Why are most of the examples using ArrayList

Question

Developing Java, you have always learned that its best to create an ArrayList by using the List interface as the type for the variable the list is stored in. Like this

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

However, by looking at a lot of the android examples that is included in the bundle, they have created the list by using the Class.

ArrayList<String> myList = new ArrayList<String>();

Is there any reason why this is done? Is it faster, lighter or something to explicitly setting the Class?

Answer 1

I'd recommend to read Performance Myths, which explains which are the advantages and problems of defining a variable as List or ArrayList.

Answer 2

Personally, I believe that the thing "you have always learned" misses the point. This:

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

has very little maintenance benefit. If you want to change it to a different implementation, it's still only one line to change if you use the implementation type. However, a totally different matter is this:

public void process(List<String> list) {

Here, using the interface really matters because it allows people who call the method to use different implementations without having to change the method signature (which they may not be able to do).