Java Interview Exam Questions Answered Correctly Graded A+
What are Encapsulation, Inheritance and Polymorphism? - Answers Encapsulation is the mechanism that
binds together code and data it manipulates and keeps both safe from outside interference and misuse.
Inheritance is the process by which one object acquires the properties of another object. Polymorphism
is the feature that allows one interface to be used for general class actions.
What is the difference between Assignment and Initialization? - Answers Assignment can be done as
many times as desired whereas initialization can be done only once.
What is OOPs? - Answers Object oriented programming organizes a program around its data, i. e. ,
objects and a set of well defined interfaces to that data. An object-oriented program can be
characterized as data controlling access to code.
What are Class, Constructor and Primitive data types? - Answers Class is a template for multiple objects
with similar features and it is a blue print for objects. It defines a type of object according to the data the
object can hold and the operations the object can perform. Constructor is a special kind of method that
determines how an object is initialized when created. Primitive data types are 8 types and they are:
byte, short, int, long, float, double, boolean, char.
What is an Object and how do you allocate memory to it? - Answers Object is an instance of a class and
it is a software unit that combines a structured set of data with a set of operations for inspecting and
manipulating that data. When an object is created using new operator, memory is allocated to it.
What is the difference between constructor and method? - Answers Constructor will be automatically
invoked when an object is created whereas method has to be called explicitly.
What are methods and how are they defined? - Answers Methods are functions that operate on
instances of classes in which they are defined. Objects can communicate with each other using methods
and can call methods in other classes. Method definition has four parts. They are name of the method,
type of object or primitive type the method returns, a list of parameters and the body of the method. A
method's signature is a combination of the first three parts mentioned above.
What is the use of bin and lib in JDK? - Answers Bin contains all tools such as javac, appletviewer, awt
tool, etc., whereas lib contains API and all packages.
What is casting? - Answers Casting is used to convert the value of one type to another.
How many ways can an argument be passed to a subroutine and explain them? - Answers An argument
can be passed in two ways. They are passing by value and passing by reference. Passing by value: This
method copies the value of an argument into the formal parameter of the subroutine. Passing by
reference: In this method, a reference to an argument (not the value of the argument) is passed to the
parameter.
, What is the difference between an argument and a parameter? - Answers While defining method,
variables passed in the method are called parameters. While using those methods, values passed to
those variables are called arguments.
What are different types of access modifiers? - Answers public: Any thing declared as public can be
accessed from anywhere. private: Any thing declared as private can't be seen outside of its class.
protected: Any thing declared as protected can be accessed by classes in the same package and
subclasses in the other packages. default modifier : Can be accessed only to classes in the same package.
What is final, finalize() and finally? - Answers final : final keyword can be used for class, method and
variables. A final class cannot be subclassed and it prevents other programmers from subclassing a
secure class to invoke insecure methods. A final method can't be overridden. A final variable can't
change from its initialized value. finalize() : finalize() method is used just before an object is destroyed
and can be called just prior to garbage collection. finally : finally, a key word used in exception handling,
creates a block of code that will be executed after a try/catch block has completed and before the code
following the try/catch block. The finally block will execute whether or not an exception is thrown. For
example, if a method opens a file upon exit, then you will not want the code that closes the file to be
bypassed by the exception-handling mechanism. This finally keyword is designed to address this
contingency.
What is UNICODE? - Answers Unicode is used for internal representation of characters and strings and it
uses 16 bits to represent each other.
What is Garbage Collection and how to call it explicitly? - Answers When an object is no longer referred
to by any variable, java automatically reclaims memory used by that object. This is known as garbage
collection. System. gc() method may be used to call it explicitly.
What is finalize() method? - Answers finalize () method is used just before an object is destroyed and can
be called just prior to garbage collection.
What are Transient and Volatile Modifiers? - Answers Transient: The transient modifier applies to
variables only and it is not stored as part of its object's Persistent state. Transient variables are not
serialized. Volatile: Volatile modifier applies to variables only and it tells the compiler that the variable
modified by volatile can be changed unexpectedly by other parts of the program.
What is method overloading and method overriding? - Answers Method overloading: When a method in
a class having the same method name with different arguments is said to be method overloading.
Method overriding : When a method in a class having the same method name with same arguments is
said to be method overriding.
What is difference between overloading and overriding? - Answers a) In overloading, there is a
relationship between methods available in the same class whereas in overriding, there is relationship
between a superclass method and subclass method. b) Overloading does not block inheritance from the
superclass whereas overriding blocks inheritance from the superclass. c) In overloading, separate
What are Encapsulation, Inheritance and Polymorphism? - Answers Encapsulation is the mechanism that
binds together code and data it manipulates and keeps both safe from outside interference and misuse.
Inheritance is the process by which one object acquires the properties of another object. Polymorphism
is the feature that allows one interface to be used for general class actions.
What is the difference between Assignment and Initialization? - Answers Assignment can be done as
many times as desired whereas initialization can be done only once.
What is OOPs? - Answers Object oriented programming organizes a program around its data, i. e. ,
objects and a set of well defined interfaces to that data. An object-oriented program can be
characterized as data controlling access to code.
What are Class, Constructor and Primitive data types? - Answers Class is a template for multiple objects
with similar features and it is a blue print for objects. It defines a type of object according to the data the
object can hold and the operations the object can perform. Constructor is a special kind of method that
determines how an object is initialized when created. Primitive data types are 8 types and they are:
byte, short, int, long, float, double, boolean, char.
What is an Object and how do you allocate memory to it? - Answers Object is an instance of a class and
it is a software unit that combines a structured set of data with a set of operations for inspecting and
manipulating that data. When an object is created using new operator, memory is allocated to it.
What is the difference between constructor and method? - Answers Constructor will be automatically
invoked when an object is created whereas method has to be called explicitly.
What are methods and how are they defined? - Answers Methods are functions that operate on
instances of classes in which they are defined. Objects can communicate with each other using methods
and can call methods in other classes. Method definition has four parts. They are name of the method,
type of object or primitive type the method returns, a list of parameters and the body of the method. A
method's signature is a combination of the first three parts mentioned above.
What is the use of bin and lib in JDK? - Answers Bin contains all tools such as javac, appletviewer, awt
tool, etc., whereas lib contains API and all packages.
What is casting? - Answers Casting is used to convert the value of one type to another.
How many ways can an argument be passed to a subroutine and explain them? - Answers An argument
can be passed in two ways. They are passing by value and passing by reference. Passing by value: This
method copies the value of an argument into the formal parameter of the subroutine. Passing by
reference: In this method, a reference to an argument (not the value of the argument) is passed to the
parameter.
, What is the difference between an argument and a parameter? - Answers While defining method,
variables passed in the method are called parameters. While using those methods, values passed to
those variables are called arguments.
What are different types of access modifiers? - Answers public: Any thing declared as public can be
accessed from anywhere. private: Any thing declared as private can't be seen outside of its class.
protected: Any thing declared as protected can be accessed by classes in the same package and
subclasses in the other packages. default modifier : Can be accessed only to classes in the same package.
What is final, finalize() and finally? - Answers final : final keyword can be used for class, method and
variables. A final class cannot be subclassed and it prevents other programmers from subclassing a
secure class to invoke insecure methods. A final method can't be overridden. A final variable can't
change from its initialized value. finalize() : finalize() method is used just before an object is destroyed
and can be called just prior to garbage collection. finally : finally, a key word used in exception handling,
creates a block of code that will be executed after a try/catch block has completed and before the code
following the try/catch block. The finally block will execute whether or not an exception is thrown. For
example, if a method opens a file upon exit, then you will not want the code that closes the file to be
bypassed by the exception-handling mechanism. This finally keyword is designed to address this
contingency.
What is UNICODE? - Answers Unicode is used for internal representation of characters and strings and it
uses 16 bits to represent each other.
What is Garbage Collection and how to call it explicitly? - Answers When an object is no longer referred
to by any variable, java automatically reclaims memory used by that object. This is known as garbage
collection. System. gc() method may be used to call it explicitly.
What is finalize() method? - Answers finalize () method is used just before an object is destroyed and can
be called just prior to garbage collection.
What are Transient and Volatile Modifiers? - Answers Transient: The transient modifier applies to
variables only and it is not stored as part of its object's Persistent state. Transient variables are not
serialized. Volatile: Volatile modifier applies to variables only and it tells the compiler that the variable
modified by volatile can be changed unexpectedly by other parts of the program.
What is method overloading and method overriding? - Answers Method overloading: When a method in
a class having the same method name with different arguments is said to be method overloading.
Method overriding : When a method in a class having the same method name with same arguments is
said to be method overriding.
What is difference between overloading and overriding? - Answers a) In overloading, there is a
relationship between methods available in the same class whereas in overriding, there is relationship
between a superclass method and subclass method. b) Overloading does not block inheritance from the
superclass whereas overriding blocks inheritance from the superclass. c) In overloading, separate
