Creating and Modifying XML Documents - Beginning Java 2 SDK - page 1059

There's an alternative approach that provides a bit more flexibility but it is not quite so direct. You first
call the getDOMImplementation() method for the DocumentBuilder object:

DOMImplementation domImpl = builder.getDOMImplementation();

This returns a reference of type DOMImplementation to an object that encapsulates the underlying
DOM implementation. This interface type is defined in the org.w3c.dom package.

There are three methods you can call for a DOMImplementation object:

createDocument( Creates a Document object with the root element having

the name qualifiedName that is defined in the
namespace specified by namespaceURI . The third
argument specifies the DOCTYPE node to be added to the
document. If you don't want to declare a DOCTYPE , then
doctype can be specified as null .

String namespaceURI,
String qualifiedName,

DocumentType doctype)

This method will throw an exception of type
DOMException if the second argument is incorrect in some
way.

createDocumentType(

Creates a node of type DocumentType that represents a
DOCTYPE declaration. The first argument is the qualified
name of the root element, the second argument is the public
ID of the external subset of the DTD, and the third
argument is its system ID. This method will also throw an
exception of type DOMException if the first argument
contains an illegal character or is not of the correct form.

String qualifiedName,
String publicID,

String systemID)

hasFeature(String feature,
String version)

Returns true if the DOM implementation has the feature
with the name feature . The second argument specifies the
DOM version number of the feature and can be either
"1.0" or "2.0" with DOM level 2.

You can see from the first two methods here that there is a big advantage to using a
DOMImplementation object to create a document. First of all, you can create a DocumentType
object by calling the createDocumentType() method:

DocumentType doctype = null;
try {
doctype = domImpl.createDocumentType("sketch", null, "sketcher.dtd");

} catch(DOMException e) {
// Handle the exception
}

This code fragment creates a DocumentType node for an external DOCTYPE declaration with the name
sketch , with the system ID sketcher.dtd . There is no public ID in this case since we specified the
second argument as null . You can now use the DocumentType object in the creation of a document: