title: -XX:+UseConcMarkSweepGC (what is default young generation collector?)
body: <p>As far as I know we can run JVM with the next options:</p>
  
  <pre><code>-XX:+UseConcMarkSweepGC
  -XX:-UseParNewGC
  </code></pre>
  
  <p>in this case we will have the <strong>Serial (DefNew)</strong> garbage collector for the young generation and the <strong>Concurrent Mark Sweep</strong> garbage collector for the old generation.</p>
  
  <p>Well, can we run JVM with <code>-XX:+UseConcMarkSweepGC</code> option only? I mean without any options that describes a garbage collector for the young generation. If we can do that, which garbage collector will be used for the old generation?</p>