Initialization of an ArrayList in one line

arraylist, collections, initialization, java

Solution

Actually, probably the "best" way to initialize the `ArrayList` is the method you wrote, as it does not need to create a new `List` in any way:

ArrayList<String> list = new ArrayList<String>();
list.add("A");
list.add("B");
list.add("C");

The catch is that there is quite a bit of typing required to refer to that `list` instance.

There are alternatives, such as making an anonymous inner class with an instance initializer (also known as an "double brace initialization"):

ArrayList<String> list = new ArrayList<String>() {{
    add("A");
    add("B");
    add("C");
}};

However, I'm not too fond of that method because what you end up with is a subclass of `ArrayList` which has an instance initializer, and that class is created just to create one object -- that just seems like a little bit overkill to me.

What would have been nice was if the Collection Literals proposal for Project Coin was accepted (it was slated to be introduced in Java 7, but it's not likely to be part of Java 8 either.):

List<String> list = ["A", "B", "C"];

Unfortunately it won't help you here, as it will initialize an immutable `List` rather than an `ArrayList`, and furthermore, it's not available yet, if it ever will be.

Problem

I wanted to create a list of options for testing purposes. At first, I did this: ``` ArrayList<String> places = new ArrayList<String>(); places.add("Buenos Aires"); places.add("Córdoba"); places.add("La Plata"); ``` Then, I refactored the code as follows: ``` ArrayList<String> places = new ArrayList<String>( Arrays.asList("Buenos Aires", "Córdoba", "La Plata")); ``` Is there a better way to do this?

Original source

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