Java: How to check that 2 binary files are same?

Question

What is the easiest way to check (in a unit test) whether binary files A and B are equal?

Answer 1

Read the files in (small) blocks and compare them:

static boolean binaryDiff(File a, File b) throws IOException {
    if(a.length() != b.length()){
        return false;
    }

    final int BLOCK_SIZE = 128;
    InputStream aStream = new FileInputStream(a);
    InputStream bStream = new FileInputStream(b);
    byte[] aBuffer = new byte[BLOCK_SIZE];
    byte[] bBuffer = new byte[BLOCK_SIZE];
    while (true) {
        int aByteCount = aStream.read(aBuffer, 0, BLOCK_SIZE);
        bStream.read(bBuffer, 0, BLOCK_SIZE);
        if (aByteCount < 0) {
            return true;
        }
        if (!Arrays.equals(aBuffer, bBuffer)) {
            return false;
        }
    }
}