Split TextArea

Question

Im wanting to create a TextArea that will show ASCII on the left, and the Hex values on the right.
Im not sure where to start. Ive looked into the JTextArea source and noticed it doesnt have a paintComponent method. So obviosly text components render differently?
I thought of modifying the JTable, but I wont be dealing with rows.
I was then thinking of just implementing my own paintComponent for the text area, but I think I should learn how text components are drawn first.
Or, to save time, has anyone seen an implementation of this already?
Any ideas on where to start?

Answer 1

import java.awt.*;
import java.io.*;
import java.util.*;
import javax.swing.*;
import javax.swing.text.*;
public class ShowText extends JFrame{
    public ShowText(){
        setTitle("Show Text");
        setDefaultCloseOperation( EXIT_ON_CLOSE );
        try{
            readText();
        }catch(IOException ex){
            ex.printStackTrace();
        textPane = new JTextPane();
        textPane.setFont( new Font("monospaced", 0, 14) );
        JScrollPane scrollPane = new JScrollPane( textPane );
        getContentPane().add( scrollPane );
        showText(40);
        setScreenState(false);   //true = full screen
    private void showText(int textWidth){
        StringBuffer sb = new StringBuffer(1000);
        for ( int j=0; j<text.length(); j=j+textWidth ){
            int end = text.length();
            int end_2 = j+textWidth;
            if( end_2 > end ){
                text.append( blanks.substring( 0, end_2 - end ) );
            String str = text.substring(j, end_2);
            sb.append(str);
            sb.append("\t");
            sb.append(asciiToHex(str));
            sb.append("\n");
        setTabs( textPane, textWidth+5 );
        textPane.setText( sb.toString() );
    public void setTabs( final JTextPane textPane, int textWidth){
        FontMetrics fm = textPane.getFontMetrics( textPane.getFont() );
        int charWidth = fm.charWidth( 'W' );
        TabStop[] tabs = new TabStop[1];
        tabs[0] = new TabStop( textWidth * charWidth );
        TabSet tabSet = new TabSet(tabs);
        SimpleAttributeSet attributes = new SimpleAttributeSet();
        StyleConstants.setTabSet(attributes, tabSet);
        int length = textPane.getDocument().getLength();
        textPane.getStyledDocument().setParagraphAttributes(0, length, attributes, false);
    private void readText()throws IOException{
        BufferedReader reader = new BufferedReader(new FileReader("MyText.txt"));
        text = new StringBuffer(1000);
        for( String str = reader.readLine(); str != null; str = reader.readLine() ){
            text.append(str);
    private String asciiToHex(String ascii){
        StringBuilder hex = new StringBuilder();
        for (int i=0; i < ascii.length(); i++) {
            hex.append(Integer.toHexString(ascii.charAt(i)));
        return hex.toString();
    private void setScreenState(boolean full){
        setExtendedState(JFrame.MAXIMIZED_BOTH);
        if(full){
            setResizable(false);
            setVisible(true);
        }else{
            setVisible(true);
            setResizable(false);
    public static void main(final String[] args){
        new ShowText();
    private JTextPane textPane;
    private StringBuffer text;
    private final String blanks = "                                                  ";
}