我正在使用Collection只能迭代数组或java.lang.Iterable的实例

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)

Answer 1

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.