分析下列程序，写出其功能。 import java.applet.*; import java.awt.*; import java.awt.event.*; public class Test extends Applet implements MouseListener { final int number = 5; int count = 0; Image[] card = new Image[number]; public void init() { setSize(1200,1000); addMouseListener(this); for (int i = 0; i < number; i++) { card[i] = getImage(getCodeBase(), i+".jpg"); } } public void paint(Graphics g) { if ((card[count]) != null) g.drawImage(card[count], 10,10,card[count].getWidth(this),card[count].getHeight(this), this); } public void mousePressed(MouseEvent e) { count = (count + 1) % number; repaint(); } public void mouseReleased(MouseEvent e) {} public void mouseEntered(MouseEvent e) {} public void mouseExited(MouseEvent e) {} public void mouseClicked(MouseEvent e) {} }