Java Code:
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.Shape;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionAdapter;
import java.awt.font.FontRenderContext;
import java.awt.font.TextHitInfo;
import java.awt.font.TextLayout;
import java.awt.geom.AffineTransform;

import javax.swing.JFrame;
import javax.swing.JPanel;

public class Highlights extends JPanel {
  private TextLayout textLayout;

  private TextHitInfo firstHit, secondHit;

  private int x = 40, y = 80;

    public Highlights(){
    addMouseListener(new MouseAdapter() {
      public void mousePressed(MouseEvent me) {
        firstHit = textLayout.hitTestChar(me.getX() - x, me.getY()
            - y);
        secondHit = null;
      }

      public void mouseReleased(MouseEvent me) {
        secondHit = textLayout.hitTestChar(me.getX() - x, me.getY()
            - y);
        repaint();
      }
    });
    addMouseMotionListener(new MouseMotionAdapter() {
      public void mouseDragged(MouseEvent me) {
        secondHit = textLayout.hitTestChar(me.getX() - x, me.getY()
            - y);
        repaint();
      }
    });
    }
  public void paint(Graphics g) {
    Graphics2D g2 = (Graphics2D) g;

    g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
        RenderingHints.VALUE_ANTIALIAS_ON);
    g2.setRenderingHint(RenderingHints.KEY_FRACTIONALMETRICS,
        RenderingHints.VALUE_FRACTIONALMETRICS_ON);

    String s = "Drag the text to highlight Java Source and Support.";
    Font font = new Font("Serif", Font.PLAIN, 32);

    if (textLayout == null) {
      FontRenderContext frc = g2.getFontRenderContext();
      textLayout = new TextLayout(s, font, frc);
    }

    // Draw the highlight.
    if (firstHit != null && secondHit != null) {
      Shape base = textLayout.getLogicalHighlightShape(firstHit
          .getInsertionIndex(), secondHit.getInsertionIndex());
      AffineTransform at = AffineTransform.getTranslateInstance(x, y);
      Shape highlight = at.createTransformedShape(base);
      g2.setPaint(Color.white);
      g2.fill(highlight);
    }

    g2.setPaint(Color.black);
    textLayout.draw(g2, x, y);
  }
  public static void main(String[] args) {
    JFrame f = new JFrame();
    f.getContentPane().add(new Highlights());
    f.setSize(850, 250);
    f.show();

  }
}