JAXP and the associated XML APIs:

JAXP: Java API for XML Processing
JAXB: Java Architecture for XML Binding
JDOM: Java DOM
DOM4J
JAXM: Java API for XML Messaging
JAX-RPC: Java API for XML-based Remote Process Communications
JAXR: Java API for XML Registries

The JAXP APIs:

javax.xml.parsers: The JAXP APIs, which provide a common interface for different vendors’ SAX and DOM parsers.

org.w3c.dom: Defines the Document class (a DOM), as well as classes for all of the components of a DOM.

org.xml.sax: Defines the basic SAX APIs.

javax.xml.transform: Defines the XSLT APIs that let you transform XML into other forms.