title: How JVM works when two same jar be included in classpath
body: <p>It was a mistake of my co-worker:  there was a jar named test.jar and he has fixed a bug of it.  Then he re-compile the code and built a new jar named testnew.jar
  The problem was he put these two jar into one folder which in classpath.
  So when program was running, the behavior was a kind of mess.  I didn't know what had happened but after removing test.jar, everthing was fine again.</p>
  
  <p>So I'm wondering what's the behavior of JVM.  Does it use the class file in first jar it meet?  Or something else? </p>
  
  <p>Thanks.</p>