Why is it that in Java often make list judgment, not only to judge the list is not NULL, but also to judge size>0 it, is not superfluous it?

List list=new ArrayList ();
1. If this is the case, LIS is not null but size=0

Such a collection for subsequent judgments is useless, or even reported anomalies, such as List.get (0.......N) such as the value of judgment, will be reported abnormal.

2. If you first judge the size and then judge null such as:
if (list.size>0) {};
In this case, if the list equals null then List.size will report a null pointer exception

So to double judgment so write best if (list!=null && list.size>0) {};

Why is it that in Java often make list judgment, not only to judge the list is not NULL, but also to judge size>0 it, is not superfluous it?