why use ByteArrayOutputStream

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Hi, My solution didn't pass (althought it worked on my computer,for what I could see) until I take a look at the help section and test the ByteArrayOutputStream In my solution, to save content of the differents ZipEntry I used a buffer sized thanks the ZipEntry class getSize method and success to store in it the content by using the read(byte[]) method of ZipInputStream, and later I used this buffer to write in the corresponding file in the new folder zip Why doesn't it work like this ? My solution :

while ((ze = zipIn.getNextEntry()) != null) {
     byte [] b = new byte[(int) ze.getSize()];

     zipIn.read(b);
     zipEntries.put(ze,b)
}

Solution which passed :

while ((ze = zipIn.getNextEntry()) != null) {
     byte[] buffer = new byte[1024];
     ByteArrayOutputStream builder = new ByteArrayOutputStream();
     int end;
     while ((end = zipIn.read(buffer)) > 0) {
          builder.write(buffer, 0, end);
     }
     zipEntries.put(ze, builder.toByteArray());
}

Thanks a lot for your help, and sorry for bad english.

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Guadalupe Gagnon

Level 37 , Tampa, United States

9 March 2021, 15:26

useful

ZipEntry.getSize() returns the uncompressed size of the ZipFile. You will be reading in the compressed bytes though, so the buffer in the top would be too large. I think you would be able to make it work though like this:

while ((ze = zipIn.getNextEntry()) != null) {
     byte [] b = new byte[(int) ze.getSize()];

     int end = zipIn.read(b);
     zipEntries.put(ze,Arrays.copyOfRange(b, 0, end))
}

but the getSize() method can also return -1 and that would result in an exception being thrown on the Array initialization line.

Romain

Level 26 , Paris, France

9 March 2021, 16:04

Thanks for your answer (again), I was doing it on purpose to use the uncompressed size, I thought the read and write actions should be done on files uncompressed, and then the compression was doing by itself... ^^ Just, in your explaination why do you think it's necessary to use copyOf Range and "end", Can't I use my buffer "b" directly ?

Guadalupe Gagnon

Level 37 , Tampa, United States

9 March 2021, 17:10

useful

After some testing it seems that the ZipInputStream has a max amount of bytes that can be read at one time. I have been testing with a zip file that contains only 1 file in it. The compressed size of the that ZipEntry is 1691 while the uncompressed size is 7793. No matter what length I set my buffer to, 1961 or 7793 (or any number greater than 1402), it maxes out at reading 1402 bytes at one time. The only way that I get all the bytes from it is by reading in a loop until all the bytes have been read, such as the second example you shared above.