title: what are those files with "~" in java projects?
body: <p>I've never seen that,internally generated?How does it work?</p>
  
  <p>Can check what I meen here:
  <a href="http://issues.apache.org/jira/secure/attachment/12401970/nutch_0.9_OR.patch" rel="nofollow noreferrer">http://issues.apache.org/jira/secure/attachment/12401970/nutch_0.9_OR.patch</a></p>
  
  <p>search "java~"</p>
  
  <p>and you can see "java.old" there,what's that again?</p>