How to avoid possible Null Pointer deference

Question

I have made a simple add method that takes two args. Here is the code :

public List<myListType> add(List<myListType> myTypes, myListType myType) {
    if (myTypes == null) {
        myTypes = new ArrayList<myListType>();
    }

    int size = myTypes.size();

    if (size > 1) {

        Boolean lastStatus = myTypes.get(myTypes.size()-1).getAvailabilityStatus();

        Boolean secondLastElement = myTypes.get(myTypes.size() - 2).getAvailabilityStatus();
        if (lastStatus == null && secondLastElement == null) {
            myTypes.remove(myTypes.size()-1);
        }
        else if (lastStatus.equals(secondLastElement)) {

            myTypes.remove(myTypes.size()-1);
        }
    }

    myTypes.add(myType);

    return myTypes;
}

I think there is actually a possible null pointer deference in the if condition, especially on lastStatus. Do you see something I can do in order to avoid that ?

Thanks.

Answer 1

Assuming you're using java 7+, you can use Objects.equals, which takes care of both your conditions:

Boolean secondLastElement = myTypes.get(myTypes.size() - 2).getAvailabilityStatus();
if (Objects.equals(lastStatus, secondLastElement)) {
    myTypes.remove(myTypes.size()-1);
}