Am getting java.util.ConcurrentModificationException while accessing Hashma

Question

Hi,
I written code as below
public String createHM2Req(String ReqFileNm) throws Exception
          String retVal="";
          String strId = "";
          try
System.out.println(" --- LSReqFileNm "+ReqFileNm);
System.out.println(" -- hmReqData "+hmReqData);
strId = "TE"+getValHMProcessReq("SubjBorrId");
if(!getValHMProcessReq("SpouseId").equals("") && getValHMProcessReq("ServiceTypCd").equals("ABCD"))
strId += " TE"+getValHMProcessReq("SpouseId");
public String getValHMProcessReq(String key) throws Exception
String retVal="";
          try
               if(key != null && !key.equals(""))
                    if(!checkNull(hmReqData.get(key)+"").equals(""))
                         retVal = hmReqData.get(key).toString();
                         retVal = escape(retVal);
          catch(Exception e)
               e.printStackTrace();
          return retVal;
Am getting below exception at run time
Caused by: java.util.ConcurrentModificationException
     at java.util.HashMap$HashIterator.nextEntry(HashMap.java:782)
     at java.util.HashMap$EntryIterator.next(HashMap.java:824)
     at java.util.AbstractMap.toString(AbstractMap.java:586)
     at java.lang.String.valueOf(String.java:2131)
     at java.lang.StringBuffer.append(StringBuffer.java:370)

Answer 1

Something is calling toString on a map and something else is modifying that map. toString will start iterating. You probably get that exception if another request at the same times modifies the map.