In the README.md it is written:
You need to fill in the twitter4j.properties file with your own credentials.
The Java application cannot find the file and a NPE is returned.
(in is null and prop.load(in) generates a NPE!)
Crawler.java:
try { InputStream in = Crawler.class.getClassLoader() .getResourceAsStream("twitter4j.properties"); prop.load(in); } catch (IOException e) { log.error(e.toString()); }