Assigning ArrayList to List

Question

Is there any Difference between two lines in the following

 ArrayList<String> arrName =  new ArrayList<String>();
 List<String>      arrName =  new ArrayList<String>();

Thanks for Reply

I've seen the same question (even same text) between yesterday and today (but can't find it). — Luiggi Mendoza, Feb 20 '13 at 07:51
Explanation [here](http://stackoverflow.com/questions/4062982/java-oop-list-versus-arraylist-as-reference-type) — PbxMan, Feb 20 '13 at 07:54
Wow, 6 answer so far, and 3 people there can vote to close the question as duplicate. — Luiggi Mendoza, Feb 20 '13 at 07:57

score 4 · Accepted Answer · answered Feb 20 '13 at 07:51

Almost always the second one is preferred over the first one. The second has the advantage that the implementation of the List can change (to a LinkedList for example), without affecting the rest of the code. This is will be difficult to do with an ArrayList, not only because you will need to change ArrayList to LinkedList everywhere, but also because you may have used ArrayList specific methods.

score 3 · Answer 2 · edited May 23 '17 at 12:31

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Try to hide specific implementation behind an Interface whenever possible. see this

edited May 23 '17 at 12:31

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answered Feb 20 '13 at 07:54

D.S

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score 2 · Answer 3 · edited May 23 '17 at 10:28

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The latter is usually recommended as long as you only need a List interface later on. That's called "programming to interface, not implementation".

As for the detailed difference between them, I have answered in another question on stackoverflow: The difference between "C c = new C()" and "A c = new C()" when C is a subclass of A in Java

edited May 23 '17 at 10:28

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answered Feb 20 '13 at 07:50

Hui Zheng

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score 2 · Answer 4 · answered Feb 20 '13 at 07:50

The second approach is usually the preferred one as it hides the implementation behind an interface.

This means that later on, if the requirements will change and will require another implementation of the List interface, you can change just one line of code and everything else will still work because you were coding to an interface not to a class.

score 2 · Answer 5 · answered Feb 20 '13 at 07:53

There is not much difference per se, but List shall be used whenever possible as it is an interface and you may see in standard libraries' methods parameters are generally List<K>, so that any specific implementation can be passed, like ArrayList or LinkedList.

score 2 · Answer 6 · edited May 23 '17 at 10:28

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Second is example of Program to Interface and its the preferred way.
For details What does it mean to "program to an interface"?

edited May 23 '17 at 10:28

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answered Feb 20 '13 at 07:55

Ajinkya

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Assigning ArrayList to List

6 Answers6

Linked