如何将dropdownlist选定值存储到arraylist会话中？

<select id="dropdownlist">
  <option value="value1">Option 1</option>
  <option value="value2">Option 2</option>
  <option value="value3">Option 3</option>
</select>

<button onclick="storeSelectedValue()">Store Value</button>

function storeSelectedValue() {
  // 获取dropdownlist元素
  var dropdownlist = document.getElementById("dropdownlist");
  
  // 获取选定的值
  var selectedValue = dropdownlist.value;
  
  // 创建或获取arraylist会话对象
  var arrayList = sessionStorage.getItem("arrayList");
  if (arrayList) {
    arrayList = JSON.parse(arrayList);
  } else {
    arrayList = [];
  }
  
  // 将选定的值存储到arraylist会话中
  arrayList.push(selectedValue);
  
  // 更新arraylist会话对象
  sessionStorage.setItem("arrayList", JSON.stringify(arrayList));
}

// 读取arraylist会话对象
ArrayList<String> arrayList = (ArrayList<String>) session.getAttribute("arrayList");

// 遍历arraylist获取存储的选定值
for (String value : arrayList) {
  System.out.println(value);
}