过路大神帮忙看一下这个Java程序需要哪些API

[weixin_44821374]

public class PhotoAlbum extends Applet { private Choice myChoice; // 声明Choice对象 private String[] myString1, myString2; // 声明String类型的数组 private int totalPics; // 声明一个int型变量 private Image offI; // 声明Image对象 private Image[] img; // 声明一组Image对象数组 private Graphics offG; // 声明一个Graphics对象 private MediaTracker imagetracker; // 声明一个MediaTracker对象 public void init() { // 对Applet小程序进行初始化 this.setSize(600, 450); this.setLayout(null); myChoice = new Choice(); myChoice.setBounds(10, 10, 290, 20); totalPics = 8; myString1 = new String[totalPics]; myString2 = new String[totalPics]; img = new Image[totalPics]; for (int i = 0; i ＜ totalPics; i++) { myString1[i] = new String(""); myString2[i] = new String(""); } String s = new String(""); imagetracker = new MediaTracker(this); // 加载图片 for (int i = 0; i ＜ totalPics; i++) { s = "第 " + (i + 1) + " 张照片"; myString1[i] = s; System.out.println(myString1[i]); myChoice.addItem(s); // 向下拉列表中增加选项 s = (i + 1) + ".jpg"; myString2[i] = s; img[i] = getImage(getDocumentBase(), s); imagetracker.addImage(img[i], 0); } try { imagetracker.waitForID(0); } catch (InterruptedException e) { } add(myChoice); offI = createImage(getSize().width, getSize().height - 40);// 创建图像 offG = offI.getGraphics(); offI = img[0]; offG.drawImage(offI, 0, 0, this); repaint(); } public void paint(Graphics g) { g.drawImage(offI, 10, 40, this); } // 使用action()方法来获得Java Applet小程序运行时所发生的事件 public boolean action(Event e, Object o) { if (e.target == myChoice) { String s = new String(""); offG.setColor(this.getBackground()); offG.fillRect(0, 40, getSize().width, getSize().height - 40); offI = img[myChoice.getSelectedIndex()]; offG.drawImage(offI, 0, 0, this); repaint(); } return true; } }