How do I check if a file exists in Java?

Question

How can I check whether a file exists, before opening it for reading in Java (the equivalent of Perl's -e $filename)?

The only similar question on SO deals with writing the file and was thus answered using FileWriter which is obviously not applicable here.

If possible I'd prefer a real API call returning true/false as opposed to some "Call API to open a file and catch when it throws an exception which you check for 'no file' in the text", but I can live with the latter.

Solution 1

Using java.io.File:

File f = new File(filePathString);
if(f.exists() && !f.isDirectory()) { 
    // do something
}

Solution 2

I would recommend using isFile() instead of exists(). Most of the time you are looking to check if the path points to a file not only that it exists. Remember that exists() will return true if your path points to a directory.

new File("path/to/file.txt").isFile();

new File("C:/").exists() will return true but will not allow you to open and read from it as a file.

Solution 3

By using nio in Java SE 7,

import java.nio.file.*;

Path path = Paths.get(filePathString);

if (Files.exists(path)) {
  // file exist
}

if (Files.notExists(path)) {
  // file is not exist
}

If both exists and notExists return false, the existence of the file cannot be verified. (maybe no access right to this path)

You can check if path is a directory or regular file.

if (Files.isDirectory(path)) {
  // path is directory
}

if (Files.isRegularFile(path)) {
  // path is regular file
}

Please check this Java SE 7 tutorial.

Solution 4

Using Java 8:

if(Files.exists(Paths.get(filePathString))) { 
    // do something
}

Solution 5

File f = new File(filePathString); 

This will not create a physical file. Will just create an object of the class File. To physically create a file you have to explicitly create it:

f.createNewFile();

So f.exists() can be used to check whether such a file exists or not.

View more solutions

Comments

[Sean A.O. Harney]

There is no need to check if f != null before checking f.exists, if the new keyword fails it will generate an Exception.

[just somebody]

there's no check if f != null. f + (...) uses java.io.File.toString

[demongolem]

Way to not answer the question. I agree commons has a lot of useful stuff, but maybe we could take that one step further and provide an answer to the question the OP asked.

[bulltorious]

He gave enough of an answer for me.

[lmat - Reinstate Monica]

Does pearl's -e also ensure that the application "can read" the file?

[GreenGiant]

@just actually, it uses String.valueOf(), which handles nulls

[Doug Hauf]

What if I want to check every hour to see if a file has been deposited on a directly location. I have a webMethods project that has to check to see if a specific file has been uploaded to a specific drive. How would this be done. Let's say that I want to check every hour to see if the file is there. I can use Java to write a class that does this probably with a timer of some sort.

[Nick Frolov]

Catching an exception is way more expensive. In my test, checking new File().exists() was more than 10 times faster than catching FileNotFoundException. So, if you have a scenario where files normally expected to be missing (such as disk cache), exception is wrong. Also, second-guessing the system is cool.

[user207421]

@Gnawer You haven't addressed any of the issues I raised; the exception is only thrown when the file can't be opened; and operations that occur once an hour don't require micro-optimization. Your final sentence is nonsense.

[Matthew Read]

@ylun.ca The example includes subdirectories? If you mean to ask whether, given a current directory of /path, new File("file.txt").exists() will return true if the correct full path is /path/to/file.txt, the answer is a big no (unless another file /path/file.txt exists).

[Raghu K Nair]

What is the advatages compared to new File(path).exists() ? For a palin exists check

[CAW]

There are some cases where exists() will return an incorrect result. For example, when using an NFS file system there is an issue with stale file handles: bugs.java.com/bugdatabase/view_bug.do?bug_id=5003595 It's kind of obscure, but has been the cause of some frustrating bugs in production code before.

[Matthieu]

@RaghuKNair java.nio.file.Files.exists() is a lot faster than java.io.File.exists() (from my small benchmark on the only computer I tested: Windows Server 2012 running Java 1.7.0_45 x64).

[Mike C]

Files.exists() takes two arguments. Typically, you'll want something like Files.exists(path, LinkOption.NOFOLLOW_LINKS ).

[PowerFlower]

@MikeC I wonder which method gets called without the second argument. The Docu doesn't even show any information about that.

[Dan Passaro]

@DougHauf in your case there's no issue since you don't attempt to do anything after you check existence. But the OP asked specifically to check before opening. In this case it's better to just try/catch the file open.

[ParkerHalo]

I just tried it myself and java.nio.file.Files.exists() was 5 times SLOWER than java.io.File.exists. (Win7 Java 1.7.0_79 - x86)

[TK8]

@PowerFlower: There is only one Files.exists() method. Without passing the second argument, it still calls the same method. The second argument is varargs variable and can pass 0 or more LinkOptions.

[Genaut]

From sonar docs: 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. The same goes for Files.notExists, Files.isDirectory and Files.isRegularFile. The best alternative to this is: path.toFile().exists()

[Richard]

This also has the disadvantage that Paths.get throws an exception if the string isn't valid

[user207421]

May not work why not? And how does using a URI fix that?

[iviorel]

We had an issue. f.exists() was true and we even could get the file content. The problem was, the path was wrong but the file name was OK, even this was another file. Changing the constructor call with URI, fixed the problem.

[Leon]

Use if(f.isFile()) instead.

[Asim]

remember to use filePathString.trim() to avoid white spaces

[Cristian]

To take into account your answer has the best performance compared with File.is Exist() orFiles.isRegularFile() in JDK 8

[user207421]

The question is about opening it for reading, not writing, and in any case this is certainly not 'good coding practice'.

[user207421]

Hard to believe. Using a URI and changing \ to / can't have that effect. You must have fixed something else at the same time.

[Lii]

Duplicate of an earlier answer.

[qualebs]

It is not uncommon to find Apache Commons Libs are already in use in most projects. I think this answer is very helpful. I can't count the number of times I reinvented the wheel before I finally started using Apache Commons. +1 from me

[tedtanner]

To clarify @Leon's response, f.isFile() returns false if f is a directory or if it doesn't exist. Thus, it is (mostly) equivalent to f.exists() && !f.isDirectory(), though the latter expresses intent more explicitly.