Question

I’m trying to implement this algorithm description from a previous question I had here in stackoverflow:

suppressing or not allowing the access time to be modified java

so I implemented as

byte[] digest = new byte[this.BUFFER];
        MessageDigest md5;

        try {
            md5 = MessageDigest.getInstance("MD5");

            while(entry.getNextEntry() != null){

                ZipEntry current = entry.getNextEntry();

                if(current.isDirectory()){
                    digest = this.encodeUTF8(current.getName());
                    md5.update(digest);
                }
                else{
                        entry.read(digest, 0, this.BUFFER);
                        md5.update(digest);
                }
            }
            digest = md5.digest();
            entry.close();
        } catch (NoSuchAlgorithmException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

However, I’m getting a Exception in thread “main” java.lang.IndexOutOfBoundsException in the else statement. Does someone know why? Also, could you please tell me if my algorithm was correctly implemented?

Answer 1

You’re calling getNextEntry() twice, instead of once:

while (entry.getNextEntry() != null) { // goes to the next entry
    ZipEntry current = entry.getNextEntry(); // goes to the next entry

Use this instead:

ZipEntry current;
while ((current = entry.getNextEntry()) != null) {
    // use current   
}

or

for (ZipEntry current = entry.getNextEntry(); current != null; current = entry.getNextEntry()) {
    // use current
}