Data Structures and Algorithms in Java Exam Questions with Verified Solutions Graded A+
Public, private, protected - Answers Private: only the class in which it is declared can see it; Protected:
can only be seen and used by the package in which it was declared and can be seen by subclasses or
package members; Public: Everyone can see it
Different types of loops - Answers For, while, if
What is inheritance? - Answers Inheritance is a mechanism in which one object acquires all the
properties and behavior of another object of another class. It represents IS-A relationship. It is used for
Code Reusability and Method Overriding.
What does super mean? - Answers A reference variable that is used to refer parent class objects. Used in
derived classes. Used to call parent methods. Used to access parent class constructor.
What does static mean? - Answers variable or function is shared between all instances of that class.
Belongs to the type, not the actual objects themselves
What is an anonymous class? Why can't we write a constructor for an anonymous class? - Answers An
anonymous class is a local class without a name. It is defined and instantiated in a single succinct
expression using the 'new' operator. Since an anonymous class has no name it's not possible to write a
constructor. We must instead use a local class or an instance initializer.
How to write a class that implements an interface - Answers public class X implements YInterface
What is a set? - Answers A set is a standard generic data type that uses an array data structure.
Collection extends set.
What is a linked list? - Answers A linear data structure with a node class that has nodes connected by
pointers. Linked lists should have iterators
What are instance variables? - Answers An instance variable is a variable which is related to a single
instance of a class. Each time an instance of a class is created, the system creates one copy of the
instance variables related to that class. An instance variable is declared inside a class, but not within a
method. A variable which is defined inside a class and a method is known as a local variable. The
opposite of an instance variable is a static variable. A static variable exists across instances of a class. By
default, all variables are created as instance variables.
What is a constructor? - Answers This is a special method used to instantiate objects of a particular class.
It is used in conjunction with the new operator. It initializes an object immediately upon creation. Once
defined, it is called immediately after the object is created. When a new instance of the class is created,
the constructor is called.
What are the four principles of object oriented programming? - Answers Abstraction, encapsulation,
inheritance, polymorphism
Public, private, protected - Answers Private: only the class in which it is declared can see it; Protected:
can only be seen and used by the package in which it was declared and can be seen by subclasses or
package members; Public: Everyone can see it
Different types of loops - Answers For, while, if
What is inheritance? - Answers Inheritance is a mechanism in which one object acquires all the
properties and behavior of another object of another class. It represents IS-A relationship. It is used for
Code Reusability and Method Overriding.
What does super mean? - Answers A reference variable that is used to refer parent class objects. Used in
derived classes. Used to call parent methods. Used to access parent class constructor.
What does static mean? - Answers variable or function is shared between all instances of that class.
Belongs to the type, not the actual objects themselves
What is an anonymous class? Why can't we write a constructor for an anonymous class? - Answers An
anonymous class is a local class without a name. It is defined and instantiated in a single succinct
expression using the 'new' operator. Since an anonymous class has no name it's not possible to write a
constructor. We must instead use a local class or an instance initializer.
How to write a class that implements an interface - Answers public class X implements YInterface
What is a set? - Answers A set is a standard generic data type that uses an array data structure.
Collection extends set.
What is a linked list? - Answers A linear data structure with a node class that has nodes connected by
pointers. Linked lists should have iterators
What are instance variables? - Answers An instance variable is a variable which is related to a single
instance of a class. Each time an instance of a class is created, the system creates one copy of the
instance variables related to that class. An instance variable is declared inside a class, but not within a
method. A variable which is defined inside a class and a method is known as a local variable. The
opposite of an instance variable is a static variable. A static variable exists across instances of a class. By
default, all variables are created as instance variables.
What is a constructor? - Answers This is a special method used to instantiate objects of a particular class.
It is used in conjunction with the new operator. It initializes an object immediately upon creation. Once
defined, it is called immediately after the object is created. When a new instance of the class is created,
the constructor is called.
What are the four principles of object oriented programming? - Answers Abstraction, encapsulation,
inheritance, polymorphism
