public synchronized String
toMasterFile() {
	Iterator zentries = data.entrySet().iterator();
	StringBuffer sb = new StringBuffer();
	nodeToString(sb, originNode);
	while (zentries.hasNext()) {
		Map.Entry entry = (Map.Entry) zentries.next();
		if (!origin.equals(entry.getKey()))
			nodeToString(sb, entry.getValue());
	}
	return sb.toString();
}
Returns the contents of the Zone in master file format.
src/main/java/core/org/xbill/DNS/Zone.java