java利用 list隨機抽取元素

/**
   * 從list中隨機抽取元素
   *
   * @param list
   * @param n
   * @return void
   * @throws
   * @Title: createRandomList
   * @Description: TODO
   */
  private static List createRandomList(List list, int n) {
    // TODO Auto-generated method stub
    Map map = new HashMap();
    List listNew = new ArrayList();
    if (list.size() <= n) {
      return list;
    } else {
      while (map.size() < n) {
        int random = (int) (Math.random() * list.size());
        if (!map.containsKey(random)) {
          map.put(random, "");
          System.out.println(random + "===========" + list.get(random));
          listNew.add(list.get(random));
        }
      }
      return listNew;
    }
  }

List<String> list = new ArrayList<String>();
    list.add("mjb");
    list.add("hh");
    list.add("lw");
    list.add("pqj");
    list.add("hj");
    System.out.println("前：");
    for(int i=0;i<list.size();i++){
      System.out.print(list.get(i)+"  ");
    }
    System.out.println("");
    System.out.println("后：");
    Collections.shuffle(list);
    for(int i=0;i<list.size();i++){
      System.out.print(list.get(i)+"  ");
    }