java.util.ConcurrentModificationException arises [duplicate]

Question

May Be it can be a duplicate question, I'm sorry for that. But my problem is not solving.

Below code gives me this exception (java.util.ConcurrentModificationException ) when execution reaches for 2nd time in foreach loop. Even i removed the arraylist object using iterator.

@RequestMapping("edit")
public ModelAndView editItemToInvoice(HttpSession session,@RequestParam("itemname")String itemname){

    ArrayList<InvoiceEntities> show=(ArrayList<InvoiceEntities>)session.getAttribute("invoices");

    if(show==null){
        show=new ArrayList<InvoiceEntities>();
    }

    ArrayList<InvoiceEntities> edit=new ArrayList<InvoiceEntities>();

    for(InvoiceEntities itemnam:show){
        if(itemnam.getItemName().equals(itemname)){
            int index=show.indexOf(itemnam);
            edit.add(show.get(index));

            Iterator<InvoiceEntities> iter = show.iterator();
            while(iter.hasNext()){
                InvoiceEntities getitem=iter.next();
                if(getitem.getItemName().equals(itemname)){
                    iter.remove();
                    //break;
                }
            }

        }
    }

    System.out.println(session.getAttribute("invoices"));

    ModelAndView model=new ModelAndView();
    session.setAttribute("invoices", show);
    model.addObject("editobj",edit);
    model.addObject("items",session.getAttribute("invoices"));
    model.setViewName("jsp/Invoice");

    return model;
}

Exception is java.util.ConcurrentModificationException

 SEVERE: Servlet.service() for servlet [spring-dispatcher] in context with  
 path [/Invoice] threw exception [Request processing failed; nested 
 exception is java.util.ConcurrentModificationException] with root cause
java.util.ConcurrentModificationException
at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:901)
at java.util.ArrayList$Itr.next(ArrayList.java:851)
at   mine.Controllers.InvoiceContorller.editItemToInvoice(InvoiceContorller.java:71)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:221)
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:137)
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:110)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:777)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:706)
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:943)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:877)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:966)
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:857)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:618)

I applied that solution you can see that i'm using iterator to remove the object. — Muhammad Danish Khan
– Muhammad Danish Khan, Commented Mar 24, 2015 at 7:29

Nir Alfasi · Accepted Answer · 2015-03-24 07:31:50Z

4

for(InvoiceEntities itemnam:show)

creates behind the scene an iterator of show, then inside the for loop you create another iterator:

Iterator<InvoiceEntities> iter = show.iterator();

and use the second iterator to modify show by calling iter.remove(); while the first iterator is still iterating the same collection.

See the paragraph that starts with "For example" in the documentation of ConcurrentModificationException for more information.

edited Mar 24, 2015 at 7:31

answered Mar 24, 2015 at 7:29

Nir Alfasi

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Comments

UmNyobe · Accepted Answer · 2015-03-24 07:26:48Z

3

When you perform

iter.remove();

you are modifying the collection while iterating on it with a different iterator. ArrayList doesnt allow that.

answered Mar 24, 2015 at 7:26

UmNyobe

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Comments

Viswanath Donthi · Accepted Answer · 2025-03-08 10:26:49Z

1

ArrayList is a Fail-Fast iterator collection. So, you should not modify while iterating it. You're trying to remove an item from the list in your code.

edited Mar 8 at 10:26

answered Mar 24, 2015 at 7:28

Viswanath Donthi

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