Java and OOP

What is the purpose of the super() keyword in Java?

• It refers to the current object

• It is used to call a superclass constructor or method

• It creates a superclass object

• It returns the superclass type

Which of the following is true about Java inheritance?

• A) A class can inherit from multiple classes

• B) A subclass can access private members of its superclass

• C) Inheritance helps avoid redundancy and promotes code reuse

• D) Java supports multiple inheritance

What is polymorphism in OOP?

• The ability to define methods with different signatures in the same class

• The ability for a method in a subclass to override a method in its superclass

• The ability to assign different objects to a reference variable of a superclass type

• The ability to use the same method name in a class with different return types

Which of the following is an example of encapsulation in Java?

• Declaring all data members as private and providing public getter and setter methods

• Using the super keyword to call a superclass method

• Declaring multiple classes in a single file

• Overriding a method in the subclass

In Java, what happens if you do not explicitly call a superclass constructor?

• The default constructor of the superclass is called automatically.

• The subclass constructor fails to compile.

• No constructor is called, and the object is not created.

• The JVM throws a runtime exception.

What happens if a subclass constructor does not explicitly call a superclass constructor in Java?

• The subclass constructor will automatically call the superclass constructor

• The program will throw an error

• The subclass constructor must always call a superclass constructor explicitly

• Java will call the this() constructor for the subclass

What is the main difference between method overloading and method overriding?

• Overloading happens at runtime, while overriding happens at compile-time

• Overloading involves different signatures, and overriding involves the same signature in both parent and subclass

• Overloading is used for constructors, and overriding is used for methods

• Overloading is when the parent method is hidden by the subclass method

What does the final keyword do in Java?

• It defines a method that cannot be overridden

• It defines a class that cannot be extended

• It defines a variable whose value cannot be changed

• All of the above

Which of the following is true about abstract classes in Java?

• An abstract class can have no methods

• An abstract class cannot have constructors

• A class can inherit multiple abstract classes

• An abstract class can have both abstract and non-abstract methods

What is the purpose of the toString() method in Java?