See if file is empty

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Most efficient way to check if a file is empty in Java on Windows

How to a check if a file is empty in Java 7?
I tried it using the available() method from ObjectInputStream, but it returns always zero even if the the file contains data.

score 36 · Accepted Answer · answered Apr 23 '12 at 13:26

36

File file = new File("file_path");
System.out.println(file.length());

answered Apr 23 '12 at 13:26

Uchenna Nwanyanwu

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A tricky solution since Java 7 is to use the java.nio.Files class. Then, you can perform the same in one line. For example: `System.out.println(Files.size(Paths.get("file_path")));` – daniel souza Apr 18 '15 at 22:50
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Doesn't for for Unicode files (see answer in duplicate message for details). – Kalle Richter Jan 08 '17 at 15:12

Jack · Answer 2 · 2012-04-23T18:11:27.500

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File file = new File(path);

boolean empty = !file.exists() || file.length() == 0;

which can shortened to:

boolean empty = file.length() == 0;

since according to documentation the method returns

The length, in bytes, of the file denoted by this abstract pathname, or 0L if the file does not exist

edited Apr 23 '12 at 18:11

answered Apr 23 '12 at 13:23

Jack

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Hey @Jack, I think it should rather be as my answer below. Correct me if I am wrong. – TechSpellBound Apr 23 '12 at 16:58
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It depends upon why you need to check if a file it's empty. You could need either to consider a non existent file as empty or not. So your answer could be as correct as mine, not rather. – Jack Apr 23 '12 at 17:13
But I feel that even in that case, if the file does not exist, we don't have to check if its empty or not. So, for a non-existing file, my answer saves a call to file.length(). Minor improvement in efficiency but I feel it's logical. Please correct me if I am wrong. – TechSpellBound Apr 23 '12 at 17:20
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In your snippet, if file doesn't exists then `empty == false`. In my snippet if file doesn't exist first condition evaluates to true, so the length of the file it's not checked too, but the result is different (remember that this is an `||`, laziness of evaluation applies to both `&&` and `||`operators). – Jack Apr 23 '12 at 18:08
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In addition there's no need to check for existence in any case, since `file.length()` returns `0` if file doesn't exist, it's just for a matter of readability. – Jack Apr 23 '12 at 18:10

score 4 · Answer 3 · answered Apr 23 '12 at 17:01

4

File file = new File(path);

boolean empty = file.exists() && file.length() == 0;

I want to stress that if we want to check if the file is empty, then we have to consider that it exists.

answered Apr 23 '12 at 17:01

TechSpellBound

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I think this one is the correct answer. If you check the javadocs of the length method it says that it will return 0 if the file is "invalid". – Lakatos Gyula Aug 02 '18 at 18:26

score 2 · Answer 4 · edited May 23 '17 at 12:17

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BufferedReader br = new BufferedReader(new FileReader("your_location"));     
if (br.readLine()) == null ) {
    System.out.println("No errors, and file empty");
}

see Most efficient way to check if a file is empty in Java on Windows

edited May 23 '17 at 12:17

Community

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answered Apr 23 '12 at 13:23

Oritm

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@sans481 the linked post pretty much enumerates every method known to man. Most of those methods generally work and are correct, just the OP there had a very specific problem: a file that was actually **not empty** (had a two-byte BOM in it) was to be considered as empty. – Marko Topolnik Apr 23 '12 at 13:34
Now I clearly understood your opinion. Yes, its really a disaster to read a whole line just to tell whether or not a file is empty. Situation becomes worse if the first line is huge. Thanks! – sgowd Apr 23 '12 at 13:40

Nicocube · Answer 5 · 2012-04-23T13:28:45.427

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According to J2RE javadocs: http://docs.oracle.com/javase/7/docs/api/java/io/File.html#length()

public long length()
    Returns the length of the file denoted by this abstract pathname. The return value is     unspecified if this pathname denotes a directory.

So new File("path to your file").length() > 0 should do the trick. Sorry for bd previous answer. :(

edited Apr 23 '12 at 13:28

answered Apr 23 '12 at 13:23

Nicocube

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score 0 · Answer 6 · answered Apr 23 '12 at 13:28

        File file = new File("path.txt");
        if (file.exists()) {
            FileReader fr = new FileReader(file);
            if (fr.read() == -1) {
                System.out.println("EMPTY");
            } else {
                System.out.println("NOT EMPTY");
            }
        } else {
            System.out.println("DOES NOT EXISTS");
        }

See if file is empty

6 Answers6

Linked