Member Avatar for kukuruku

I am trying to fill up the array den and it is giving me java.lang.NullPointerException
Why is that
Thanks

public static void main(String[] args) {
        Scanner input=new Scanner(System.in);
        System.out.print("Enter an amount:");
        float amount= input.nextFloat();
        int denom, i=0;
        int  [] den=null;
        do{
        System.out.print("Enter denominations: ");
        denom=input.nextInt();
        den[i]=denom;
        i++;
        }
        while(denom!=0);
Edited by kukuruku because: n/a
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  • Latest Post Latest Post by stultuske
Member Avatar for stultuske 
int  [] den=null;
[/Code=Java]

this is why ... before you want to set values like this:
[Code=Java]
den[i]=denom;

you have to set a length for the array, for instance:

int[] den = new int[5]; // creates an int - array with 5 elements

this 'll also tell you ... you can't use an array in the logic you're trying to implement. if you want to add elements until you enter '0', you need to use a List.

List numbers = new ArrayList();
int nr = readNumber(); // let's just assume this method exists
while ( nr != 0 ){
numbers.add(nr); // autowrapping takes care of the transfer to Integer
nr = readNumber();
}
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