网上抄的一个截图工具，在哪里没有释放内存呢？为什么每次截图，内存都涨一大截？

Question

package com;

import java.io.*;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import java.time.LocalDateTime;
import javax.imageio.*;

/**
 * 一个简单的屏幕抓图
 **/
public class Demo extends KeyAdapter {

    private static Boolean ENTER = false;

    public static void main(String[] args) throws Exception {
//        String userdir = System.getProperty("user.dir");
//        while (true){
            JFrame parent = new JFrame("截图工具");
            parent.setSize(120,50);
            Button bt = new Button("");
            parent.add(bt);
            // 监听事件
            bt.addKeyListener(new KeyAdapter() {
                /**
                 * Invoked when a key has been pressed.
                 *
                 * @param e
                 */
                @Override
                public void keyPressed(KeyEvent e) {
                    super.keyPressed(e);
                    if(e.getKeyCode()== KeyEvent.VK_F2){
                        try{
                            screenshot();
                        }catch (Exception l){
                            l.printStackTrace();
                        }

                    }
                }
            });
            // 用户不可以调整该窗体的大小
            parent.setResizable(false);
            // 始终保持窗体在最前面transferHandler = null
            parent.setAlwaysOnTop(true);
            // 关闭窗体，停止程序运行
            parent.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            parent.setVisible(true);
//            while(parent.isDisplayable()){
//
//            }
//        }
    }

    private static void screenshot() throws Exception{
//        File tempFile = new File("C:\\Users\\zt\\Desktop\\牛逼哄哄能量瓶小伙", LocalDateTime.now().toString() + ".png");
        Demo capture = Demo.getInstance();
        capture.captureImage();
        JFrame frame = new JFrame("");
        JPanel panel = new JPanel();
        panel.setLayout(new BorderLayout());
        JLabel imagebox = new JLabel();
        panel.add(BorderLayout.CENTER, imagebox);
        imagebox.setIcon(capture.getPickedIcon());
//        capture.saveToFile(tempFile);

        capture.captureImage();
        imagebox.setIcon(capture.getPickedIcon());
        frame.setContentPane(panel);
        frame.addWindowListener(new WindowAdapter(){
            @Override
            public void windowClosing(WindowEvent e){
                frame.remove(panel);
                frame.remove(imagebox);
            }
        });
        frame.setSize(capture.recW, capture.recH);
        frame.setVisible(true);
        frame.setAlwaysOnTop(true);
    }

    private Demo() {
        try {
            robot = new Robot();

        } catch (AWTException e) {
            System.err.println("Internal Error: " + e);
            e.printStackTrace();
        }
        JPanel cp = (JPanel) dialog.getContentPane();
        cp.setLayout(new BorderLayout());
        labFullScreenImage.addMouseListener(new MouseAdapter() {
            @Override
            public void mouseReleased(MouseEvent evn) {
                isFirstPoint = true;
                pickedImage = fullScreenImage.getSubimage(recX, recY, recW,
                        recH);
                dialog.setVisible(false);

            }

        });

        labFullScreenImage.addMouseMotionListener(new MouseMotionAdapter() {
            @Override
            public void mouseDragged(MouseEvent evn) {
                if (isFirstPoint) {
                    x1 = evn.getX();
                    y1 = evn.getY();
                    isFirstPoint = false;
                } else {
                    x2 = evn.getX();
                    y2 = evn.getY();
                    int maxX = Math.max(x1, x2);
                    int maxY = Math.max(y1, y2);
                    int minX = Math.min(x1, x2);
                    int minY = Math.min(y1, y2);
                    recX = minX;
                    recY = minY;
                    recW = maxX - minX;
                    recH = maxY - minY;
                    labFullScreenImage.drawRectangle(recX, recY, recW, recH);
                }
            }
            @Override
            public void mouseMoved(MouseEvent e) {
                labFullScreenImage.drawCross(e.getX(), e.getY());
            }
        });
        cp.add(BorderLayout.CENTER, labFullScreenImage);
        dialog.setCursor(Cursor.getPredefinedCursor(Cursor.CROSSHAIR_CURSOR));
        dialog.setAlwaysOnTop(true);
        dialog.setMaximumSize(Toolkit.getDefaultToolkit().getScreenSize());
        dialog.setUndecorated(true);
        dialog.setSize(dialog.getMaximumSize());
        dialog.setModal(true);

    }
// Singleton Pattern
    public static Demo getInstance() {
        return defaultCapturer;
    }
    /**
     * 捕捉全屏慕
     */
    public Icon captureFullScreen() {
        fullScreenImage = robot.createScreenCapture(new Rectangle(Toolkit

                .getDefaultToolkit().getScreenSize()));
        ImageIcon icon = new ImageIcon(fullScreenImage);
        return icon;
    }
    /**
     * 捕捉屏幕的一个矫形区域
     */
    public void captureImage() {
        fullScreenImage = robot.createScreenCapture(new Rectangle(Toolkit.getDefaultToolkit().getScreenSize()));
        ImageIcon icon = new ImageIcon(fullScreenImage);
        labFullScreenImage.setIcon(icon);
        dialog.setVisible(true);
    }
    /**
     * 得到捕捉后的BufferedImage
     */
    public BufferedImage getPickedImage() {
        return pickedImage;
    }
    /**
     * 得到捕捉后的Icon
     */
    public ImageIcon getPickedIcon() {
        return new ImageIcon(getPickedImage());
    }
    /**
     * 储存为一个文件,为PNG格式
     *
     * @deprecated replaced by saveAsPNG(File file)
     **/
    @Deprecated
    public void saveToFile(File file) throws IOException {
        ImageIO.write(getPickedImage(), defaultImageFormater, file);

    }
    /**
     * 储存为一个文件,为PNG格式
     */
    public void saveAsPNG(File file) throws IOException {
        ImageIO.write(getPickedImage(), "png", file);

    }
    /**
     * 储存为一个JPEG格式图像文件
     */
    public void saveAsJPEG(File file) throws IOException {
        ImageIO.write(getPickedImage(), "JPEG", file);

    }
    /**
     * 写入一个OutputStream
     */
    public void write(OutputStream out) throws IOException {
        ImageIO.write(getPickedImage(), defaultImageFormater, out);

    }
// singleton design pattern
    private static Demo defaultCapturer = new Demo();
    private int x1, y1, x2, y2;
    private int recX, recY, recH, recW;// 截取的图像
    private boolean isFirstPoint = true;
    private BackgroundImage labFullScreenImage = new BackgroundImage();
    private Robot robot;
    private BufferedImage fullScreenImage;
    private BufferedImage pickedImage;
    private String defaultImageFormater = "png";
    private JDialog dialog = new JDialog();
}

/**
 * 显示图片的Label
 */

class BackgroundImage extends JLabel {
    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.drawRect(x, y, w, h);
        String area = Integer.toString(w) + " * " + Integer.toString(h);
        g.drawString(area, x + (int) w / 2 - 15, y + (int) h / 2);
        g.drawLine(lineX, 0, lineX, getHeight());
        g.drawLine(0, lineY, getWidth(), lineY);
    }

    public void drawRectangle(int x, int y, int width, int height) {
        this.x = x;
        this.y = y;
        h = height;
        w = width;
        repaint();
    }

    public void drawCross(int x, int y) {
        lineX = x;
        lineY = y;
        repaint();
    }
    int lineX,lineY;
    int x,y,h,w;

}