Are there any major disadvantages of initializing a Java collection, e.g. ArrayList at the time of declaration such as :
List<String> strList = new ArrayList<String>();
The main purpose is to avoid the clutter of null checks while retrieving the elements.
Thanks
In general, the only disadvantage is that you may end up with a whole bunch of collections doing nothing and have unnecessarily done work to create the collection.
My personal preference is to assign a valid collection always unless there's a definite reason to avoid the memory and initialization overhead, such as within loops and other possible performance considerations. And if I was always ensuring the objects were initialized to non-null I would not then do redundant null-checks before using the collections.
The caution I would add is to make sure if you do use the collection that you use it and don't, in later code, replace it with an entirely new collection (that would indicate a probable design flaw). To enforce this you can declare the collection as final.
final as well. Then you know it's initialized and never null.
It depends on the use case:
null. In the first case I make it final and prefer initializing in a constructor. If it might be null, I add a lazy getter and annotate it with @Nullable like this: @Nullable
List<String> strList;
...
public final List getList(){
if(strList == null){
strList = new ArrayList();
}
return strList;
}
This technique helps me to eliminate ambiguity of field states.
You should almost always initialize right away. Just because it's initialized doesnt mean you shouldnt do null checks anymore. Creating the object and an if check have almost no effect on performance. Only when you're creating a list that has to copy objects from other collections or arrays
