Only functional interfaces can use the lambda feature in Java. Abstract classes with only one abstract method cannot use lambdas. Can’t have constructor. Can have constructor.

An abstract class can declare fields, constructors, and non-abstract methods in addition to or instead of abstract methods. For example, an abstract Vehicle class might declare fields describing ...

Constructors play a key role in all object-oriented programming languages, and Java is no exception. Every class a Java developer creates needs a constructor. Constructors perform numerous important ...