If we stick to method akin to dom childNodes() method where in JDom2 it would read as children() method, you have to successively go deeper in level. In this case, go twice in depth. This is how you can do that.
In a sense, you can do it more directly without explicitly spelling out the detail of traversing level-by-level... In dom there is getElementsByTagName() method and there is also xpath as a derivative technology. In JDom2, it takes form in Filter class and its sub-classes. This is how you can proceed with the ElementFilter.
Now you have two methods to do it.
Catch Ernie! Catch the egg! And catch this tiny ad too: