包装类实验代码：
public class ScoreTest {
public static void main(String[] args) {
int maxscore = 0;
//实例化Scanner，从键盘获取学生信息
Scanner scan = new Scanner(System.in);
//创建Vector对象，Vector v = new Vector（）；
Vector v = new Vector();
//用循环添加数组
for(;;) {
System.out.println("请输入学生成绩：（输入负数停止输入）");
int score = scan.nextInt();
if(score<0) {
break;
}
Integer inScore = score;
v.addElement(inScore);//添加操作 v.addElement(Object obj)
if(maxscore < score) {
maxscore = score;
}//最大值
}
//遍历获得学生等级
char level;
for(int i=0;i<v.size();i++) {
Object obj = v.elementAt(i);
Integer inscore = (Integer)obj;
int score = inscore;
if(maxscore - score<=10) {
level = 'A';
}
else if(maxscore - score<=20) {
level = 'B';
}
else if(maxscore - score<=30) {
level = 'C';
}
else {
level = 'D';
}
System.out.println("成绩："+score +" " + "等级"+level);
}
}
}