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.
This question is related to
java
file-io
io
file-exists
There are multiple ways to achieve this.
In case of just for existence. It could be file or a directory.
new File("/path/to/file").exists();
Check for file
File f = new File("/path/to/file");
if(f.exists() && f.isFile()) {}
Check for Directory.
File f = new File("/path/to/file");
if(f.exists() && f.isDirectory()) {}
Java 7 way.
Path path = Paths.get("/path/to/file");
Files.exists(path) // Existence
Files.isDirectory(path) // is Directory
Files.isRegularFile(path) // Regular file
Files.isSymbolicLink(path) // Symbolic Link
Using Java 8:
if(Files.exists(Paths.get(filePathString))) {
// do something
}
There is specific purpose to design these methods. We can't say use anyone to check file exist or not.
Don't use File constructor with String.
This may not work!
Instead of this use URI:
File f = new File(new URI("file:///"+filePathString.replace('\\', '/')));
if(f.exists() && !f.isDirectory()) {
// to do
}
Simple example with good coding practices and covering all cases :
private static void fetchIndexSafely(String url) throws FileAlreadyExistsException {
File f = new File(Constants.RFC_INDEX_LOCAL_NAME);
if (f.exists()) {
throw new FileAlreadyExistsException(f.getAbsolutePath());
} else {
try {
URL u = new URL(url);
FileUtils.copyURLToFile(u, f);
} catch (MalformedURLException ex) {
Logger.getLogger(RfcFetcher.class.getName()).log(Level.SEVERE, null, ex);
} catch (IOException ex) {
Logger.getLogger(RfcFetcher.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
Reference and more examples at
https://zgrepcode.com/examples/java/java/nio/file/filealreadyexistsexception-implementations
Don't. Just catch the FileNotFoundException.
The file system has to test whether the file exists anyway. There is no point in doing all that twice, and several reasons not to, such as:
Don't try to second-guess the system. It knows. And don't try to predict the future. In general the best way to test whether any resource is available is just to try to use it.
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.
f.isFile() && f.canRead()
I know I'm a bit late in this thread. However, here is my answer, valid since Java 7 and up.
The following snippet
if(Files.isRegularFile(Paths.get(pathToFile))) {
// do something
}
is perfectly satifactory, because method isRegularFile
returns false
if file does not exist. Therefore, no need to check if Files.exists(...)
.
Note that other parameters are options indicating how links should be handled. By default, symbolic links are followed.
You can use the following: File.exists()
You can make it this way
import java.nio.file.Paths;
String file = "myfile.sss";
if(Paths.get(file).toFile().isFile()){
//...do somethinh
}
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.
For me a combination of the accepted answer by Sean A.O. Harney and the resulting comment by Cort3z seems to be the best solution.
Used the following snippet:
File f = new File(filePathString);
if(f.exists() && f.isFile()) {
//do something ...
}
Hope this could help someone.
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.
It's also well worth getting familiar with Commons FileUtils https://commons.apache.org/proper/commons-io/javadocs/api-2.5/org/apache/commons/io/FileUtils.html This has additional methods for managing files and often better than JDK.
first hit for "java file exists" on google:
import java.io.*;
public class FileTest {
public static void main(String args[]) {
File f = new File(args[0]);
System.out.println(f + (f.exists()? " is found " : " is missing "));
}
}
Source: Stackoverflow.com