title: I use Spring-core 4.3.3, but still have ClassNotFound error for ConfigurableEnvironment
body: <p>I've created a SpringBoot application and ran into this when trying to launch it:</p>
  
  <pre><code>Exception in thread "main" java.lang.NoClassDefFoundError: org/springframework/core/env/ConfigurableEnvironment
  at com.example.DemoApplication.main(DemoApplication.java:10)
  Caused by: java.lang.ClassNotFoundException: org.springframework.core.env.ConfigurableEnvironment
  at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
  at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
  at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
  at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
  ... 1 more
  </code></pre>
  
  <p>I understand it means ConfigurableEnvironment wasn't found in the classpath or the jar containing it not in the classpath. However I doubt this is even the case. I looked up the doc and knew this class is from Spring-core since 3.1, mine in the classpath is 4.3.3, and I double checked like below:</p>
  
  <pre><code> jar tvf spring-core-4.3.3.RELEASE.jar | grep ConfigurableEnvironment
   732 Mon Sep 19 14:50:30 EDT 2016  org/springframework/core/env/ConfigurableEnvironment.class
  </code></pre>
  
  <p>I looked up google and came across this web tool, <a href="https://start.spring.io/" rel="nofollow">Spring initilizer</a> and I used it to create the most simple and unpolluted SpringBootApplication, still, it gives me the same error.</p>
  
  <p>I admit I am at my wit end, anyone kindly advice please.</p>