list集合转String类型，并拿出所有对象

例子：

  public static void main(String[] args) {

    ArrayList<String> arrayList = new ArrayList<String>();
    arrayList.add("啊哈哈");
    arrayList.add(" 反 ");
    arrayList.add(" 对 ");
    arrayList.add(" 胜利 ");
    arrayList.add(" 厉害 ");
    String[] str = new String[10];
    for (int i = 0; i <= 10; i++) {
      arrayList.add(String.valueOf(i));


    }

    String arr = arrayList.toString();
    String arrys = "";
    int count = 0;
    for (int i = 0; i <= arr.length(); i++) {
      if (i == 0) {
        String substring = arr.substring(arr.lastIndexOf(',') + 1, arr.length() - 1);
        arrys = substring;
        arr = arr.substring(1, arr.lastIndexOf(','));
      }
      if (i > 0 && i < 2) {
        for (int b = 0; b <= arrayList.size(); b++) {
          // 0, 2, 4, 6, 8
          String substring = arr.substring(arr.lastIndexOf(',') + 1, arr.length());
          if(!substring.contains(" ")){
              arrys = arrys + " " +substring;
          }else{
              arrys = arrys + substring;
          }
          arr=arr.trim();
          if (!arr.contains(",")) {
            break;
          }
            System.out.println(arr.length());
          arr = arr.substring(0, arr.lastIndexOf(','));
        }
      }
    }
    if(arrys.contains("0")){
      System.out.println("已有子集");
    }
      System.out.println(arrys);
    //
  }