java - nullpointer exception

Question

Guys i need some help here , im getting this error here at the code snippet below. here's the stack trace. i have a feeling that somebody's gonna say not much effort on my part. its ok i agree , give me a suggestion what should i do more and ill do it just that i've got a little stuck and not moving ahead so thought of posting it here.

i think i'm having a problem because i'm using a code that was used for writing an excel file when the size of content to write to excel was pre - known . what i actually need is some way to write to excel when the length of rows and collumns may vary .

Length of Array:2000
java.lang.NullPointerException
    at org.temp2.cod2.WriteToExcel.setExcel(WriteToExcel.java:149) >> line 149 is last line of the code snippet below i.e. byte buf[] = s.getBytes();

here the code snippet

String data[][] = new String [2000][5];

System.out.println("Length of Array:"+data.length);

for(int j=0;j<colN.length;j++){
    Label myLabel1=new Label(j,1,colVal[j]);
    wst.addCell(myLabel1);
}

for(int i=2;i<=data.length+1;i++){
    for(int j=0;j<colN.length;j++)
    {
            // Encrypt
            encrypter.encrypt(new FileInputStream("C:\\Users\\abc\\Desktop\\Encrypted.txt"),new FileOutputStream("temp.txt"));
            // Decrypt

            ByteArrayOutputStream f = new ByteArrayOutputStream();
            String s = data[i-2][j];
            byte buf[] = s.getBytes();

Code looks better with spaces instead of tabs.

R. Martinho Fernandes
– R. Martinho Fernandes

2009-11-24 15:56:09 +00:00
Commented Nov 24, 2009 at 15:56 — R. Martinho Fernandes
– R. Martinho Fernandes, Commented Nov 24, 2009 at 15:56

Bob · Accepted Answer · 2009-11-24 15:54:09Z

4

Your reference to s in s.getBytes is probably null. So that means what is getting executed is something like

byte buf[] = null.getBytes();

Which doesn't make much sense. So what you want to do to correct this might be something like this

String s = data[i-2][j];
byte buf[];
if (s != null) 
    buf = s.getBytes();
else
   buf = //What do you want the default behavior to be? maybe "".getBytes()?

answered Nov 24, 2009 at 15:54

Bob

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1 Comment

Pascal Thivent Over a year ago

Don't expect s to be not null with the actual code. BTW, avoiding using brackets is really not a good idea, even for a single line.

Bozho · Accepted Answer · 2009-11-24 15:53:21Z

2

Obviously data[i-2][j] is null. You are not setting it anywhere, so it is null.

answered Nov 24, 2009 at 15:53

Bozho

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Comments

Mr. Shiny and New 安宇 · Accepted Answer · 2009-11-24 15:58:33Z

1

At what point do you initialize the data[][] array?

String data[][] = new String [2000][5];

allocates the space but it appears that you never put any Strings in the array.

Also I feel I should point out that string.getBytes() is not character-encoding safe. You should always specify the character encoding, such as UTF-8 or UTF-16. Remember, the characters in the string are not equivalent to bytes; getBytes() transforms the data.

answered Nov 24, 2009 at 15:58

Mr. Shiny and New 安宇

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Comments

Pascal Thivent · Accepted Answer · 2009-11-24 16:26:31Z

1

Looks like data[i-2][j] is null. Is it supposed to be non null? Check how you are initializing it then because, currently, you're just declaring data[][] to be a String[2000][5] array, you're not initializing its content. So it's filled with nulls.

edited Nov 24, 2009 at 16:26

answered Nov 24, 2009 at 15:52

Pascal Thivent

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Comments

DKSRathore · Accepted Answer · 2009-11-24 16:50:35Z

0

Hey rover, You have declared your array of array as

String data[][] = new String [2000][5];

and you are accessing the location [2000]. In the above array your index should always be less that 2000.

answered Nov 24, 2009 at 16:50

DKSRathore

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Comments

Jared Russell · Accepted Answer · 2009-12-07 17:10:02Z

0

You never initialize the contents of the array. You will need to loop over the array and assign strings to the elements:

String[][] data = new String[2000][5];

for(int i = 0; i < data.length; i++) {
    for(int j = 0; j < data[i].length; j++) {
        data[i][j] = new String(...);
    }
}

edited Dec 7, 2009 at 17:10

answered Nov 24, 2009 at 15:59

Jared Russell

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