title: Issue with Maven project in vs code
body: <p>See the attached snapshots. I cloned this project and having issues working with this project in vs code:</p>
  <p><a href="https://github.com/javalite/jar-explorer" rel="nofollow noreferrer">https://github.com/javalite/jar-explorer</a></p>
  <ol>
  <li>Sometimes, the Maven tab or sub-view under the Explorer View is hidden. I did something that enable to section to show but I don't remember how. How I can show this Maven View if it is hidden?</li>
  </ol>
  <p><a href="https://i.stack.imgur.com/HE6bF.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/HE6bF.png" alt="enter image description here" /></a></p>
  <ol start="2">
  <li>The project was built successfully using the command line <code>mvn clean install</code>, however, the vs code problem view was showing strange errors. I then notice the the POM.xml file didn't have this line at the top:</li>
  </ol>
  <pre><code>&lt;?xml version=&quot;1.0&quot; encoding=&quot;UTF-8&quot;?&gt;
  </code></pre>
  <p>Following is a sample of the errors I saw:</p>
  <pre><code>CoreException: Could not calculate build plan: Plugin org.apache.maven.plugins:maven-compiler-plugin:3.1 or one of its dependencies could not be resolved: Failed to read artifact descriptor for org.apache.maven.plugins:maven-compiler-plugin:jar:3.1: ArtifactResolutionException: org.apache.maven.plugins:maven-compiler-plugin:pom:3.1 failed to transfer from https://artifactory.xxx.dev/artifactory/clo-maven-dev during a previous attempt. This failure was cached in the local repository and resolution is not reattempted until the update interval of central has elapsed or updates are forced. Original error: Could not transfer artifact org.apache.maven.plugins:maven-compiler-plugin:pom:3.1 from/to central (https://artifactory.xxx.dev/artifactory/clo-maven-dev): Access denied to https://artifactory.xxx.dev/artifactory/clo-maven-dev/org/apache/maven/plugins/maven-compiler-plugin/3.1/maven-compiler-plugin-3.1.pom. Error code 403, 
  Failed to read artifact descriptor for junit:junit:jar:4.13.1
  ...
  ...
      at org.eclipse.core.internal.jobs.Worker.run(Worker.java:63)
  Caused by: org.eclipse.aether.resolution.ArtifactResolutionException: junit:junit:pom:4.13.1 failed to transfer from https://artifactory.xxx.dev/artifactory/clo-maven-dev during a previous attempt. This failure was cached in the local repository and resolution is not reattempted until the update interval of central has elapsed or updates are forced. Original error: Could not transfer artifact junit:junit:pom:4.13.1 from/to central (https://artifactory.xxx.dev/artifactory/clo-maven-dev): Access denied to https://artifactory.xxx.dev/artifactory/clo-maven-dev/junit/junit/4.13.1/junit-4.13.1.pom. Error code 401, 
  
  </code></pre>
  <pre><code>MD :mvn --quiet clean -f &quot;c:\Projects\jar-explorer-master\pom.xml&quot; &amp;&amp; mvn --quiet org.apache.maven.plugins:maven-dependency-plugin:3.0.2:tree -f &quot;c:\Projects\jar-explorer-master\pom.xml&quot; -DoutputFile=&quot;c:\Projects\jar-explorer-master\target\dependencies.txt&quot; -DoutputType=dot -DappendOutput=true
   STDOUT : [ERROR] Failed to execute goal org.apache.maven.plugins:maven-clean-plugin:2.5:clean (default-clean) on project jarexplorer: Execution default-clean of goal org.apache.maven.plugins:maven-clean-plugin:2.5:clean failed: Plugin org.apache.maven.plugins:maven-clean-plugin:2.5 or one of its dependencies could not be resolved: Failed to collect dependencies at org.apache.maven.plugins:maven-clean-plugin:jar:2.5 -&gt; org.codehaus.plexus:plexus-utils:jar:3.0: Failed to read artifact descriptor for org.codehaus.plexus:plexus-utils:jar:3.0: Could not transfer artifact org.codehaus.plexus:plexus-utils:pom:3.0 from/to central (https://artifactory.xxx.dev/artifactory/clo-maven-dev): authentication failed for https://artifactory.xxx.dev/artifactory/clo-maven-dev/org/codehaus/plexus/plexus-utils/3.0/plexus-utils-3.0.pom, status: 401 Unauthorized -&gt; [Help 1]
  [ERROR] 
  [ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
  [ERROR] Re-run Maven using the -X switch to enable full debug logging.
  [ERROR] 
  [ERROR] For more information about the errors and possible solutions, please read the following articles:
  [ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/PluginResolutionException
  </code></pre>
  <p>I then added the this line to POM.xml:</p>
  <pre><code>&lt;?xml version=&quot;1.0&quot; encoding=&quot;UTF-8&quot;?&gt;
  </code></pre>
  <p>... and opened the project using Eclipse, and execute the Maven Update Project, and the errors disappeared. I think there was some issue with authentication due to proxy issues. Now, I see only about 100 warnings, and I am able to build using vs code.</p>
  <p><a href="https://i.stack.imgur.com/NNdAd.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/NNdAd.png" alt="enter image description here" /></a></p>
  <p>I also noticed that the following file was added under <code>.settings</code> folder when I executed Update from Eclipse:</p>
  <pre><code>org.eclipse.jdt.core.prefs
  </code></pre>
  <p>How I can add the above file <code>org.eclipse.jdt.core.prefs</code> using vs code?</p>
  <p>How I can resolve the following warnings using vs code:</p>
  <pre><code>Build path specifies execution environment JavaSE-1.7. There are no JREs installed in the workspace that are strictly compatible with this environment.
  The compiler compliance specified is 1.7 but a JRE 1.8 is used
  </code></pre>