Java Vector 二分查找

import java.util.Collections;
import java.util.Vector;

public class Main {
   public static void main(String[] args) {
      Vector<String> v = new Vector<String>();
      v.add("X");
      v.add("M");
      v.add("D");
      v.add("A");
      v.add("O");
      Collections.sort(v);
      System.out.println(v);
      int index = Collections.binarySearch(v, "D");
      System.out.println("Element found at : " + index);
   }
}