判斷List是否包含某個元素

				List deviceCollectCodeList = new ArrayList();
				String deviceCollectCode = "a";
				boolean checkDeviceCollectCode = deviceCollectCodeList.contains(deviceCollectCode);
				if (checkDeviceCollectCode == true) {
					System.out.println("已存在");
					break;
				} else {
					deviceCollectCodeList.add(deviceCollectCode);
				}