Java Programming

Hello I have an xml file , and I read all Elements of this file using xml parser as follow:

public void readXmlFile(){
        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
	 DocumentBuilder builder = factory.newDocumentBuilder();
	 Document doc = builder.parse(filePath);
	System.out.println(builder.parse(filePath).getAttributes());
	NodeList list = doc.getElementsByTagName("*");
        ....
}

if I have the following xml file I can read it with out any problem:

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<employee>
    <person id=1>
            <name>john</name>
            <lastname>logan</logan>
    </person>
</employee>

but if i have my xml file empty means only with the xml header :

<?xml version="1.0" encoding="UTF-8" standalone="no"?>

Then when it comes over this method it fails and gives me this error: *[Fatal Error] file.xml:2:1: Premature end of file.*
because there is no element in the file.
The question is how can i check the content of my xml file to be not empty before parsing?