Which of the following statements regarding abstract methods in Java are true? You may need to select more than one answer.

1. An abstract class can have instances created using the constructor of the abstract class.

2.An abstract class can be extended. A subclass of a non-abstract superclass can be abstract.

3. A subclass can override a concrete method in a superclass to declare it abstract.

4. An abstract class can be used as a data type.