Identify the error in this Java code:

Identify the error in this Java code:

abstract class Animal {
  abstract void sound();
}
class Dog extends Animal {
  void sound() {
    System.out.println("Bark");
  }
}
class Cat extends Animal {
  void sound() {
    System.out.println("Meow");
  }
}
public class Test {
  public static void main(String[] args) {
    Animal a = new Animal();
    a.sound();
  }
}