问 缓存BufferedImage时可能出现内存泄漏

EN

class Provider {
    @Override
    public IData render(String... layers,String coordinate) {
        int rwidth = 256 , rheight = 256 ;
        ArrayList<BufferedImage> result = new ArrayList<BufferedImage>();
        for (String layer : layers) {
            String lkey = layer + "-" + coordinate;
            BufferedImage imageData = cacher.get(lkey);
            if (imageData == null) {
                try {
                    imageData = generateImage(layer, coordinate,rwidth, rheight, bbox);
                    cacher.put(lkey, imageData);
                } catch (IOException e) {
                    e.printStackTrace();
                    continue;
            if (imageData != null) {
                result.add(imageData);
        return new Data(rheight, rheight, width, result);
    private BufferedImage generateImage(String layer, String coordinate,int rwidth, int rheight) throws IOException {
        BufferedImage image = new BufferedImage(rwidth, rheight, BufferedImage.TYPE_INT_ARGB);
        Graphics2D g = image.createGraphics();
        g.setColor(Color.RED);
        g.drawString(layer+"-"+coordinate, new Random().nextInt(rwidth), new Random().nextInt(rheight));
        g.dispose();
        return image;
class Data implements IData {
    public Data(int imageWidth, int imageHeight, int originalWidth, ArrayList<BufferedImage> images) {
        this.imageResult = new BufferedImage(this.imageWidth, this.imageHeight, BufferedImage.TYPE_INT_ARGB);
        Graphics2D g = imageResult.createGraphics();
        for (BufferedImage imgData : images) {
            g.drawImage(imgData, 0, 0, null);
            imgData = null;
        imageResult.flush();
        g.dispose();
        images.clear();
    @Override
    public void save(OutputStream out, String format) throws IOException {
        ImageIO.write(this.imageResult, format, out);
        out.flush();
        this.imageResult = null;
}

class ImageServlet  extends HttpServlet {
    void doGet(req,res){
        IData data= provider.render(req.getParameter("layers").split(","));
        OutputStream out=res.getOutputStream();
        data.save(out,"png")
        out.flush();