Why is the Arrays.asList () method needed? What is its essence?

Answer 1, authority 100%

As follows from documentation : Builds a list based on an array. The array is then used for the internal representation of the list. This preserves the link between the list and the original array:

• changes to the array will be reflected in the list:

  String [] a = {"foo", "bar", "baz"};
  List & lt; String & gt; list = Arrays.asList (a);
  System.out.println (list); // [foo, bar, baz]
  a [0] = "aaa";
  System.out.println (list); // [aaa, bar, baz]
  

• changes in the list will be reflected in the array:

  String [] a = {"foo", "bar", "baz"};
  List & lt; String & gt; list = Arrays.asList (a);
  System.out.println (list); // [foo, bar, baz]
  list.set (0, "bbb");
  System.out.println (Arrays.toString (a)); // [bbb, bar, baz]
  

If the array contains objects, obviously both the array and the list will refer to the same instances:

Object [] a = {new Object (), new Object (), new Object ()};
List & lt; Object & gt; list = Arrays.asList (a);
System.out.println (a [0] == list.get (0)); // true

As already mentioned by @Oleg Chiruhin , the fact that the method takes an array as a parameter in the form of variable length arguments allows it to be used for relatively convenient initialization of lists:

List & lt; Foo & gt; list = Arrays.asList (new Foo (...), new Foo (...), new Foo (...));

compare with

List & lt; Foo & gt; list1 = new ArrayList & lt; & gt; ();
list.add (new Foo (...));
list.add (new Foo (...));
list.add (new Foo (...));

Answer 2, authority 53%

In addition to what is described in the JavaDoc, the practical essence of this method is that quite often you need to send a list to the method input, the elements of which are known in advance (for example, some set of magic constants, which is often required to quickly write TDD -tests). But there is no pretty syntax in Java for initializing an in-place list, right at the place of the call. Therefore, you can call it simply in the syntax mymethod (Arrays.asList ("Novosibirsk", "Moscow", "Kukuevo")) . Note that I was able to initialize the sheet even inside a sentence in Russian!