throws IOException {
// Build the corresponding phone prefix map and serialize it to the binary format.
PhonePrefixMap phonePrefixMap = new PhonePrefixMap();
phonePrefixMap.readPhonePrefixMap(sortedMap);
ObjectOutputStream objectOutputStream = new ObjectOutputStream(output);
phonePrefixMap.writeExternal(objectOutputStream);
objectOutputStream.flush();
}
/**
* Reads the mappings contained in the provided input stream pointing to a text file.