public static void copy(InputStream in, OutputStream out, byte[] buf) throws IOException {
		int r;
		while ((r = in.read(buf)) != -1)
			out.write(buf, 0, r);
	}
Transfers content of {@link InputStream} into {@link OutputStream}.

@param in
		Stream to transfer content from.
@param out
		Stream to transfer content to.
@param buf
		Buffer that is used to hold data.

@throws IOException
		When any I/O error occurs.
recaf-core/src/main/java/software/coley/recaf/util/IOUtil.java