CODEWITHSUNDEEP
javaarraylistprimitive
BNetz
BNetz

Reputation: 361

Java ArrayList: Adding primitive type or its wrapper-class: What's the difference?

imagine the following ArrayList in Java:

ArrayList<Integer> u = new ArrayList<Integer>();

I want to know if there is a difference when adding new values either as primitive types or as wrapper-classes:

u.add(new Integer(12));
u.add(12);

Thanks in advance!

Upvotes: 0

Views: 2604

Answers (2)

Cratylus
Cratylus

Reputation: 54074

There is no difference in add due to auto boxing/unboxing. Actually don't do new Integer(12) but Integer.valueOf(12) since it uses the flighweight pattern and reuses known objects (in the range -128, 127). So no new object would be created.

There is a difference in remove for example.
Since if you intent to call remove(Object) calling remove(5) will call remove(int index) and this perhaps is not what you want.
You should do remove((Integer)5) if you want to remove the number 5 or remove(5) if you want to remove the fifth element.

Upvotes: 8

Nazarii Bardiuk
Nazarii Bardiuk

Reputation: 4342

When you do u.add(12); compiler rewrites it to u.add(Integer.valueOf(12)); which is more efficient than u.add(new Integer(12)); Read more on official tutorial http://docs.oracle.com/javase/tutorial/java/data/autoboxing.html

Upvotes: 7

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