Main.java Source code

Introduction

Here is the source code for Main.java

Source

import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.text.AbstractDocument;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.Document;
import javax.swing.text.DocumentFilter;
import javax.swing.text.Element;

public class Main {
    public static void main(String[] args) {
        JTextArea textArea = new JTextArea(10, 30);
        AbstractDocument doc = (AbstractDocument) textArea.getDocument();
        doc.setDocumentFilter(new EndOfLineFilter());

        JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add(new JScrollPane(textArea));
        frame.pack();
        frame.setVisible(true);
    }
}

class EndOfLineFilter extends DocumentFilter {
    @Override
    public void replace(FilterBypass fb, final int offset, int length, String text, AttributeSet a)
            throws BadLocationException {
        if (text.equals("\n")) {
            text = addWhiteSpace(fb, offset, text);
        }
        super.replace(fb, offset, length, text, a);
    }

    private String addWhiteSpace(FilterBypass fb, int offset, String text) throws BadLocationException {
        Document doc = fb.getDocument();
        Element root = doc.getDefaultRootElement();
        int line = root.getElementIndex(offset);
        int i = root.getElement(line).getStartOffset();
        StringBuilder whiteSpace = new StringBuilder(text);

        while (true) {
            String temp = doc.getText(i, 1);
            if (temp.equals(" ") || temp.equals("\t")) {
                System.out.println("added");
                whiteSpace.append(temp);
                i++;
            } else {
                break;
            }
        }
        return whiteSpace.toString();
    }
}