title: Sensu check for jvm heap not working
body: <p>I am facing issues with sensu-plugins-java. I have installed plugin in our server and I need to use check-java-heap-pcnt.rb to monitor the heap size in our server, but it is not showing proper output when I try to run the check locally. 
  Here's how I tried to run the check locally: </p>
  
  <pre><code># ./check-java-heap-pcnt.rb -n java -w 70 -c 85 -j /usr/java/defaults/bin/ -p
  </code></pre>
  
  <p>Here's the output it generated: </p>
  
  <pre><code>    invalid argument count
  Usage: jstat -help|-options
         jstat -&lt;option&gt; [-t] [-h&lt;lines&gt;] &lt;vmid&gt; [&lt;interval&gt; [&lt;count&gt;]]
  
  Definitions:
    &lt;option&gt;      An option reported by the -options option
    &lt;vmid&gt;        Virtual Machine Identifier. A vmid takes the following form:
                       &lt;lvmid&gt;[@&lt;hostname&gt;[:&lt;port&gt;]]
                  Where &lt;lvmid&gt; is the local vm identifier for the target
                  Java virtual machine, typically a process id; &lt;hostname&gt;is
                  the name of the host running the target Java virtual machine;
                  and &lt;port&gt; is the port number for the rmiregistry on the
                  target host. See the jvmstat documentation for a more complete
                  description of the Virtual Machine Identifier.
    &lt;lines&gt;       Number of samples between header lines.
    &lt;interval&gt;    Sampling interval. The following forms are allowed:
                      &lt;n&gt;["ms"|"s"]
                  Where &lt;n&gt; is an integer and the suffix specifies the units as 
                  milliseconds("ms") or seconds("s"). The default units are "ms".
    &lt;count&gt;       Number of samples to take before terminating.
    -J&lt;flag&gt;      Pass &lt;flag&gt; directly to the runtime system. 
  (standard_in) 1: syntax error 
  MEM UNKNOWN -
  </code></pre>