AP Computer Science A 100& Correct
What is encapsulation in object-oriented programming?
✔✔ Encapsulation is the concept of bundling data (fields) and methods (functions) that operate
on the data into a single unit, typically a class. It helps to protect the internal state of an object
and exposes only necessary parts through public methods.
What does inheritance allow you to do in Java?
✔✔ Inheritance allows a subclass to inherit fields and methods from a superclass. This promotes
code reusability and establishes a hierarchical relationship between classes.
What is polymorphism, and how is it used in Java?
✔✔ Polymorphism allows objects of different classes to be treated as objects of a common
superclass. It enables method overriding, where a subclass provides a specific implementation of
a method that is already defined in its superclass.
What is abstraction, and why is it important?
1
,✔✔ Abstraction is the practice of hiding the complex implementation details of a system and
exposing only the essential features. It simplifies interaction with complex systems and helps in
managing and reducing complexity.
What is the purpose of a constructor in Java?
✔✔ A constructor is a special method used to initialize objects. It is called when an instance of a
class is created and can be used to set initial values for object attributes.
What does the `static` keyword signify in Java?
✔✔ The `static` keyword defines class-level methods and variables that belong to the class rather
than any specific instance. Static members are shared among all instances of the class and can be
accessed without creating an instance.
What is the role of the `this` keyword in Java?
2
,✔✔ The `this` keyword refers to the current instance of the class. It is used to distinguish
instance variables from parameters and to invoke other constructors or methods within the same
class.
What is the purpose of the `super` keyword?
✔✔ The `super` keyword is used to call the parent class's constructor or methods from a
subclass. It allows a subclass to access inherited members that are overridden or hidden.
What is method overloading, and how does it differ from method overriding?
✔✔ Method overloading is the practice of defining multiple methods with the same name but
different parameter lists within the same class. Method overriding occurs when a subclass
provides a specific implementation of a method that is already defined in its superclass.
What is an interface in Java, and how is it used?
3
, ✔✔ An interface in Java is a reference type that defines a contract of methods that implementing
classes must provide. It is used to achieve abstraction and multiple inheritance of method
signatures.
What does the `final` keyword do in Java?
✔✔ The `final` keyword can be used to define constants, prevent method overriding, and prevent
inheritance of a class. It signifies that the value or behavior cannot be changed after initialization.
What is the difference between an `ArrayList` and an array in Java?
✔✔ An `ArrayList` is a dynamic data structure that can grow or shrink in size, while an array is
a fixed-size data structure with a constant length once initialized. `ArrayList` provides more
flexibility with methods for adding, removing, and accessing elements.
What is the role of the `instanceof` operator in Java?
✔✔ The `instanceof` operator checks whether an object is an instance of a specific class or
subclass. It is used to verify the type of an object at runtime.
4
What is encapsulation in object-oriented programming?
✔✔ Encapsulation is the concept of bundling data (fields) and methods (functions) that operate
on the data into a single unit, typically a class. It helps to protect the internal state of an object
and exposes only necessary parts through public methods.
What does inheritance allow you to do in Java?
✔✔ Inheritance allows a subclass to inherit fields and methods from a superclass. This promotes
code reusability and establishes a hierarchical relationship between classes.
What is polymorphism, and how is it used in Java?
✔✔ Polymorphism allows objects of different classes to be treated as objects of a common
superclass. It enables method overriding, where a subclass provides a specific implementation of
a method that is already defined in its superclass.
What is abstraction, and why is it important?
1
,✔✔ Abstraction is the practice of hiding the complex implementation details of a system and
exposing only the essential features. It simplifies interaction with complex systems and helps in
managing and reducing complexity.
What is the purpose of a constructor in Java?
✔✔ A constructor is a special method used to initialize objects. It is called when an instance of a
class is created and can be used to set initial values for object attributes.
What does the `static` keyword signify in Java?
✔✔ The `static` keyword defines class-level methods and variables that belong to the class rather
than any specific instance. Static members are shared among all instances of the class and can be
accessed without creating an instance.
What is the role of the `this` keyword in Java?
2
,✔✔ The `this` keyword refers to the current instance of the class. It is used to distinguish
instance variables from parameters and to invoke other constructors or methods within the same
class.
What is the purpose of the `super` keyword?
✔✔ The `super` keyword is used to call the parent class's constructor or methods from a
subclass. It allows a subclass to access inherited members that are overridden or hidden.
What is method overloading, and how does it differ from method overriding?
✔✔ Method overloading is the practice of defining multiple methods with the same name but
different parameter lists within the same class. Method overriding occurs when a subclass
provides a specific implementation of a method that is already defined in its superclass.
What is an interface in Java, and how is it used?
3
, ✔✔ An interface in Java is a reference type that defines a contract of methods that implementing
classes must provide. It is used to achieve abstraction and multiple inheritance of method
signatures.
What does the `final` keyword do in Java?
✔✔ The `final` keyword can be used to define constants, prevent method overriding, and prevent
inheritance of a class. It signifies that the value or behavior cannot be changed after initialization.
What is the difference between an `ArrayList` and an array in Java?
✔✔ An `ArrayList` is a dynamic data structure that can grow or shrink in size, while an array is
a fixed-size data structure with a constant length once initialized. `ArrayList` provides more
flexibility with methods for adding, removing, and accessing elements.
What is the role of the `instanceof` operator in Java?
✔✔ The `instanceof` operator checks whether an object is an instance of a specific class or
subclass. It is used to verify the type of an object at runtime.
4
