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ConcurrentModificationException while using addAll method

Posted on 2009-05-13
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Last Modified: 2012-05-06
                 these loop will read the values from the form and put it in requestList.
                  
                  for (int i = 1; i <= 1; i++) {
                         cdtls= new ContainerDetails();
                         cdtls.setContainerType(request.getParameter("ContainerType_"+i+"_1"));
                         cdtls.setContainerNumber(request.getParameter("ContainerNumber_"+i+"_2"));
                         cdtls.setContainerDesc(request.getParameter("ContainerDescription_"+i+"_3"));
                         AL.add(cdtls);
                  }

                         ArrayList requestList=al;

                        //this list will give me first 10 records for the particular booking id;

                         ArrayList dataBaseList =DAO.getDBDetails(bookingId);

                  
                  ArrayList addList= new ArrayList();
                  addList.add("10");

                  // compared the addList number versus the dataBaseList ContainerDetails object id, if both r
                  same then first i need to remove that id from dataBaseList and then add requestList to dataBaseList.
                  i am getting java.util.ConcurrentModificationException while doing addAll method.
                  whats wrong with this code?

                  if(addList != null && !addList.get(0).equals("") && addList.size() > 0)
                        {
                              for (Iterator iterator = addList.iterator(); iterator.hasNext();) {
                                    String addId = (String) iterator.next();
                                    
                                    for (Iterator iterator2 = dataBaseList.iterator(); iterator2
                                                .hasNext();) {
                                          ContainerDetails object = (ContainerDetails) iterator2.next();
                                    
                                          if(object.getId() == Integer.parseInt(addId))
                                          {
                                                iterator2.remove();
                                                dataBaseList.addAll(al);
            
                                          }

                              }
                           }
                        }
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Question by:chaitu chaitu
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Expert Comment

by:Gibu George
ID: 24375143
Are you using Threads in the application
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Author Comment

by:chaitu chaitu
ID: 24375159
no
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Expert Comment

by:Gibu George
ID: 24375191
What type of application is this is it a web application?
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Author Comment

by:chaitu chaitu
ID: 24375220
yes
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Expert Comment

by:CEHJ
ID: 24375407
The first loop will only execute once, is that your intention?
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Accepted Solution

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CEHJ earned 500 total points
ID: 24375506
You can't addAll to dataBaseList while you're iterating it. Try instead:
        if(addList != null && !addList.get(0).equals("") && addList.size() > 0)
        {
            List temp = new ArrayList();
            for (Iterator iterator = addList.iterator(); iterator.hasNext();) {
                String addId = (String) iterator.next();
 
                for (Iterator iterator2 = dataBaseList.iterator(); iterator2
                        .hasNext();) {
                    ContainerDetails object = (ContainerDetails) iterator2.next();
 
                    if(object.getId() == Integer.parseInt(addId))
                    {   
                        iterator2.remove();
                        //dataBaseList.addAll(al);
                        temp.addAll(al);
 
                    }
 
                }   
            }   
            if (temp.size() > 0)
            {
                dataBaseList.addAll(temp);
            }
        }

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Expert Comment

by:objects
ID: 24380229
why not use a Map (keyed on id), that way you would not even need to loop at all.
using the appropriate data structure can greatly simplify your code

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Expert Comment

by:avya2k
ID: 24381903
As per specifications, you can not modify contents while iterating a collection
Instead collect all contents in temparory list and add it to main list after iteration
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Author Comment

by:chaitu chaitu
ID: 24382038
objects,

can you give me some hint what you are trying to tell?
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Expert Comment

by:objects
ID: 24382046
for example if you had a map keyed on id you would not need to loop through every element looking for a particular id.

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Expert Comment

by:CEHJ
ID: 24383323
>>Instead collect all contents in temparory list and add it to main list after iteration

(which is what happens in the code i posted)

chaituu, what result do you get when you run that?
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Author Comment

by:chaitu chaitu
ID: 24392159
CEHJ,

ur solution is working.i thought i am doing some unwanted code thats why i am taking objects suggestion.
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Expert Comment

by:CEHJ
ID: 24412017
:-)
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