CODEWITHSUNDEEP
javafile-io
user1191027
user1191027

Reputation:

Check if file exists without creating it

If I do this:

File f = new File("c:\\text.txt");

if (f.exists()) {
    System.out.println("File exists");
} else {
    System.out.println("File not found!");
}

Then the file gets created and always returns "File exists". Is it possible to check if a file exists without creating it?

EDIT:

I forgot to mention that it's in a for loop. So here's the real thing:

for (int i = 0; i < 10; i++) {
    File file = new File("c:\\text" + i + ".txt");
    System.out.println("New file created: " + file.getPath());
}

Upvotes: 27

Views: 90020

Answers (5)

brianko
brianko

Reputation: 1

As of Java 11, any of these code snippets that use Paths.get("some_path") do not work, as the Paths.get() call actually creates the directory (at least in Windows), so the return value of, for example, Paths.get("some_path").toFile().exists() is immediately outdated as soon as it is generated.

Upvotes: 0

Denys S&#233;guret
Denys S&#233;guret

Reputation: 382454

When you instantiate a File, you're not creating anything on disk but just building an object on which you can call some methods, like exists().

That's fine and cheap, don't try to avoid this instantiation.

The File instance has only two fields:

private String path;
private transient int prefixLength;

And here is the constructor :

public File(String pathname) {
    if (pathname == null) {
        throw new NullPointerException();
    }
    this.path = fs.normalize(pathname);
    this.prefixLength = fs.prefixLength(this.path);
}

As you can see, the File instance is just an encapsulation of the path. Creating it in order to call exists() is the correct way to proceed. Don't try to optimize it away.

Upvotes: 54

Kelevra
Kelevra

Reputation: 71

The Files.exists method has noticeably poor performance in JDK 8, and can slow an application significantly when used to check files that don't actually exist.

This can be applied too for Files.noExists, Files.isDirectory and Files.isRegularFile

According this you can use the following : 

Paths.get("file_path").toFile().exists()

Upvotes: 3

ROMANIA_engineer
ROMANIA_engineer

Reputation: 56714

Starting from Java 7 you can use java.nio.file.Files.exists:

Path p = Paths.get("C:\\Users\\first.last");
boolean exists = Files.exists(p);
boolean notExists = Files.notExists(p);

if (exists) {
    System.out.println("File exists!");
} else if (notExists) {
    System.out.println("File doesn't exist!");
} else {
    System.out.println("File's status is unknown!");
}

In the Oracle tutorial you can find some details about this:

The methods in the Path class are syntactic, meaning that they operate on the Path instance. But eventually you must access the file system to verify that a particular Path exists, or does not exist. You can do so with the exists(Path, LinkOption...) and the notExists(Path, LinkOption...) methods. Note that !Files.exists(path) is not equivalent to Files.notExists(path). When you are testing a file's existence, three results are possible:

  • The file is verified to exist.
  • The file is verified to not exist.
  • The file's status is unknown. This result can occur when the program does not have access to the file.

If both exists and notExists return false, the existence of the file cannot be verified.

Upvotes: 14

hmjd
hmjd

Reputation: 122001

Creating a File instance does not create a file on the file system, so the posted code will do what you require.

Upvotes: 11

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