Text editor with syntax highlighting and line numbers?

Question

This is a bit challenging even probably for a team project, let alone for a one-man implementation, but I was trying to put together a simple yet elegant text editor with syntax highlighting, using a JEditorPane. I stumbled upon this which was discontinued and really hard for me to understand with all the lexer files and .lex stuff inside. I even found in some blog that this project was later taken on by some other team but even yet again discontinued. I don't need it to be too fancy, like having code folding and stuff (even though I am tempted to find out how to do this), but I need at least a basic syntax highlighting to exist and pretty much line numbers on the far left side just like Notepad++ for example. Keep in mind that I only need it to highlight Java source-code, at least for now.

What I am looking for is either a tutorial, a well-documented example and sample code, a pre-made package, even a tool for NetBeans can do the trick, I do not neccesarily need the source code written from scratch, I just need an implementation that can be of use. Thanks in advance!

P.S.This is not gonna be commercial or too big, don't ask why I want to reinvent the wheel when there are so many programming editors out there, I am learning and this came up as a nice exercise for me!

Answer 1

RSyntaxTextArea is BSD licensed and supports your requirements, plus code folding and more. Very simple to use.

Answer 2

Well I worked on a similar project and here's what I came up with. As far the line numbers go I used a scrollpane attached to the actual textpane. The scrollpane was then changing numbers with the following code:

public class LineNumberingTextArea extends JTextArea
{
private JTextPane textArea;


/**
 * This is the contructor that creates the LinNumbering TextArea.
 *
 * @param textArea The textArea that we will be modifying to add the 
 * line numbers to it.
 */
public LineNumberingTextArea(JTextPane textArea)
{
    this.textArea = textArea;
    setBackground(Color.BLACK);
    textArea.setFont(new Font("Consolas", Font.BOLD, 14));
    setEditable(false);
}

/**
 * This method will update the line numbers.
 */
public void updateLineNumbers()
{
    String lineNumbersText = getLineNumbersText();
    setText(lineNumbersText);
}


/**
 * This method will set the line numbers to show up on the JTextPane.
 *
 * @return This method will return a String which will be added to the 
 * the lineNumbering area in the JTextPane.
 */
private String getLineNumbersText()
{
    int counter = 0;
    int caretPosition = textArea.getDocument().getLength();
    Element root = textArea.getDocument().getDefaultRootElement();
    StringBuilder lineNumbersTextBuilder = new StringBuilder();
    lineNumbersTextBuilder.append("1").append(System.lineSeparator());

    for (int elementIndex = 2; elementIndex < root.getElementIndex(caretPosition) +2; 
        elementIndex++)
    {
        lineNumbersTextBuilder.append(elementIndex).append(System.lineSeparator());
    }
    return lineNumbersTextBuilder.toString();
}
}

The syntax highlighting is not an easy task, but what I started with was being able to search for strings based off some text files that contained all keywords for a certain language. Basically based off the extension of a file the function would find the correct file and look for words in that file that were contained within the text area.