2 dimensional string array declaration, Exception in thread "main" java.lang.NullPointerException java

Question

I'm new to java programming and I can't find a solution to my problem. I think it's a pretty easy problem but I can't figure a what I'm doing wrong so I hope one of you could help me. The problem is when I try to store some data in an array it returns the following error:

Exception in thread "main" java.lang.NullPointerException

Code

public class FetchData{
    private String rows[][];
    private int rowCount;

    public FetchData(){
        rowCount = 0;
    }

    public boolean ConnectAndFetch(String start, String end){

        //not relevant to the problem
        for(...){
            List<WebElementdivList = driver.findElements(By.tagName("div"));

            int divCount = 0;
            int colCount = 0;
            for (WebElement elem : divList) {
                if(divCount 24){ 
                    if(colCount < 17){
                        System.out.println(elem.getText());
                        //System.out.println(colCount);
                        //System.out.println(rowCount);
                        rows[rowCount][colCount] = elem.getText();
                        colCount++;
                    } else { 
                        rowCount += 1;
                        colCount = 0;
                    }
                }
                divCount++;
            }
        }
        return true;
    }

I think it has something to do with the declaration private String rows[][]; but I don't know how to fix it. I'd appreciate your help!

Bernard · Accepted Answer · 2012-05-12 16:48:39Z

9

You need to initialize your rows array first before you can store values in it:

String[][] rows = new String[10][10];

Use any size you need. I chose 10 randomly. I suggest initializing the array in your class constructor.

answered May 12, 2012 at 16:48

Bernard

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4 Comments

Andrew Thompson Over a year ago

"Use any size you need." Within OutOfMemoryError or MAX_VALUE. ;)

Bernard Over a year ago

@Andrew Thompson: Agreed. Reasonable sizes only.

Thihara Over a year ago

Also you may want to take a look at Java Collection API docs.oracle.com/javase/7/docs/api/java/util/Collections.html. It's much more powerful than arrays.

Jab Over a year ago

Thanks, this will work for now, ill take a look to te Collection later when i got some more time. Thanks for your awnsers!

Vipul · Accepted Answer · 2012-05-12 17:02:08Z

4

You declared string array but not initialized it... before using it you must initialized it as
row=new String [1][1]. Since you declared array as a instance variable the default value assign to it is null that's why u are getting null pointer exception. For more about array visit following link:
http://docs.oracle.com/javase/tutorial/java/nutsandbolts/arrays.html

edited May 12, 2012 at 17:02

answered May 12, 2012 at 16:54

Vipul

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