java 递归输入一个ID 怎么把这个ID下所有的子ID 放入一个list里面

HashMap> results = new HashMap>();
//输入的ID
                int ID=Integer.parseInt(Catid);
            //表中所有的数据
                aas=cloudnewscategory.selectAllGory();
                System.out.println("所有记录="+aas);
                for (CloudNewsCategory gory : aas) {
                    System.out.println("536456747="+results.get(gory.getPARENTID()));
                    List<CloudNewsCategory> beans = results.get(gory.getPARENTID());
                    if (beans == null) {
                        beans = new ArrayList<CloudNewsCategory>();
                        results.put(gory.getPARENTID(), beans);
                    }
                    beans.add(gory);               
                }
                displayMap(results,ID,"");  
public static void displayMap(HashMap<Integer, List<CloudNewsCategory>> results,
            int startKey, String str) {
        List<CloudNewsCategory> list = results.get(startKey);
// System.out.println("shuji="+results.get(startKey));
for (CloudNewsCategory gory : list) {
vv.add(gory.getID());
System.out.println(str + gory.getID() + "|"+gory.getCATEGORY());
if (results.containsKey(gory.getID())) {
displayMap(results, gory.getID(), str + " ");
            }

        }
    }

怎么得到一个list 里面是所有的子ID阿 急求