This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
If the content is large and you're worried about essentially doubling its RAM footprint, then you might want to look into yourTextArea.getDocument().getText(offset, length, yourSegment). That doesn't help you go line by line, but it can minimize copying the text.