To highlight all the text, use the selectAll() method of the JTextPane component −
JTextPane pane = new JTextPane(); pane.selectAll();
The following is an example to highlight the JTextPane text. Here, we are displaying a code in the JTextPane and highlighting it −
package my; import java.awt.BorderLayout; import java.awt.Container; import javax.swing.JFrame; import javax.swing.JScrollPane; import javax.swing.JTextPane; import javax.swing.text.BadLocationException; public class SwingDemo { public static void main(String args[]) throws BadLocationException { JFrame frame = new JFrame("Demo"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); Container container = frame.getContentPane(); JTextPane pane = new JTextPane(); pane.setContentType("text/html"); pane.setText("<HTML><BODY><CODE> #include <iostream>; <br> using namespace std; <br>main() {<br>cout << \"Hello World\";<br> return 0;<br>}</CODE><br></BODY></HTML>"); pane.selectAll(); JScrollPane scrollPane = new JScrollPane(pane); container.add(scrollPane, BorderLayout.CENTER); frame.setSize(550, 300); frame.setVisible(true); } }