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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

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  • 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. Commented Mar 16, 2021 at 6:47
  • 1
    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 tutorials.jenkov.com/java-zip/zipfile.html Commented Mar 16, 2021 at 6:47
  • 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. Commented Mar 16, 2021 at 6:52
  • 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 Commented Mar 16, 2021 at 6:53
  • Not necessarily. What datatype are you using for the version field? And how is an entire zip file a version? Commented Mar 16, 2021 at 6:55

1 Answer 1

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1

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;
    }
}
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