title: Eclipse Oxygen This compilation unit is not on build path of java project
body: <p>I have created a Kafka Streams Project using Maven Archetype:</p>
  
  <pre><code>mvn archetype:generate \
  -DarchetypeGroupId=org.apache.kafka \
  -DarchetypeArtifactId=streams-quickstart-java \
  -DarchetypeVersion=1.0.0 \
  -DgroupId=streams.examples \
  -DartifactId=streams.examples \
  -Dversion=0.1 \
  -Dpackage=myapps
  </code></pre>
  
  <p>Compiling and running the program:</p>
  
  <pre><code>&gt; mvn clean package
  &gt; mvn exec:java -Dexec.mainClass=myapps.Pipe
  </code></pre>
  
  <p>The program works fine.</p>
  
  <p>However when I am editing the code and try <code>Ctrl+Space</code> I am getting <code>Cannot perform operation</code> error:</p>
  
  <pre><code>This compilation unit is not on build path of java project.
  </code></pre>
  
  <p><strong>See the image below:</strong></p>
  
  <p><a href="https://i.stack.imgur.com/S40Km.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/S40Km.png" alt="enter image description here"></a></p>