Java.NullPointerException null (again)

Question

I am having another problem with NullPointerException. This time it is highlighting tellen = telno.length(). Beore you ask:

There is data in the text file to be read to that variable.
All variables were initialized.
Buffered Reader is also initialized.

Here is a snippet of my code:

while((telno = br.readLine()) != null){
    name = br.readLine();

    surname = br.readLine();

    company = br.readLine();

    house = br.readLine();

    street = br.readLine();

    locality = br.readLine();

    postcode = br.readLine();

    telno = br.readLine();
    tellen = telno.length();

    mobno = br.readLine();

    sep = br.readLine();

    if(tellenx > tellen) tellen = tellenx;


}

Please help. Thanks. Text file:

Name
Surname
Company
House
Street
Locality
Telephone number
Mobile Number

Problem is in the telephone (tellen) All these names are fictional, and this program is a telephone directory

George
Farrugia
Some Company 
9, Flowers
Quail Street
Bubaqra
BBQ 1569
21369854
79825643
--------------------------------------------
Paul
Zammit

9
Bird Street
St. Julians
STJ 0000
21545796
79745247
--------------------------------------------
Peter
Spiteri
Oak Company
Trees
Birch Street
Oakgrove
TRE 3333
21323323
99323323
--------------------------------------------

The blank after Zammit is a space. That is placed if there is no data to avoid a problem like this.

Please post the stack trace for the null pointer exception. It probably has a clue to offer.. — Stefan Rasmusson
– Stefan Rasmusson, Commented Jan 31, 2013 at 18:09
Can you post a sample of the input file. You say that there is data for all fields it would be nice to see a sample. — Manuel Quinones
– Manuel Quinones, Commented Jan 31, 2013 at 18:11
You realize that you do tellno = br.readLine() twice, and ignore the first value right? — Mark Peters
– Mark Peters, Commented Jan 31, 2013 at 18:12

Smit · Accepted Answer · 2013-02-01 01:17:04Z

1

This error is getting caused because you are reading 11 lines in one while loop instead you have to read 10 lines only.

So at some point br.readLine() will return null.

You need to read file according to your need that means in one go (your while loop) read 10 lines, then next 10 lines and so on.

while((telno = br.readLine()) != null){ // first line
    name = br.readLine();   // secondline I think this should be first line

    surname = br.readLine();

    company = br.readLine();

    house = br.readLine();

    street = br.readLine();

    locality = br.readLine();

    postcode = br.readLine();

    telno = br.readLine();
    tellen = telno.length();

    mobno = br.readLine();

    sep = br.readLine();  // eleventh line

    if(tellenx > tellen) tellen = tellenx;


}

edited Feb 1, 2013 at 1:17

answered Jan 31, 2013 at 18:58

Smit

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3 Comments

Mark Said Camilleri Over a year ago

Thanks for explaining this to me. With your answer I managed to solve this problem. Thanks again. When I'll have 15 rep points, I'll vote you up:)

Smit Over a year ago

You are welcome. Just a advice. Next time when you caught in this problem try to debug and find the problem yourself. It will help you in long run. If you are using Eclipse then Eclipse Debugging Tutorials

Mark Said Camilleri Over a year ago

Actually, I am using BlueJ. To be frank, I am still studying for my 'O' Levels / GCSE Equivalent which is why I am not experienced in these matters.

PermGenError · Accepted Answer · 2013-01-31 18:09:03Z

1

Most probably its the end of the file and your bufferedReader.readLine() is returning null and you just invoked a method on an instance which is null, which leads to NPE.

answered Jan 31, 2013 at 18:09

PermGenError

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2 Comments

Mark Said Camilleri Over a year ago

There is data in the text file. None of the lines are null. It was working fine before I added another set of data. Same fields as this is what the program was designed to do.

PermGenError Over a year ago

@markscamilleri at the end of the file, if there is nothing to read br.readLine() returns null.

Renjith · Accepted Answer · 2013-01-31 18:11:03Z

0

I guess you are trying to read using readLine() without null check.Definitel, it will give NPE.

answered Jan 31, 2013 at 18:11

Renjith

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Comments

Smit · Accepted Answer · 2013-01-31 18:48:29Z

0

Adding an if statement to check if there is any null references is a good practice to check for an error in your code.

An example in pseudo code would be:

   telno = br.readLine();

   if(telno == null)
       System.out.println("this will cause null pointer exception  "+ telno.length()); 
   else
       tellen = telno.length();

edited Jan 31, 2013 at 18:48

Smit

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answered Jan 31, 2013 at 18:22

Brian Var

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2 Comments

Mark Said Camilleri Over a year ago

Tried it, and it is giving me a NullPointerException when there IS data. I don't know what's happening.

Smit Over a year ago

I think you mean to say == and you also need to remove lines after if and else.

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