包装类的自动包装和拆装

package day1_28;

import java.util.Scanner;
import java.util.Vector;

/**
 * Vector 向量集合类
 * 添加元素  addElement（Object obj）
 * 读取元素  Object elementAt(int index)
 */

public class ScoreTest {
    public static void main(String[] args) {
        ScoreTest st = new ScoreTest();
        st.score();
    }

    //不提示输入学生人数，按任意负数表示结束成绩输入
    public void score() {

        Scanner sc = new Scanner(System.in);
        Vector v = new Vector();
        int score;
        int maxScore = 0;
        for (; ; ) {
            System.out.print("请输入学生成绩(负数表示输入结束)：");
            score = sc.nextInt();
            if (score < 0) {
                break;
            }
            if (score > 100) {
                System.out.println("输入的数据非法，请重新输入");
                continue;
            }
            v.addElement(score);//自动装箱
            System.out.println();
            if (maxScore < score) {
                maxScore = score;
            }
        }

        System.out.println("最高分是：" + maxScore);

        char level;
        for (int i = 0; i < v.size(); i++) {
            Object obj = v.elementAt(i);
            score = (int)obj;//向下转型为Integer,然后自动拆箱
            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("学生" + (i + 1) + "的成绩是:" + score
                    + " 等级是" + level);
        }

    }
}