DevOps, CI/CD and Automation

I've been asked to convert text in a flat file to an XML document. The XML document must conform to an XML schema. Currenlty, there is no requirement to store the resulting xml in the database.

Therefore my approach will be:
1. parse the flat file and store the contents in an array (the flat file and target xml is fairly simple in structure)
2. Transfer the contents of the array to the xml structure
3. validate the xml against the schema

I'm new to Java. Therefore, what classes should I be using to assist in step 2. Obvoiusly, I dont want to have to write my own implementation from scratch (i.e. a method to build an element, method to escape reserved characters etc).

Could you please suggest classes that cover both DOM and SAX API's.

I'm working with a 9.2.0.4 database and XDK.

Thanks