Null pointer Exception in Java when assigning value to int array

Question

My code shows null pointer exception when i assign values to int array in the object:

public class Cage {
    int Value;  
    String Operator;
    int[] placeHolders;
}

Cage o = new Cage();                
o.Value = Integer.parseInt(strSplit[0]);
o.Operator = strSplit[1];               
for(int i=2;i<strSplit.length;i++) {
    o.placeHolders[i] = Integer.parseInt(strSplit[i]);
}

You should read the Arrays section of the Java Tutorial, especially the parts about Declaring a Variable to Refer to an Array and then Creating, Initializing, and Accessing an Array — mikej
– mikej, Commented Sep 21, 2012 at 8:45

KARASZI István · Accepted Answer · 2012-09-21 08:44:47Z

4

You should create an int array for your placeHolders, it's just a declaration, not a definition right now.

o.placeHolders = new int[strSplit.length];

answered Sep 21, 2012 at 8:44

KARASZI István

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3 Comments

mikej Over a year ago

You could make the size of the array strSplit.length - 2 as the first 2 elements from strSplit don't go in placeHolders.

KARASZI István Over a year ago

But in that case the array index should changed, in the example it's not zero based.

mikej Over a year ago

Yep, so I suppose it just depends on whether the OP wants a gap at the start of the array.

maba · Accepted Answer · 2012-09-21 08:57:48Z

2

I guess that you want to have placeHolders to hold values without null values in the first to indexes.

o.placeHolders = new int[strSplit.length - 2];
for (int i = 0; i < strSplit.length - 2; i++) {
    o.placeHolders[i] = Integer.parseInt(strSplit[i + 2]);
}

answered Sep 21, 2012 at 8:57

maba

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Comments

Random42 · Accepted Answer · 2012-09-21 08:44:05Z

0

You should instantiate the int[] object before using it:

int[] placeHolders = new int[100];

answered Sep 21, 2012 at 8:44

Random42

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4 Comments

CodeMonkey Over a year ago

int[100] is hard coding.. i guess not a very good style . thx for helping though

Random42 Over a year ago

@V.J. The you should use a list: List<Integer> placeHolders = new ArrayList<Integer>();

mikej Over a year ago

But in this case an array is fine because you know the size required from the length of strSplit.

Random42 Over a year ago

@mikej then you instantiate the array object with that particular length; anyway, the problem was that the object was not instantiated.

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