How to check if processing the last item in an Iterator?

Question

If I have an iterator and I want to check the last value, how can I check it? Like

private Set<String> saarcCountries = new TreeSet<String>();
Iterator iter = saarcCountries.iterator();

while(iter.hasNext()) {

    String name = (String)iter.next();
    int countryId = Integer.parseInt(name);

    newsOrAnnouncementInsert.add(newsId);
    newsOrAnnouncementInsert.add(countryId);
    newsOrAnnouncementInsert.add(1);            //addby

    if (!(last value in iterator))) {
        newsOrAnnouncementInsert.add("~!~");//Delimiter for Multiple Detail Records
    }//end if

} //end of while

How can I check for last value. what should replace last value in iterator?

Check out this one as well http://stackoverflow.com/questions/285523/last-iteration-of-for-loop-in-java — Sanghyun Lee, Apr 18 '15 at 07:16

score 35 · Answer 1 · answered Mar 09 '12 at 12:23

35

If iter.hasNext() is false after iter.next() then it is the last item.

Happy coding.

answered Mar 09 '12 at 12:23

score 34 · Accepted Answer · answered Mar 09 '12 at 12:24

34

You can check it just like you do in the while condition:

if ( ! iter.hasNext()) {
    // last iteration
    ...
}

answered Mar 09 '12 at 12:24

DerMike

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lilalinux · Answer 3 · 2015-06-09T09:41:02.920

13

This answer is not specific to an Iterator, but can be used for any iterating statement where you need to insert a separator between items. It doesn't need to know the current index nor does it need any condition.

String previousSeparator = "";
for (String value : collection) {
  System.err.println(previousSeparator + value);
  previousSeparator = ",";
}

edited Jun 09 '15 at 09:41

answered Jun 09 '15 at 08:41

lilalinux

2,903
3
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1

Nice and simple. I wonder why that common problem doesn't have a standard solution? It probably has in one of the many libraries, I just don't know it. – jackthehipster Feb 06 '18 at 14:14

score 3 · Answer 4 · answered Oct 29 '14 at 02:53

This question is old, the answer is good, but I used this answer to figure out how to add commas between list items and add an end of list delimiter. In case someone else like me is looking for the same thing here's what I did:

public String toString() {

    StringBuilder sb = new StringBuilder();

    sb.append("List contains:\n");

    Iterator<String> iterator = list.iterator(); 

    while(iterator.hasNext()){

        // Get the next element.
        sb.append(iterator.next());

        // If there is another element add a comma.
        if(iterator.hasNext()){
            sb.append(", ");
        }else{
            sb.append(" ~!~");
        }
    }

    return sb.toString();
}

score 3 · Answer 5 · answered Mar 09 '12 at 12:24

3

Although other answers gave some ideas, I think it is better to add it without the condition and remove the last delimiter after the while loop terminates.

answered Mar 09 '12 at 12:24

MByD

135,866
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3

"Ewwwww!" This just makes me think of horrid string joining support in java :( – Mar 09 '12 at 12:25
@pst - Maybe, but I try to avoid branches when I can. – MByD Mar 09 '12 at 12:26

score 3 · Answer 6 · answered Mar 09 '12 at 12:31

Use StrBuilder (an apache commons lang class) as the type of newsOrAnnouncementInsert. Then use the StrBuilder.appendSeperator() method.

For example

StrBuilder newsOrAnnouncementInsert = new StrBuilder();

while (iterator.hasNext())
{
    newsOrAnnouncementInsert.appendSeperator("~!~");

    String name = (String)iter.next();
    int countryId = Integer.parseInt(name);

    newsOrAnnouncementInsert.add(newsId);
    newsOrAnnouncementInsert.add(countryId);
    newsOrAnnouncementInsert.add(1);
}

appendSeperator only adds the seperator if the buffer is not currently empty (in this case, if this is the first time through the loop).

Basically, you want to invert the comparison. Don't check to see if you are on the last element of the itnerator, instead check to see that you are not processing the first element. If not the first element, append the seperator then append the current element.

Thanks but i need a library for using **StrBuilder**. Anyways thanks :) — Basit, Mar 09 '12 at 12:59

score 0 · Answer 7 · answered Mar 09 '12 at 12:24

0

How about this:

if (!(iter.hasNext())) {
    newsOrAnnouncementInsert.add("~!~");//Delimiter for Multiple Detail Records
}

answered Mar 09 '12 at 12:24

nwinkler

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score 0 · Answer 8 · answered Mar 09 '12 at 12:25

0

You can use the hasNext method to check if this is the last value. If you don't have any next values, this means it is the last value.

answered Mar 09 '12 at 12:25

Tiago Pasqualini

821
5
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score 0 · Answer 9 · answered Mar 09 '12 at 12:52

If you don't have access to the Iterator you can use this approach.

boolean afterFirst = false;
for(String name : saarcCountries) {
    if(afterFirst)
       newsOrAnnouncementInsert.add("~!~");
    afterFirst = true;

    newsOrAnnouncementInsert.add(newsId);
    newsOrAnnouncementInsert.add(name);
    newsOrAnnouncementInsert.add(1);
}

Say its a StringBuilder

StringBuilder newsOrAnnouncementInsert = new StringBuidler();
String sep = "";

for(String name : saarcCountries) {
    newsOrAnnouncementInsert.append(sep + newsId + name + 1);
    sep = "~!~";
}

How to check if processing the last item in an Iterator?

9 Answers9