Extracting child elements of an XML in Java

I have a requirement where I have to extract parts of XML child nodes and use it to generate reports.

Here is an example of the sample XML code :

<A>
 <B>
  <C>
   <D>
   </D>
   <D>
   </D>
  </C>
 </B>
 <B>
  <C>
   <D>
   </D>
  </C>
 </B>
 <B>
  <C>
  </C>
 </B>
</A>

I want to extract all the elements with B as XML tag name and use that to create reports. Could someone please explain how we can extract all the elements .

PS: These extracted elements should also have their child elements in it.