Collecting Objects - Beginning Java 7 - page 521

@Override
public String toString()
{
return birds.toString();
}
}
class EmptyListDemo
{
public static void main(String[] args)
{
Birds birds = new Birds();
System.out.println(birds);
birds = new Birds("Swallow", "Robin", "Bluejay",
"Oriole");
System.out.println(birds);
}
}
Listing 5-26 declares a Birds class that stores the names of various birds in a list.
This class provides two constructors, a noargument constructor and a constructor that
takes a variable number of String arguments identifying various birds.
Thenoargumentconstructorinvokes emptyList() toinitializeitsprivate birds
fieldtoanempty List of String — emptyList() isagenericmethodandthecom-
piler infers its return type from its context.
If you're wondering about the need for emptyList() , look at the toString()
method.Noticethatthismethodevaluates birds.toString() .Ifwedidnotassign
areferencetoanempty List<String> to birds , birds wouldcontain null (the
default value for this instance field when the object is created), and a NullPoint-
erException instance would be thrown when attempting to evaluate
birds.toString() .
Whenyourunthisapplication( java EmptyListDemo ),itgeneratesthefollowing
output:
[]
[Swallow, Robin, Bluejay, Oriole]