Java 检查文件是否为空：IOException: null
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Java check if file is empty: IOException: null
提问by NGix
I'm trying to load a file to my ArrayList, program creates a file if it doesn't exist. I'm getting IOException: Null as at the beginning file is empty. How I can avoid that error and check if file is empty or not? Here's my code:
我正在尝试将文件加载到我的 ArrayList，如果文件不存在，程序会创建一个文件。我收到 IOException: Null 因为开头的文件是空的。如何避免该错误并检查文件是否为空？这是我的代码：
File f = new File(fileName);
try {
if( !f.exists() ){
f.createNewFile();
}
inputStream = new ObjectInputStream(new FileInputStream(f));
scores = (ArrayList<Score>) inputStream.readObject();
} catch (IOException e) {
System.out.println("IO Error: " + e.getMessage());
} finally {
...
}
回答by hmjd
Use File.length()to obtain the size number of bytes of the file:
使用File.length()获得文件的字节大小数：
The length, in bytes, of the file denoted by this abstract pathname, or 0L if the file does not exist. Some operating systems may return 0L for pathnames denoting system-dependent entities such as devices or pipes.
此抽象路径名表示的文件的长度（以字节为单位），如果文件不存在，则为 0L。某些操作系统可能会为表示系统相关实体（例如设备或管道）的路径名返回 0L。
回答by Vorsprung
It seems to me your program needs a minor bit of restructuring, then it won't try and load the empty file
在我看来你的程序需要一点点重组，然后它不会尝试加载空文件
File f = new File(fileName);
try {
if( f.length() == 0 ){
f.createNewFile();
} else {
inputStream = new ObjectInputStream(new FileInputStream(f));
scores = (ArrayList<Score>) inputStream.readObject();
}
} catch (IOException e) {
System.out.println("IO Error: " + e.getMessage());
} finally {
...
