for-each loop NullPointerException

Question

i keep getting nullpointerexception no matter what i tried. can provide more code if required.

public int howManyBetweenTheseYears(int startYear, int endYear){
    ArrayList<Lamborghini> selectedCars = new ArrayList<Lamborghini>();

    for(Lamborghini c : inventory){
        if(c == null){
            continue;
        }
        if(c.getModelYear()>= startYear && c.getModelYear()<= endYear){
            selectedCars.add(c);
        }
    }
    return selectedCars.size();
}

why do you overload your logic with adding the cars into the array list if you just return the size of this list? why not using a counter? — Arthur Eirich, Jun 17 '15 at 05:30
Could you please put the stack trace, so tht we can see where the NPE is coming from? — Anand S Kumar, Jun 17 '15 at 05:31
possible duplicate of [What is a Null Pointer Exception, and how do I fix it?](http://stackoverflow.com/questions/218384/what-is-a-null-pointer-exception-and-how-do-i-fix-it) — Tom, Jun 17 '15 at 06:26

Jens · Answer 1 · 2015-06-17T06:28:58.687

0

It looks like inventory is null.

edited Jun 17 '15 at 06:28

answered Jun 17 '15 at 05:29

Jens

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If `inventory` is empty list, i dont think there will be an NPE. It should be null. – Codebender Jun 17 '15 at 05:30

score 0 · Answer 2 · answered Jun 17 '15 at 05:47

0

if getModelYear returns null then you will get NullPointerException

answered Jun 17 '15 at 05:47

mokarakaya

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Ashish Patil · Answer 3 · 2015-06-17T06:12:13.340

0

2 Posibilities:--

Mostly your inventory object reference is null
your if code--

if (c.getModelYear()>= startYear && c.getModelYear()<= endYear)

Try below if instead above --

if(((c.getModelYear()!=null)?c.getModelYear():0)>=startYear&&
        c.getModelYear()<= endYear)

I am Assusming you have some proper value in 'startYear' and 'endYear' apart from Zero.

edited Jun 17 '15 at 06:12

answered Jun 17 '15 at 05:52

Ashish Patil

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score 0 · Answer 4 · answered Jun 17 '15 at 06:33

if you can use java 8 the following code should work:

if(inventory==null){
        return 0;
}
return inventory.stream().filter((Lamborghini c)-> c!=null && c.getModelYear()>= startYear && c.getModelYear()<= endYear).count();

but without you telling us WHERE exactly the nullpointer is happening, it's just a shot in the dark.

score 0 · Answer 5 · answered Jun 17 '15 at 07:00

You don't two ifs. because "for" loop will only continue for each c value.

public int howManyBetweenTheseYears(int startYear, int endYear)
{
    ArrayList<Lamborghini> selectedCars = new ArrayList<Lamborghini>();

    for(Lamborghini c : inventory)
    {       
        if(c.getModelYear()>= startYear && c.getModelYear()<= endYear)
        {
            selectedCars.add(c);
        }
    }
    return selectedCars.size();
 }

Also have a variable that holds the return value and initiate it by giving size 0. else it will give you nullpointerexception if can't find any matching car.

score 0 · Accepted Answer · answered Jul 09 '15 at 08:13

sorry i couldn't reply to any of you, and I realized the code I left was not compete, but i finally figured out what was wrong, it doesn't make sense to me but it did fix the problem, and the problem wasn't even in the method i posted.

originally I had (ArrayList Lamborghini) when i was initializing the inventory arraylist:

public class LamborghiniCarLot
{
private String lotName;
private ArrayList<Lamborghini> inventory;

public LamborghiniCarLot()
{
 ArrayList<Lamborghini> inventory = new ArrayList<Lamborghini>();
}

public LamborghiniCarLot(String lotName){
  ArrayList<Lamborghini>inventory = new ArrayList<Lamborghini>();
    setLotName(lotName);

then I tried to remove the (ArrayList Lamborghini) before inventory and it fixed everything:

public LamborghiniCarLot()
{
    inventory = new ArrayList<Lamborghini>();
}

public LamborghiniCarLot(String lotName){
    inventory = new ArrayList<Lamborghini>();
    setLotName(lotName);

It would be appreciated if someone can explain to me what that changed and why it wouldn't work with arraylist lamborghini before inventory. I am new to programming so please be detailed.

for-each loop NullPointerException

6 Answers6