Object-Oriented Programming, unit: Abstract Classes and Interfaces. Core concepts, terminology, and worked-example cues a college student meets for this unit, building on prior units without repeating them. Front: a term, concept, or short problem cue. Back: the definition, explanation, or answer.
13 cards · basic cards · AI-written, checked twice. Edit anything.
- What is an abstract class?
- A class that cannot be instantiated directly and may contain unimplemented methods
- What is an abstract method?
- A method declared without an implementation, requiring subclasses to define it
- Why would a class be declared abstract?
- To define a common structure while forcing subclasses to provide specific behavior
- What is an interface, in OOP?
- A contract defining method signatures that implementing classes must provide
- What is the main difference between an abstract class and an interface?
- An abstract class can include shared implementation; an interface traditionally only declares method signatures
- Can a class implement multiple interfaces?
- Yes, a class can implement any number of interfaces
- Can a class extend multiple abstract classes (in most single-inheritance languages)?
- No, typically only one class can be extended, but multiple interfaces can be implemented
- What is a default method in an interface?
- A method with a provided implementation that implementing classes may optionally override
- What is a marker interface?
- An interface with no methods, used to tag a class with a particular property
- Why use an interface instead of a concrete class as a type?
- It allows code to depend on behavior rather than a specific implementation, improving flexibility
- What is programming to an interface, as a design principle?
- Writing code that depends on abstract behavior rather than concrete implementations
- What happens if a class fails to implement all abstract methods of an interface?
- The class must itself be declared abstract, or a compile error occurs
- What is an abstract class's constructor used for, even though it cannot be instantiated?
- Initializing shared state that subclasses inherit when they are instantiated
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