Java: Appendable byte array

Question

I want to append bytes to an byte array. The result should be type byte[] , with adding single byte 's after calculating them, to it. So my question is: What is the best and/or efficient way to accomplish that? How to write to that?

Answer 1

Use ByteArrayOutputStream. This has a toByteArray() method when you are done

http://docs.oracle.com/javase/7/docs/api/java/io/ByteArrayOutputStream.html

Answer 2

I would suggest using of Guava's ByteSource

http://docs.guava-libraries.googlecode.com/git/javadoc/com/google/common/io/ByteSource.html

It is much more efficient because of using a chains of small chunks inside instead of reallocating memory for a huge array (as ByteArrayOutputStream does).

Here is an example:

byte[] buffer = new byte[1024]; 

List<ByteSource> loaded = new ArrayList<ByteSource>();

    while (true) {
        int read = input.read(buffer);
        if (read == -1) break;
        loaded.add(ByteSource.wrap(Arrays.copyOf(buffer, read)));
    }

ByteSource result = ByteSource.concat(loaded)