All Flashcards
What are the differences between explicit and implicit calls to the superclass constructor?
Explicit: uses 'super()', programmer-defined arguments | Implicit: auto-inserted by Java, no-argument constructor
What are the differences between calling 'super()' with arguments and calling it without arguments?
With arguments: calls a specific superclass constructor with matching parameters | Without arguments: calls the no-argument constructor of the superclass
What are the differences between initializing instance variables in a superclass constructor vs. a subclass constructor?
Superclass: initializes inherited variables | Subclass: initializes variables specific to the subclass
What are the differences between the roles of the superclass and subclass constructors in object creation?
Superclass: initializes the inherited state and behavior. Subclass: Extends the superclass and initializes its own state and behavior.
What are the differences between the effects of calling 'super()' and not calling 'super()' in a subclass constructor?
Calling 'super()': ensures superclass initialization | Not calling 'super()': relies on implicit call to no-argument constructor (if it exists), may lead to errors if it doesn't exist.
What are the differences between how constructors are inherited vs. how methods are inherited?
Constructors: are not inherited, must be explicitly called using 'super()' | Methods: are inherited and can be overridden.
What are the differences between the purpose of a constructor in a superclass versus a subclass?
Superclass: initializes the common state of all its subclasses. Subclass: initializes its own state and potentially extends the superclass's state.
What are the differences between the flexibility of explicit vs. implicit superclass constructor calls?
Explicit: allows choosing which superclass constructor to call with specific arguments. Implicit: only calls the no-argument constructor.
What are the differences between the consequences of an exception thrown in a superclass constructor vs. a subclass constructor?
Superclass: can prevent the entire object from being created if not handled. Subclass: can be handled within the subclass, allowing partial object creation or alternative initialization.
What are the differences between the visibility of constructors in superclasses vs. subclasses?
Superclass: determines who can create instances of the superclass directly. Subclass: inherits visibility rules but can only call the superclass constructor through 'super()'.
Why are constructors not inherited?
Constructors are specific to the class they are defined in and are responsible for initializing objects of that class.
What is the purpose of the 'super' keyword in a subclass constructor?
To call the constructor of the superclass, allowing reuse of initialization logic.
What happens if a subclass constructor doesn't explicitly call a superclass constructor?
Java automatically inserts a call to the superclass's no-argument constructor.
Why is it important to call the superclass constructor in a subclass?
To ensure that the superclass's instance variables are properly initialized.
Explain the constructor call chain in Java.
Subclass constructor calls superclass constructor, which may call its superclass constructor, and so on, up to the Object class constructor.
What is the role of the Object class in the constructor call chain?
It is the ultimate superclass, and its constructor is always the first to be called.
How does the 'super' keyword promote code reuse?
It allows subclasses to leverage the initialization logic already defined in the superclass constructor.
What is the significance of calling 'super' as the first statement in a subclass constructor?
It ensures that the superclass is initialized before any subclass-specific initialization takes place.
Explain how instance variables are initialized in a subclass when using 'super'.
Instance variables of the superclass are initialized by the superclass constructor, and subclass-specific instance variables are initialized separately in the subclass constructor.
What is the impact of not properly initializing the superclass when creating a subclass?
It can lead to unexpected behavior or errors due to uninitialized or incorrectly initialized superclass members.
What is the definition of 'Superclass'?
A class from which other classes (subclasses) inherit attributes and methods.
What is the definition of 'Subclass'?
A class that inherits attributes and methods from another class (superclass).
What is the definition of the 'super' keyword?
A keyword used to call the superclass's constructor or access its members from the subclass.
What is the definition of 'Constructor'?
A special method used to initialize objects of a class.
What is the definition of 'Inheritance'?
A mechanism where a class acquires the properties (attributes and methods) of another class.
What is the definition of 'No-argument constructor'?
A constructor that takes no arguments.
What is the definition of 'Explicit constructor call'?
A constructor call made directly in the code, using the 'super' keyword.
What is the definition of 'Implicit constructor call'?
A constructor call automatically inserted by the compiler when no explicit call is made.
What is the definition of 'Object class'?
The ultimate superclass of all classes in Java.
What is the definition of 'Instance variable'?
A variable defined in a class (i.e., a member variable) for which every object of the class has its own copy.