对于isDirectory，文件返回false，而Java中的isFile

Question

Why file returns false for isFile() method, even when it is file. And when it is directory, it returns false for isDirectory() . Am I doing something wrong? These files/directories I test don't exists, and I need to create these, so that is why I am testing if I should use createFile() or mkdir() .

File file = new File("C:/Users/John/Desktop/MyDir/file.txt");
if(!file.exists())
{
    System.out.println("Is directory : " + file.isDirectory());         
    System.out.println("Is file : " + file.isFile());
}

Answer 1

In your if you're checking if the file doesn't exist. If it doesn't exist then it's neither a file nor a directory.

Java can't determine if your File object is a file or a directory only with a path string. The String could mean a file or a directory (you can have a folder named "file.txt" or a file with the same name).

Answer 2

What you are doing is saying if it doesn't exist. If it doesn't exist it is neither a file or directory. Your logic must be wrong as you should use:

if(file.exists()){

Answer 3

You're using isDirectory() and isFile() on a file object that doesn't exist. Both of these methods return false if the specified file does not exist yet, as per the documentation.

Answer 4

Your program only prints out if if(!file.exists()) , which means that if the file doesn't exist, it will then tell you if file.isFile() . That is, because the file doesn't exist then your program only prints out False.

Answer 5

How can it be a file or a directory until it exists? In Linux and Windows (though Explorer itself doesn't allow you to include a . ), file.txt is a valid name for both a file and a directory, so Java couldn't possibly know how you (or your user) intended to use it.