CODEWITHSUNDEEP
java
rover12
rover12

Reputation: 2906

java - nullpointer exception

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();

Upvotes: 1

Views: 3894

Answers (6)

Jared Russell
Jared Russell

Reputation: 11332

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(...);
    }
}

Upvotes: 0

DKSRathore
DKSRathore

Reputation: 3063

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.

Upvotes: 0

Pascal Thivent
Pascal Thivent

Reputation: 570315

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.

Upvotes: 1

Mr. Shiny and New 安宇
Mr. Shiny and New 安宇

Reputation: 13908

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.

Upvotes: 1

Bob
Bob

Reputation: 99694

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()?

Upvotes: 4

Bozho
Bozho

Reputation: 597046

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

Upvotes: 2

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