Anyone know how to make an "Index Transparent" gif

Question

I have successfully made transparent PNGs and GIFusing an Alpha transparency but now I need to make images which would be the same as ueing fireworks / Photoshop to make a colour transparent. i.e. indexed transparency.
Does anyone know how to do this.
My code is as follows :
// configure all of the parameters
String text = "ABC abc XYZ xyz ["+ new Date()+"]";
String font_file = "./tst/Maiandb.TTF";
font_file = request.getRealPath(font_file);
float size = 30.0f;
Color background = Color.white;
Color color = Color.black;
Font font = Font.createFont(Font.TRUETYPE_FONT, new FileInputStream(font_file));
font = font.deriveFont(size);
buffer = new java.awt.image.BufferedImage(1,1,java.awt.image.BufferedImage.TYPE_INT_RGB);
Graphics2D g2 = buffer.createGraphics();
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
java.awt.font.FontRenderContext fc = g2.getFontRenderContext();
java.awt.geom.Rectangle2D bounds = font.getStringBounds(text,fc);
// calculate the size of the text
width = (int) bounds.getWidth();
height = (int) bounds.getHeight();
// prepare some output
buffer = new java.awt.image.BufferedImage(width, height, java.awt.image.BufferedImage.TYPE_INT_ARGB);
g2 = buffer.createGraphics();
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2.setRenderingHint(RenderingHints.KEY_ALPHA_INTERPOLATION, RenderingHints.VALUE_ALPHA_INTERPOLATION_QUALITY);
g2.setFont(font);
// actually do the drawing
Color transparent = new Color(0, 0, 0, 0);
g2.setColor(transparent);
g2.fillRect(0,0,width,height);
g2.setColor(color);
g2.setComposite(AlphaComposite.SrcOver);
g2.drawString(text,0,(int)-bounds.getY());
File file = new File ("./jsp1/tst/fred1.gif");
com.gif4j.light.GifImage gifImage = new com.gif4j.light.GifImage();
com.gif4j.light.GifFrame gifFrame = new com.gif4j.light.GifFrame(buffer);
gifImage.addGifFrame(gifFrame);
GifEncoder.encode(gifImage, file);Thanks in advance

Answer 1

^^EDIT^^
System admins updated iMac to OS X Mountain Lion (10.8.4).