//演示Vector類的用法。 
import java.util.*;
import javax.swing.JOptionPane;
public class UsingVector {
  public static void main(String args[]) {

	 Vector scoreVector = new Vector();//用矢量存儲分數
	 double bestScore=0;
	 char grade; //定義分數的級別

	 do{
		//讀入分數并找出最高分
		String scoreString = JOptionPane.showInputDialog(null,
			"請輸入分數" +
			"\n輸入負數表示輸入結束","演示Vector(輸入)",
			JOptionPane.QUESTION_MESSAGE);
		//將字符串轉換成整型值
		double scoreInt = Integer.parseInt(scoreString);
		if (scoreInt<0)
		{
			break;
		}
		//將分數添加進矢量
		scoreVector.addElement(new Double(scoreInt));
		//找出最高分
		if (scoreInt > bestScore)
		{
			bestScore = scoreInt;
		}
	 }while (true);

	 //設置輸出字符串
	 String output = "一共有"+scoreVector.size() +"個學生";
	 //確定并顯示分數的級別
	 for (int i = 0;i < scoreVector.size() ; i++)
	 {
		 //檢索矢量
		 Double doubleObj = (Double)(scoreVector.elementAt(i));
		 //獲取分數
		 double score = doubleObj.doubleValue();
		 if(score >= bestScore-10)
			 grade = 'A';
		 else if(score >=bestScore-20)
			 grade = 'B';
		 else if(score >=bestScore-30)
			 grade = 'C';
		 else
			 grade = 'D';
		 output += "\n學生"+ i +"的分數是"+ score +
			 "，級別是" + grade;
	 }

	 JOptionPane.showMessageDialog(null,output,
		 "演示Vector(輸出)",JOptionPane.INFORMATION_MESSAGE);
	 System.exit(0);
  }
}