Centering Text in a JTextArea or JTextPane – Horizontal Text Alignment

You need to use a JTextPane and use attributes. The following should center all the text:

StyledDocument doc = textPane.getStyledDocument();
SimpleAttributeSet center = new SimpleAttributeSet();
StyleConstants.setAlignment(center, StyleConstants.ALIGN_CENTER);
doc.setParagraphAttributes(0, doc.getLength(), center, false);

Edit:

Vertical centering is not supported as far as I know. Here is some code you might find useful: Vertical Alignment of JTextPane