Error in arraylist

Question

    testSed4 = sedenia4.get(0);

    while (it8.hasNext()) {
        tempRozdiel = it8.next();
        tempSed4 = it7.next();

        if (testSed4.equals(tempSed4)) {
            testSed4 = tempSed4;
            casy.add(tempRozdiel);
        } else {
            casy.add(hodnota);
            testSed4 = tempSed4;
        }
    }
    for (int j = 0; j < casy.size(); j++) {
        System.out.println(casy.get(j) + " casy");
    }

Why I have error in line: tempRozdiel = it8.next();

What is bad in this code ?

What kind of error do you get? If it is a nullpointerexception you forgot to initialize your it8 arraylist object. — tim_a
– tim_a, Commented Dec 4, 2012 at 15:50
Exception in thread "main" java.util.ConcurrentModificationException at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:819) at java.util.ArrayList$Itr.next(ArrayList.java:791) at appidentifysession.AppIdentifySession.main(AppIdentifySession.java:36) Java Result: 1 — Majkl
– Majkl, Commented Dec 4, 2012 at 15:53
I can't get here full code because: "Oops! Your question couldn't be submitted because: Your post does not have much context to explain the code sections; please explain your scenario more clearly." What is bad on it ? — Majkl
– Majkl, Commented Dec 4, 2012 at 15:55
AppIdentifySession.java:36 is line which contains tempRozdiel = it8.next(); — Majkl
– Majkl, Commented Dec 4, 2012 at 15:56

Maxim Shoustin · Accepted Answer · 2012-12-04 16:02:07Z

2

Exception happens because you are modifying the collection over which it is iterating within the body of the iteration loop.

This is a reason why you got ConcurrentModificationException from iterator.next()

edited Dec 4, 2012 at 16:02

answered Dec 4, 2012 at 15:55

Maxim Shoustin

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3 Comments

Maxim Shoustin Over a year ago

@Majkl 1st off we don't know what is going on in your code since you provided as not enough info. Something changes your list during this action (you posted). About at8 iterator: post info about this list

Majkl Over a year ago

while (it1.hasNext()) { ipecka = it1.next(); agentik = it2.next(); spolu = ipecka + agentik; ipagent.add(spolu); } In this code is it OK, why not in next code?

Majkl Over a year ago

I have first list_session which contains 1,2,2,3 .Second list_time contains 30,17,25,46 .When second element of list_session is equals with first element, then add this time to third list_cas else add -1 .The same for third element and fourth etc.

UmNyobe · Accepted Answer · 2012-12-04 15:54:21Z

1

while (it8.hasNext()) {
    tempRozdiel = it8.next();
    tempSed4 = it7.next();

You are only checking if it8 has a next element, but not for it7.

Furthermore, you cannot use casy.add() if it7 or it8 are iterators on this object.

answered Dec 4, 2012 at 15:54

UmNyobe

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