1) @Eng.Fouad this was n_times mentioned (@camickr, @StanislavL) here for styled and highligted test use JTextComponent that supporting that
2) @Eng.Fouad you are right output from JTextArea

from code
import java.awt.*;
import javax.swing.*;
import javax.swing.text.*;
public class TextPaneHighlighting {
private static final long serialVersionUID = 1L;
private Highlighter.HighlightPainter cyanPainter;
private Highlighter.HighlightPainter redPainter;
public TextPaneHighlighting() {
JFrame frame = new JFrame();
JTextPane textPane = new JTextPane();
textPane.setText("one\ntwo\nthree\nfour\nfive\nsix\nseven\neight\n");
//textPane.setFont(new Font("Monospaced", Font.PLAIN, 12)); // uncommnent
JScrollPane scrollPane = new JScrollPane(textPane);
frame.add(scrollPane, BorderLayout.CENTER);// Highlight some text
cyanPainter = new DefaultHighlighter.DefaultHighlightPainter(Color.cyan);
redPainter = new DefaultHighlighter.DefaultHighlightPainter(Color.red);
try {
textPane.getHighlighter().addHighlight(0, 3, DefaultHighlighter.DefaultPainter);
textPane.getHighlighter().addHighlight(8, 14, cyanPainter);
textPane.getHighlighter().addHighlight(19, 24, redPainter);
} catch (BadLocationException ble) {
}
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setPreferredSize(new Dimension(300, 200));
frame.setLocationRelativeTo(null);
frame.pack();
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
JFrame.setDefaultLookAndFeelDecorated(true);
JDialog.setDefaultLookAndFeelDecorated(true);
try {
UIManager.setLookAndFeel(new org.pushingpixels.substance.api.skin.SubstanceBusinessBlackSteelLookAndFeel());
} catch (UnsupportedLookAndFeelException ex) {
}
TextPaneHighlighting tph = new TextPaneHighlighting();
}
});
}
}
3) as @ trashgod correctly mentioned never to set whatever in Substance without invokeLater, never, whatever Look and Feel sensitive, right maybe in this moment Font isn't important, maybe not
4) simple JTextArea have got some issue with Font and Look and Feel, maybe there are own Highlighter concept as for Renderer (sorry I lazy read API after wake_up) and Substance, for Renderer concept you must to use SubstanceRenderer instead of XxxRenderer, then all formatting wokrs as you excepted
import java.awt.*;
import javax.swing.*;
import javax.swing.text.*;
public class Fonts implements Runnable {
private String[] fnt;
private JFrame frm;
private JScrollPane jsp;
private JTextPane jta;
private int width = 450;
private int height = 300;
private GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
private StyledDocument doc;
private MutableAttributeSet mas;
private int cp = 0;
private Highlighter.HighlightPainter cyanPainter = new DefaultHighlighter.DefaultHighlightPainter(Color.cyan);
private Highlighter.HighlightPainter redPainter = new DefaultHighlighter.DefaultHighlightPainter(Color.red);
private Highlighter.HighlightPainter whitePainter = new DefaultHighlighter.DefaultHighlightPainter(Color.white);
private int _count = 0;
private int _lenght = 0;
public Fonts() {
jta = new JTextPane();
doc = jta.getStyledDocument();
jsp = new JScrollPane(jta);
jsp.setPreferredSize(new Dimension(height, width));
frm = new JFrame("awesome");
frm.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frm.setLayout(new BorderLayout());
frm.add(jsp, BorderLayout.CENTER);
frm.setLocation(100, 100);
frm.pack();
frm.setVisible(true);
jta.setCursor(Cursor.getPredefinedCursor(Cursor.WAIT_CURSOR));
fnt = ge.getAvailableFontFamilyNames();
mas = jta.getInputAttributes();
new Thread(this).start();
}
@Override
public void run() {
for (int i = 0; i < fnt.length; i++) {
StyleConstants.setBold(mas, false);
StyleConstants.setItalic(mas, false);
StyleConstants.setFontFamily(mas, fnt[i]);
StyleConstants.setFontSize(mas, 16);
dis(fnt[i]);
try {
Thread.sleep(75);
} catch (Exception e) {
e.printStackTrace();
}
StyleConstants.setBold(mas, true);
dis(fnt[i] + " Bold");
try {
Thread.sleep(75);
} catch (Exception e) {
e.printStackTrace();
}
StyleConstants.setItalic(mas, true);
dis(fnt[i] + " Bold & Italic");
try {
Thread.sleep(75);
} catch (Exception e) {
e.printStackTrace();
}
StyleConstants.setBold(mas, false);
dis(fnt[i] + " Italic");
try {
Thread.sleep(75);
} catch (Exception e) {
e.printStackTrace();
}
}
jta.setCursor(Cursor.getPredefinedCursor(Cursor.DEFAULT_CURSOR));
}
public void dis(String s) {
_count++;
_lenght = jta.getText().length();
try {
doc.insertString(cp, s, mas);
doc.insertString(cp, "\n", mas);
} catch (Exception bla_bla_bla_bla) {
bla_bla_bla_bla.printStackTrace();
}
if (_count % 2 == 0) {
try {
jta.getHighlighter().addHighlight(1, _lenght - 1, cyanPainter);
} catch (BadLocationException bla_bla_bla_bla) {
}
} else if (_count % 3 == 0) {
try {
jta.getHighlighter().addHighlight(1, _lenght - 1, redPainter);
} catch (BadLocationException bla_bla_bla_bla) {
}
} else {
try {
jta.getHighlighter().addHighlight(1, _lenght - 1, whitePainter);
} catch (BadLocationException bla_bla_bla_bla) {
}
}
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
JFrame.setDefaultLookAndFeelDecorated(true);
JDialog.setDefaultLookAndFeelDecorated(true);
try {
UIManager.setLookAndFeel(new org.pushingpixels.substance.api.skin.SubstanceBusinessBlackSteelLookAndFeel());
} catch (UnsupportedLookAndFeelException ex) {
}
Fonts fs = new Fonts();
}
});
}
}