Urgent Help Required!!!

Hi bellow is most of a class I coded, I'm having problems retrieving the planeIdNo from the object array list. I get a NullPointerError. I can access the list in the addPlane method and retrieve the planeIdNo or planeSize but not in findPlane why is this am I doing somthing wrong, I'm new to OOP.

Code:

---

public class RegisteredList
{
    Airplane list[];
    int total = 0;

    //--------------------------------------------------------------------------

    public RegisteredList(int maxPlanes)
    {
        list = new Airplane[maxPlanes];
    }

    //--------------------------------------------------------------------------

    public int addPlane(Airplane planeToAdd) throws IOException
    {
        if (isFull() == true)
        {
            return -1;
        }

        if (isInList(planeToAdd.getIdNo()) == true)
        {
            return 0;
        }

        list[total] = planeToAdd;
        total++;

        return 1;
    }

    //--------------------------------------------------------------------------

    public Airplane findPlane(String planeId) throws IOException
    {
        for (int i = 0; i < list.length; i++)
        {
            try
            {
                if (list[i].getIdNo() == planeId)
                {
                    return list[i]; // plane found
                }
            }

            catch( NullPointerException npe)
            {
                // do nothing
            }
        }

        return null; // plane not found
    }

    //--------------------------------------------------------------------------

    public boolean isInList(String planeId) throws IOException
    {
        if (findPlane(planeId) != null)
        {
            return true; // plane is in list
        }

        return false; // plane is not in list
    }

    //--------------------------------------------------------------------------
}

---

Here is the Airplane class

Code:

---

public class Airplane
{
    String idNo;
    int size;

    //--------------------------------------------------------------------------

    public Airplane(String planeId, int planeSize)
    {
        idNo = planeId;
        size = planeSize;
    }

    //--------------------------------------------------------------------------

    public String getIdNo()
    {
        return idNo;
    }

    //--------------------------------------------------------------------------

    public int getSize()
    {
        return size;
    }
}

//------------------------------------------------------------------------------

---

If your require further explanation please ask.

Just scanning your code, I didn't see each/any element of list[] being initialized with
list[anIndex] = new Airplane(aPlaneId, aPlaneSize);
If you don't, list[anIndex] will be null although list.length is valid.

Also, instead of
if (list[i].getIdNo() == planeId)
you'll want to use
if (list[i].getIdNo().equals(planeId))

VirtuallyVB thanks for your help really appreciate it!!!

I did however have the list[anIndex] = new Airplane("", 0); in the constructor before and can't rember why I took it out, any way I added that in there again and added/changed code here and ther and managed to get it working, I think one of the main thing was that I == instead of the equals() function, thanks again!!!