CODEWITHSUNDEEP
javajakarta-mail
user3872094
user3872094

Reputation: 3351

null subjectline giving null pointer exception

With the below code i'm trying to get only the emails that matches the subject line.

String subject = "test email";
    Properties props = System.getProperties();
    props.setProperty("mail.store.protocol", "imaps");
    try {
        Session session = Session.getDefaultInstance(props, null);
        Store store = session.getStore("imaps");
        store.connect(host, userName, password);
        Folder inbox = store.getFolder("Inbox");
        inbox.open(Folder.READ_ONLY);
        int count = inbox.getMessageCount();
        System.out.println(count + " total messages");
        Message messages[] = inbox.getMessages();
        for (int i = 0; i < messages.length; i++) {
            if (messages[i].getSubject().contains(subject)) {
                System.out.println(messages[i].getSubject() + "\t"
                        + messages[i].getSentDate());
            } else {
                System.out.println("subject mismatch");
            }
        }

here i'm getting the required result, but the problem kicks when there is a email with no subject line.

I tried the below.

else if (messages[i].getSubject().contains(null)) {
                    System.out.println(messages[i].getSubject() + "\t"
                            + messages[i].getSentDate());
                }


else if (messages[i].getSubject().contains("")) {
                    System.out.println(messages[i].getSubject() + "\t"
                            + messages[i].getSentDate());
                }


else if (messages[i].getSubject().contains(" ")) {
                    System.out.println(messages[i].getSubject() + "\t"
                            + messages[i].getSentDate());
                }

but still i get the below error

java.lang.NullPointerException
    at com.getEmails.readEmails.main(readEmails.java:34)

also instead of contains, i tried equals and equalsIgnoreCase, but still the issue is same.

when printing just subject line without the condition, it was showing null as subject line. So i tried the below.

else if (messages[i].getSubject().contains("null")) {
                        System.out.println(messages[i].getSubject() + "\t"
                                + messages[i].getSentDate());
                    }

but still the error is same.

please let me know how can i fix this.

Upvotes: 0

Views: 238

Answers (4)

Bill Shannon
Bill Shannon

Reputation: 29971

In addition to what everyone else said, you might want to look into using the Folder.search method with a SubjectTerm, which will allow the searching to be done on the server:

Message[] messages = inbox.search(new SubjectTerm(subject));
for (int i = 0; i < messages.length; i++) {
    System.out.println(messages[i].getSubject() + "\t"
                    + messages[i].getSentDate());
}

Upvotes: 0

prsmax
prsmax

Reputation: 223

messages[i] != null && messages[i].getSubject() != null && messages[i].getSubject().contains(subject)

Upvotes: 1

npinti
npinti

Reputation: 52195

The problem is that whatever the getSubject() yields can sometimes be null, thus any operations on that will yield a NullPointerException, regardless of what type of check you do.

To go around this problem you will need to make a null check, something like so:

        for (int i = 0; i < messages.length; i++) {
            if ((messages[i].getSubject() != null) && (messages[i].getSubject().contains(subject))) {
                System.out.println(messages[i].getSubject() + "\t"
                        + messages[i].getSentDate());
            } else {
                System.out.println("subject mismatch");
            }
        }

Upvotes: 2

Akash Thakare
Akash Thakare

Reputation: 23012

You should check for null first as it will give NullPointerException if messages[i] OR messages[i].getSubject() is null. Apart from that contains(null) has no meaning and must cause NullPointerException but messages[i].getSubject() == null does make sense.

Upvotes: 1

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