Few Questions about org.w3c.dom.Element

In that org.w3c.dom.Element interface

I can getTagName()
But
1) How do I do know is it an empty tag or not?

<tag ..... />

2) How do I know when will be a close tag?

<tag1>
<tag2>xxxx</tag2>
<tag3 ..... />
<tag4 ..... />xxxxx</tag4>
.......
</tag1>

Thank Q very much in advance!