Working with DOM

Problem:   Print the <students> element count of this XML file:

   <?xml version="1.0"?> 
   <course>
      <name id="csci_2962">Programming XML in Java</name>
      <teacher id="jp">
         <name>John Punin</name>
      </teacher>
      <student id="js">
         <name>John Smith</name>
         <hw1>30</hw1>
         <hw2>70</hw2>
         <project>80</project>
         <final>85</final>
      </student>
      <student id="gl">
         <name>George Lucas</name>
         <hw1>80</hw1>
         <hw2>90</hw2>
         <project>100</project>
         <final>40</final>
      </student>
      <student id="lr">
         <name>Elizabeth Roberts</name>
         <hw1>60</hw1>
         <hw2>95</hw2>
         <project>50</project>
         <final>90</final>
      </student>
   </course>