Does Files.readAllBytes() closes the inputstream after reading the file?

Yes, it closes. See it in the javadoc.

Reads all the bytes from a file. The method ensures that the file is closed when all bytes have been read or an I/O error, or other runtime exception, is thrown.

Note that this method is intended for simple cases where it is convenient to read all bytes into a byte array. It is not intended for reading in large files.

public static byte[] readAllBytes(Path path) throws IOException {
    try (SeekableByteChannel sbc = Files.newByteChannel(path);
         InputStream in = Channels.newInputStream(sbc)) {
        long size = sbc.size();
        if (size > (long)MAX_BUFFER_SIZE)
            throw new OutOfMemoryError("Required array size too large");

        return read(in, (int)size);
    }
}