NullPointer Exception after checking with 'if' statement

Question

I have bot connected to IRC server and its not crashing all the time the bot is crashing with Exception in thread "main" java.lang.NullPointerException at bot.Report.main(Report.java:47) The 47 line is

if (!(str.split(" ")[1].equals("QUIT") || str.split(" ")[1].equals("PART") || str.split(" ")[1].equals("JOIN")))

Edit more code

String str = null;    
PrintWriter o;
            Socket s;
            BufferedReader i1;
            s = new Socket("", 6667);
            i1 = new BufferedReader(new InputStreamReader(s.getInputStream()));
            o = new PrintWriter(new OutputStreamWriter(s.getOutputStream()));
            o.print("PASS " + "" + "\r\n");
            o.print("USER " + "" + " 0 * :" + ""
                    + "\r\n" + "NICK " + "" + "\r\n");
            o.print("JOIN " + "#test" + "\r\n");
            o.flush();
    while (s.isConnected()) {
                str = i1.readLine();
                StringBuffer stringBuffer = null;
    if (!(str.split(" ")[1].equals("QUIT") || str.split(" ")[1].equals("PART") || str.split(" ")[1].equals("JOIN"))) {
    ......

Well if it's null, then why are you surprised about the null pointer exception? — Oliver Charlesworth, Apr 11 '15 at 09:22
`String str = null;` That will obviously give a nullPointerException , Since you are trying to split a string which is null. — Jonas Czech, Apr 11 '15 at 09:22
`null` has no `split` method (or any method nor field) so invoking it on `null` throws NPE. Also don't call `split` on same data multiple times if your data doesn't change. Call it once, store result and use it when you need it. — Pshemo, Apr 11 '15 at 09:23
Read the Javadoc for [`BufferedReader.readLine()`](https://docs.oracle.com/javase/8/docs/api/java/io/BufferedReader.html#readLine--) — Greg Kopff, Apr 11 '15 at 09:24
"*the str is not empty at all?*" no `null` is not the same as empty string `""`. — Pshemo, Apr 11 '15 at 09:26

score 1 · Accepted Answer · edited Apr 12 '15 at 00:46

1

It seems that if(str != null) fixed my problem.

edited Apr 12 '15 at 00:46

Radiodef

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answered Apr 11 '15 at 09:34

Даниел Димитров

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score 1 · Answer 2 · answered Apr 11 '15 at 09:38

As a good practice, you should always, check for null, before requesting for any of its, properties / methods.

if you could rewrite your if statement

if(str!=null && (!(str.split(" ")[1].equals("QUIT") || str.split(" ")[1].equals("PART") || str.split(" ")[1].equals("JOIN")))) ......

NullPointer Exception after checking with 'if' statement

2 Answers2