How to read a large zip file data in byte array?

Question

I am reading a large zip file but my code giving me negative array size exception

    // Simplest read of an entire file into a byte array
     // Will throw exceptions for file not found etc.
    private static byte[] loadFileAsByteArray(String path) throws IOException {
    File file = new File(path);
    InputStream is = new FileInputStream(file);
    byte[] data = new byte[(int) file. Length()];
    is.read(data);
    return data;
}

Please tell me how I can read a long zip file data in bytes

Can you add the exception to your question? NOTE: `file.length()` can legitimately return 0 (if you have the wrong file or a special file) and it's undefined what happens if you gave a "path" rather than file to that call. — Mr R, Mar 16 '21 at 06:47
is htere a reason you want to read the zip file instead of using ```ZipFile``` and ```ZipEntry``` that handle zip files better? Take a look at http://tutorials.jenkov.com/java-zip/zipfile.html — Yogesh_D, Mar 16 '21 at 06:47
And is there a reason why you need the entire file in memory? The larger the file the worse this is as an idea, but it is never necessary. — user207421, Mar 16 '21 at 06:52
We want to upload that zip file inside salesforce contentversion so to add body of zip file inside a version data field in contentversion we need to read the zip file in bytes — Aakash jain, Mar 16 '21 at 06:53
Not necessarily. What datatype are you using for the `version` field? And how is an entire `zip` file a version? — user207421, Mar 16 '21 at 06:55
Have you considered consulting the [Javaodc](https://docs.oracle.com/javase/8/docs/api/java/sql/Blob.html)? — user207421, Mar 16 '21 at 07:12
Your code doesnt even compile (it is l enght, not Length). It does not contain a real [mcve]. It doesn't show any prior research, just a "here is a bit of code that doesnt compile" and a vague problem description. Without all these details, the best answer is "read EXISTING material how to read files in java", and work from there. — GhostCat, Mar 16 '21 at 07:26

score 1 · Answer 1 · answered Mar 16 '21 at 07:22

Your code has at least 1 error:
file. Length() does not deliver the result you want.
(and indeed will probably not compile at all)
Presumably what you want is file.length()

To your problem:
you can only get a negative array-size if the file you're reading is over 2,147,483,647 bytes long.
In that case, casting to int yields a negative value.

Also: even if your array is large enough to contain all the data, there is no guarantee is.read(data); will read it all in one go. You need a loop.

Finally: remember to use try-with-resources to close the InputStream & make final variables final.

How about this?:

private static byte[] loadFileAsByteArray(final String path) throws IOException {

    final File file = new File(path);

    try (final InputStream is = new FileInputStream(file)) {

        final byte[]  data = new byte[(int) file.length()]; // Cast -> -ve Array-Size?

        int           off  = 0;
        int           len;

        while (-1 != (len = is.read(data, off, data.length - off))) {
            off   +=  len;
        }
        return  data;
    }
}

How to read a large zip file data in byte array?

1 Answers1