Word of JTextArea don't change color [JAVA]

Question

I implemented this code, whose aim is to have a JtextArea that looks like an editor, in which some keywords change color when typed or insert. This is the code I wrote:

private void openBtnActionPerformed(java.awt.event.ActionEvent evt) {                                        
// TODO add your handling code here:
    chooser = new JFileChooser();
    FileNameExtensionFilter filter = new FileNameExtensionFilter(".txt files", "txt", "text");
    chooser.setFileFilter(filter);
    int option = chooser.showOpenDialog(null);
    if (option == JFileChooser.APPROVE_OPTION) {
    f = chooser.getSelectedFile();
    filename = f.getAbsolutePath();
    String modelSpec = readSpecification();
    spec = modelSpec;    

    final StyleContext cont = StyleContext.getDefaultStyleContext();
        final javax.swing.text.AttributeSet attrGray = cont.addAttribute(cont.getEmptySet(), StyleConstants.Foreground, Color.gray);
        final javax.swing.text.AttributeSet attrGreen = cont.addAttribute(cont.getEmptySet(), StyleConstants.Foreground, Color.GREEN);
        final javax.swing.text.AttributeSet attrBlue = cont.addAttribute(cont.getEmptySet(), StyleConstants.Foreground, Color.BLUE);
        final javax.swing.text.AttributeSet attrRed = cont.addAttribute(cont.getEmptySet(), StyleConstants.Foreground, Color.RED);
        final javax.swing.text.AttributeSet attrBlack = cont.addAttribute(cont.getEmptySet(), StyleConstants.Foreground, Color.BLACK);
        DefaultStyledDocument doc = new DefaultStyledDocument() {
                @Override
            public void insertString (int offset, String str, javax.swing.text.AttributeSet a) throws BadLocationException {
                super.insertString(offset, str, a);

                //String text = getText(0, getLength()-1);
                int before = findLastNonWordChar(spec, offset);
                if (before < 0) before = 0;
                int after = findFirstNonWordChar(spec, offset + str.length());
                int prevWord = before;
                int postWord = before;

                while (postWord <= after) {
                    if (postWord == after || String.valueOf(spec.charAt(postWord)).matches("\\W")) {                     

                        if (spec.substring(prevWord, postWord).matches("(\\W)*(System)"))
                            setCharacterAttributes(prevWord, postWord - prevWord, attrBlue, false);
                        else if (spec.substring(prevWord, postWord).matches("(\\W)*(PlasmaMembrane)"))
                            setCharacterAttributes(prevWord, postWord - prevWord, attrBlue, false);
                        else if (spec.substring(prevWord, postWord).matches("(\\W)*(Cytosol)"))
                            setCharacterAttributes(prevWord, postWord - prevWord, attrBlue, false);
                        else if (spec.substring(prevWord, postWord).matches("(\\W)*(Organelle)"))
                            setCharacterAttributes(prevWord, postWord - prevWord, attrBlue, false);
                        else if (spec.substring(prevWord, postWord).matches("(\\W)*(Nucleous)"))
                            setCharacterAttributes(prevWord, postWord - prevWord, attrBlue, false);
                        else if (spec.substring(prevWord, postWord).matches("(\\W)*(volume)"))
                            setCharacterAttributes(prevWord, postWord - prevWord, attrGray, false);
                        else if (spec.substring(prevWord, postWord).matches("(\\W)*(rate)"))
                            setCharacterAttributes(prevWord, postWord - prevWord, attrRed, false); 

                        else
                            setCharacterAttributes(prevWord, postWord - prevWord, attrBlack, false);
                        prevWord = postWord;
                    }
                    postWord++;
                }
            }

                @Override
            public void remove (int offs, int len) throws BadLocationException {
                super.remove(offs, len);

                String text = getText(0, getLength());
                int before = findLastNonWordChar(text, offs);
                if (before < 0) before = 0;
                int after = findFirstNonWordChar(text, offs);

                if (text.substring(before, after).matches("(\\W)*(System)")) 
                    setCharacterAttributes(before, after - before, attrBlue, false);
                else if (text.substring(before, after).matches("(\\W)*(PlasmaMembrane)")) 
                    setCharacterAttributes(before, after - before, attrBlue, false);   
                else if (text.substring(before, after).matches("(\\W)*(Cytosol)")) 
                    setCharacterAttributes(before, after - before, attrBlue, false);   
                else if (text.substring(before, after).matches("(\\W)*(Organelle)")) 
                    setCharacterAttributes(before, after - before, attrBlue, false);   
                else if (text.substring(before, after).matches("(\\W)*(Nucleous)")) 
                    setCharacterAttributes(before, after - before, attrBlue, false);   
                else if (text.substring(before, after).matches("(\\W)*(volume)")) 
                    setCharacterAttributes(before, after - before, attrGray, false);
                else if (text.substring(before, after).matches("(\\W)*(rate)")) 
                    setCharacterAttributes(before, after - before, attrRed, false);   
                 else {
                    setCharacterAttributes(before, after - before, attrBlack, false);
                }
            } 
        }; 


    textModel.setText(spec);




    }
}                                       

There are no errors or Excpetions caught, but none of those words change the foreground color. Why this code doesn't do anything? Thanks for helping

Answer 1

Why this code doesn't do anything?

A JTextArea doesn't support attributes. All the text must be a single color. The attributes are ignored by the PlainDocument.

You need to use a JTextPane which uses a StyledDocument which does support the attributes.

See the section from the Swing tutorial on Text Component Features for a working example of a text pane that support different attributes.