i am using Collection Can only iterate over an array or an instance of java.lang.Iterable

Question

I am trying to solve this error, but for some reason, not able to find the issue to fix it. I am using Collection in this code. If anyone can point me out what actually I am missing, I would be a great help.

Collection challenges = null;
        Map challengesMap = new HashMap<String,String>();
        ForgotPasswordManager forgotPwdMgr = new ForgotPasswordManager(platform);
        System.out.println("after ForgotPasswordManager(platform)...before getSecretQuestion()");
        challenges = forgotPwdMgr.getSecretQuestion(userID);
        System.out.println("after getSecretQuestion()...");
        for (Object challenge : challenges) {
            String challengeStr = (String)challenge;
            System.out.println("doGetChallenges()...ChallengeStr = " + challengeStr);
            challengesMap.put(challengeStr.trim(), "");
        }

I am getting this error Can only iterate over an array or an instance of java.lang.Iterable on line: for (Object challenge : challenges)

Possible duplicate of Error: can only iterate over an array or an instance of java.lang.Iterable. The second answer explains the problem. — Tot Zam
– Tot Zam, Commented Aug 2, 2017 at 21:17

davidxxx · Accepted Answer · 2017-08-02 21:21:59Z

3

The Collection type referenced here :

Collection challenges = null;

is not the java.util.Collection interface that extends the Iterable interface.
Otherwise you would have not this error message :

Can only iterate over an array or an instance of java.lang.Iterable

at this line :

for (Object challenge : challenges) {

You are using probably a custom Collection class.

So to solve your problem, make your custom custom Collection class implement Iterable or more simple : use JDK java.util.Collection subclasses.

edited Aug 2, 2017 at 21:21

answered Aug 2, 2017 at 21:18

davidxxx

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6 Comments

newlearner Over a year ago

can you elaborate little bit more i am little confuse @davidxxx

davidxxx Over a year ago

Ok. Look at the package of the Collection class in your imports. You will see that is not java.util.Collection. So it means that you use your own Collection class.

newlearner Over a year ago

i am using the import.java.util.Collection when i click on Declared type it brings me to the Collection class @davidxxx

davidxxx Over a year ago

I suppose you have a Collection class in the package of the actual class that declares this code ?

newlearner Over a year ago

i didn't define the Collection class in my code after importing it could that be the reason because i am only using collection on this piece of the code @davidxxx

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