We always end up working with files when writing a meaningful application. Java has a tremendous API for handling files and they do the job most of the times. This post is to point out one of the most common reasons we get java .io.FileNotFoundException.
A call to new FileOutputStream(file) throws either a security exception or a FileNotFoundException.
Ideally when you created a file using
File file = new File(fileName) you will hope a error to be thrown, but that will not happen as this call doesn’t actually create a physical file on the disk (you need to call createNewFile()) to create a physical file.
Now if you are chaining this file reference and passing it to FileOutputStream hoping all to work like dream, you might be in for a surprise if the File you provided has INVALID characters in the file name. If you have invalid characters the call to new FileOutputStream(file) will throw a file not found exception and you will be wasting precious time debugging what went wrong.
So the rule of thumb is to have a static function somewhere to check for your file name for invalid characters, and make sure to run your file name by this function to prevent the i/o errors.
Invalid file name characters
The following are not allowed as file name characters in windows world
\ / : * ? ” < > |
For more information check the following link:
http://support.microsoft.com/kb/177506
Sample File Name Purifier Program
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final String[] invalidChars = new String[]{“/”,”\”,”:”,”*”,”?”,”<“,”>”,”|”};
public static final String purifyFileName(String name) {
if (name == null || name==””) return;
String returnName = name;
for(String str : invalidChars) {
returnName = returnName.replace(str,’ ‘);
}
return returnName;
}
}
The above is just a sample implementation and you can come up with better and more efficient implementations of your own.
