检查是否有另一个字符可以读入？基本上，我怎么知道我刚刚读入了文件的最后一个字符？
I guess i could use readline and see if there was another line if I knew how to determine when I was at the end of my current line.
我想我可以使用 readline 并查看是否还有另一行，如果我知道如何确定我何时处于当前行的末尾。
I found where the File class has a method called size() that supposidly turns the length in bytes of the file. Would that be telling me how many characters are in the file? Could i do while(charCount<length)?
我发现 File 类有一个名为 size() 的方法，它可以转换文件的字节长度。这会告诉我文件中有多少个字符吗？我可以while(charCount<length)吗？
回答by gd1
I don't exactly understand what you want to do. I guess you may want to read a file character by character. If so, you can do:
我不完全明白你想做什么。我猜您可能想逐个字符地读取文件。如果是这样，你可以这样做：
FileInputStream fileInput = new FileInputStream("file.txt");
int r;
while ((r = fileInput.read()) != -1) {
char c = (char) r;
// do something with the character c
}
fileInput.close();
FileInputStream.read()returns -1when there are no more characters to read. It returns an intand not a charso a cast is mandatory.
FileInputStream.read()-1当没有更多字符要读取时返回。它返回一个int而不是一个char所以强制转换是强制性的。
Please note that this won't work if your file is in UTF-8 format and contains multi-byte characters. In that case you have to wrap the FileInputStreamin an InputStreamReaderand specify the appropriate charset. I'm omitting it here for the sake of simplicity.
请注意，如果您的文件是 UTF-8 格式并且包含多字节字符，这将不起作用。在这种情况下，您必须将 包装FileInputStream在 an 中InputStreamReader并指定适当的字符集。为了简单起见，我在这里省略了它。
回答by Saquib Mian
From my understanding, buffers will return -1 if there are no characters left. So you could write:
根据我的理解，如果没有剩余字符，缓冲区将返回 -1。所以你可以写：
BufferedInputStream in = new BufferedInputStream(new FileInputStream("filename"));
while (currentChar = in.read() != -1) {
//do something
}
in.close();
