java如何从ArrayList中排除空元素？

Question

//This code for mapping the elements inside xml tag  
public static String getLeukemiaInvolvement(String val) {
    BiMap<String, String> map = HashBiMap.create();
    map.put("01", "6");
    map.put("02", "7");
    map.put("03", "8");
    map.put("04", "9");
    map.put("05", "3");

    return map.inverse().get(val);
}

for (String data : getListStringValForElementTag(element, "organ-involvement1")) {
        if(data != null) {
            sectionAmlAllMds.getOrganInvolvement1().add(Pris3BMdmMapper.getLeukemiaInvolvement(data));
        }

    }

如何确保输出不包含null元素？我已经检查了null元素，但它不起作用。我的输出是：

 "organInvolvement1": ["01", "04", null, null, "05"]

此代码将读取XML标记“Organe-involvement1”内的元素数组列表：

getListStringValForElementTag(element, "organ-involvement1")

谢谢!