Understanding Java Classes and Inheritance

What is the difference between a subclass and a superclass?

• A subclass inherits from a superclass, allowing for specialization and reuse of code.

• A superclass cannot have subclasses.

• A subclass is a type of superclass.

• A subclass is always more complex than a superclass.

Explain the substitution principle in Java.

• The substitution principle only applies to interfaces in Java.

• Substituting a subclass for a superclass always leads to runtime errors.

• The substitution principle in Java allows subclasses to be used in place of their superclass without altering the desired behavior of the program.

• Subclasses cannot override methods from their superclass.

What is polymorphism and how is it achieved in Java?

• Polymorphism is the ability to create multiple classes in Java.

• Polymorphism is achieved through the use of interfaces only.

• Polymorphism allows objects to be created without any methods.

• Polymorphism is the ability of an object to take on many forms, achieved in Java through method overriding and method overloading.

How do you declare a subclass in Java?

• class SubclassName extends SuperclassName {

• class SubclassName implements SuperclassName {

• class SubclassName inherits SuperclassName {

• class SubclassName extends SuperclassName() {

What does the 'extends' keyword signify in Java?

• The 'extends' keyword is for defining interfaces in Java.

• The 'extends' keyword signifies inheritance in Java.

• The 'extends' keyword indicates a static class in Java.

• The 'extends' keyword is used for method overloading in Java.

Can a subclass have instance variables that are not in the superclass?

• A subclass can only inherit instance variables from the superclass.

• Yes, a subclass can have instance variables that are not in the superclass.

• A subclass must have the same instance variables as the superclass.

• No, a subclass cannot have any instance variables.

How can a subclass access the constructors of its superclass?

• A subclass must redefine all superclass constructors.

• A subclass accesses superclass constructors using the 'this' keyword.

• A subclass can only use its own constructors.

• A subclass accesses superclass constructors using the 'super' keyword.

What is the purpose of the 'super' keyword in Java?

• To define a new class in Java.

• To create a static method in the parent class.

• To access methods and constructors of the parent class.

• To override methods in the child class.

How do you override a method in a subclass?

• Use a different return type in the subclass method.

• Change the method name in the subclass.

• Add additional parameters to the subclass method.

• Define a method in the subclass with the same name and parameters as the superclass method.

What is the syntax to call a method from the superclass in a subclass?

• call.methodName()

• super.methodName()

• parent.methodName()

• this.methodName()