How does Arrays.asList(T... a) return an interface?

Question

I am looking at the Java API from Oracle, particularly at this method that is part of the java.util.Arrays class:

public static <T> List<T> asList(T... a)

But how is it possible that this method is returning a List object when clearly it is an interface?

Answer 1

• It is called polymorphism
• It means you can refer to a subtype using supertype reference
• In this case, the method is returning instances of class that implement the List interface

Source code of Arrays.asList method

 public static <T> List<T> More ...asList(T... a) {
   return new ArrayList<T>(a);
}