Question

removing elements from a arraylist

Asked by: jaggernat

hi guys
I have an arraylist
List itemList = theForm.getList(); // itemList  has objects of type CustomerVO in it.
If itemList has more than one object, i want to keep the first object and delete the rest of the objects.
Any idea how i can do this.

Thx v much
 

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Asked On
2009-09-26 at 10:29:07ID24764167
Topic

Java Programming Language

Participating Experts
2
Points
500
Comments
14

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Answers

 

by: CEHJPosted on 2009-09-26 at 10:37:50ID: 25430528

Try


List itemList = theForm.getList();
int size = itemList.size();
if (size > 1) {
    itemList. removeRange(1, size);
} 

                                              
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by: jaggernatPosted on 2009-09-26 at 10:46:28ID: 25430555

hi ,
thx for the reply. It says removeRange is undefined for type list

 

by: CEHJPosted on 2009-09-26 at 10:56:54ID: 25430582

All are likely to be AbstractList, so try the below. If you are worried about that, loop backwards and remove while index >= 1

((AbstractList)itemList).removeRange(1, size);
                                              
1:

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by: CEHJPosted on 2009-09-26 at 11:07:15ID: 25430670

A solid way is the following

List itemList = theForm.getList();
int size = itemList.size();
if (size > 1) {
	Iterator i = itemList.iterator();
		i.next();
		while(i.hasNext()) {
			i.remove();
		}
} 

                                              
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by: CEHJPosted on 2009-09-26 at 11:08:13ID: 25430682

oops: lines 5-8 one tab too many

 

by: jaggernatPosted on 2009-09-26 at 11:08:47ID: 25430689

unfortunately >> ((AbstractList)itemList).removeRange(1, size);  doesnt seem to work, same error

so are you saying
for(int i=0 i >itemList.size ;i--){
while(index >= 1){
remove(i)
}
}

 

by: jaggernatPosted on 2009-09-26 at 11:34:41ID: 25430929

ok tried your solution, somehow when there are 2 objects in the list, it remves the second one but then throws an error on  remove(i).

dardWrapperValve[action]: Servlet.service() for servlet action threw exception
java.lang.IllegalStateException
      at java.util.AbstractList$Itr.remove(AbstractList.java:433)
      at com.vzw.cpi.web.customer.MaintainCustomerAction.replicateMode
      at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
      at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
      at java.lang.reflect.Method.invoke(Method.java:585)
      at org.apache.struts.actions.DispatchAction.dispatchMethod(DispatchAction.java:2

 

by: jaggernatPosted on 2009-09-26 at 11:41:49ID: 25430980

thnk this should fix it

ist itemList = theForm.getList();
int size = itemList.size();
if (size > 1) {
      Iterator i = itemList.iterator();
            i.next();
            while(i.hasNext()) {
                  i.remove();
if( itemList.size() == 1){
                                                 break;
                                           }
            }
}

 

by: jaggernatPosted on 2009-09-26 at 11:46:10ID: 25431006

another problem is for some reason if there are 2 objects in the list, its deleting the first object and keeping the second one. I want it other way round, i want it to keep the first object and delete the rest

 

by: jaggernatPosted on 2009-09-26 at 11:52:41ID: 25431035

oops, just checked with three objects in the list. Some how that fails too on the >>i.remove();.
 i think i  is not getting incremented

 

by: rrz@871311Posted on 2009-09-26 at 16:19:21ID: 25432005

CEHJ  forgot one line.  Try the following.

List itemList = theForm.getList();
int size = itemList.size();
if (size > 1) {
        Iterator i = itemList.iterator();
                i.next();
                while(i.hasNext()) {
                        i.next();
                        i.remove();
                }
} 

                                              
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Select allOpen in new window

 

by: CEHJPosted on 2009-09-27 at 01:34:23ID: 25433157

>>CEHJ  forgot one line.

Oops yes. Thanks rrz

>>
so are you saying
for(int i=0 i >itemList.size ;i--){
while(index >= 1){
remove(i)
}
}
>>

No, that should be:

for(int i=itemList.size() - 1;i >0;i--) {
	itemList.remove(i);
}
                                              
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3:

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by: jaggernatPosted on 2009-09-28 at 07:31:48ID: 25439657

thank you

 

by: CEHJPosted on 2009-09-28 at 10:21:57ID: 25441253

:-)

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