title: Is it possible to call constructor on existing instance?
body: <p>It is known that using <code>sun.misc.Unsafe#allocateInstance</code> one can create an object without calling any class constructors.</p>
  
  <p>Is it possible to do the opposite: given an existing instance, invoke a constructor on it?</p>
  
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  <p><strong>Clarification</strong>: this is not the question about something I'd do in production code. I'm curious about JVM internals and crazy things that can still be done. Answers specific to some JVM version are welcome.</p>