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GNDU Queson Paper - 2021
Bachelor of Computer Applicaon (BCA) 5st Semester
JAVA PROGRAMMING LANGUAGE
Paper-IV
Time Allowed – 3 Hours Maximum Marks-75
Note :- Aempt FIVE Queson in all, selecng at least ONE queson from each secon . The FIFTH
Queson may be aempted from any Secon . All Quesons carry equal marks .
SECTION-A
1.Which are various data types of Java ? what is dierence between keyword, idener, literal and
operator ? Give example of each.
2.(a) Explain Object Oriented features of Java.
(b) What is dierence between class and object ? Give example.
SECTION-B
3.What is use of method overriding and method overloading ? Give an example of both. What is
use of super and nal keywords ?
4.What is Interface ? What are various similaries and dierences between class and Interface?
SECTION-C
5. Explain the use of the following in Java :
(a) try-catch
(b) try-nally
(c) throw and throws
6. What is use of threads ? Explain the thread life cycle.
SECTION-D
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7. Explain the following :
(a) Buered Input / Output stream
(b) JDBC
8. Write a program in java to show records of employee table of My SQL . Assume table as :
Employee (EmpID, EmpName, Salery, DOJ)
Gndu Answer Paper 2021
Bachelor of Computer Applicaon (BCA) 5st Semester
JAVA PROGRAMMING LANGUAGE
Paper-IV
SECTION-A
1.Which are various data types of Java ? what is dierence between keyword, idener,
literal and operator ? Give example of each.
Ans: In Java, there are several data types that help dene and categorize the type of data a
variable can hold. Let's explore these data types and clarify the dierences between
keywords, ideners, literals, and operators:
**Data Types in Java:**
1. **Primive Data Types:**
- These are the basic data types in Java that represent simple values.
- Examples:
- `int`: Used for whole numbers, e.g., `int age = 30;`
- `double`: Used for oang-point numbers, e.g., `double price = 19.99;`
- `boolean`: Used for true or false values, e.g., `boolean isReady = true;`
- `char`: Used for single characters, e.g., `char grade = 'A';`
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2. **Reference Data Types:**
- These data types are more complex and store references to objects.
- Examples:
- `String`: Used for storing text, e.g., `String name = "John";`
- `Object`: The most generic type that can refer to any object, e.g., `Object person = new
Person();`
**Dierences:**
1. **Keyword**:
- Keywords are reserved words in Java that have specic meanings and purposes.
- They cannot be used as ideners (variable names).
- Example: `public`, `class`, `if`, `return`.
2. **Idener**:
- Ideners are names used for variables, methods, classes, and other user-dened
elements.
- They should start with a leer, underscore, or dollar sign, followed by leers, numbers,
underscores, or dollar signs.
- Example: `myVariable`, `calculateTotal`, `MyClass`.
3. **Literal**:
- Literals represent constant values in Java.
- They can be of dierent types, such as numeric literals (`10`, `3.14`), character literals
(`'A'`, `'1'`), string literals (`"Hello"`), and boolean literals (`true`, `false`).
4. **Operator**:
- Operators are symbols used to perform operaons on data.
- They can be arithmec operators (`+`, `-`, `*`), comparison operators (`>`, `<`, `==`), logical
operators (`&&`, `||`), and more.
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- Example: `x + y`, `age > 18`, `isReady && isAcve`.
In summary, Java provides a variety of data types to work with dierent types of data.
Keywords are reserved words with specic meanings, ideners are names for user-dened
elements, literals represent constant values, and operators are symbols used for various
operaons. Understanding the disncons between these concepts is essenal for eecve
Java programming.
2.(a) Explain Object Oriented features of Java
Ans: Certainly! Java is an object-oriented programming language, which means it's designed
to work with objects, allowing you to structure your code in a way that's more organized and
easier to manage. Here, I'll explain some key object-oriented features of Java with examples:
1. **Classes and Objects**:
- **Explanaon**: In Java, everything is based on classes and objects. A class is like a
blueprint, and an object is an instance of that blueprint.
- **Example**:
2. **Encapsulaon**:
- **Explanaon**: Encapsulaon is about bundling data (aributes) and methods
(funcons) that operate on the data into a single unit (class). This helps in data hiding and
access control.
- **Example**:
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3. **Inheritance**:
- **Explanaon**: Inheritance allows a new class (subclass or child class) to inherit
properes and behaviors from an exisng class (superclass or parent class).
- **Example**:
4. **Polymorphism**:
- **Explanaon**: Polymorphism allows objects of dierent classes to be treated as
objects of a common superclass. It enables method overriding and dynamic method
invocaon.
- **Example**:
5. **Abstracon**:
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- **Explanaon**: Abstracon is the process of simplifying complex reality by modeling
classes based on what an object does rather than how it does it.
- **Example**:
In summary, Java's object-oriented features help developers build modular, maintainable,
and reusable code. Classes and objects are the building blocks, encapsulaon ensures data
security, inheritance promotes code reuse, polymorphism enables exibility, and abstracon
simplies complex systems. These concepts make Java a powerful and widely used
programming language.
(b) What is dierence between class and object ? Give example.
Ans: Certainly! Let's explore the dierence between a class and an object .
**Class**:
A class is like a blueprint or a template for creang objects. It denes the characteriscs and
behaviors that objects of a parcular type will have. Think of a class as a set of instrucons
for building something. It doesn't exist in the real world but serves as a plan for creang
objects.
**Object**:
An object, on the other hand, is a specic instance created from a class. It's like the actual
thing built using the blueprint. Objects have their own unique properes and can perform
acons dened in the class. You can have mulple objects created from the same class, each
with its own disnct aributes and behavior.
**Example**:
Let's use a simple analogy to illustrate the dierence. Imagine you have a class called "Car."
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- **Class (Car Blueprint)**: The "Car" class denes what a car is. It species that a car has
properes like color, make, and model, and it can perform acons like starng, stopping, and
honking. But the class itself doesn't represent any specic car; it's just a descripon of what
a car should be.
- **Objects (Actual Cars)**: Objects are instances of the "Car" class. You can create real cars
from the blueprint. For instance, you might create two objects: one represenng a red Ford
Mustang and another represenng a blue Toyota Camry. Each of these objects will have its
own color, make, model, and can be driven independently.
In summary, a class is the plan or blueprint, and an object is the real thing created based on
that plan. Classes allow us to dene the structure and behavior of objects, making it easier
to create and manage dierent instances of the same type.
SECTION-B
3.What is use of method overriding and method overloading ? Give an example of both.
What is use of super and nal keywords ?
Ans: **Method Overloading** and **Method Overriding** are two fundamental concepts
in object-oriented programming, oen used in languages like Java or C++.
**Method Overloading**:
Method overloading is when you have mulple methods in the same class with the same
name but dierent parameters. It's used to create methods that perform similar tasks but
can handle dierent types of input. This way, you don't need to create a dierent method for
each case. Here's an example:
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In this example, we have two `add` methods with dierent parameter types (int and double).
This allows you to add both integers and oang-point numbers using the same method
name.
**Method Overriding**:
Method overriding is used when you have a method in a parent class, and you want to
provide a specic implementaon of that method in a child class. It's a way to change or
extend the behavior of the inherited method. For instance:
Here, the `draw` method in the `Shape` class is overridden in the `Circle` class to provide a
specialized implementaon for drawing a circle.
**super Keyword**:
The `super` keyword is used to call a method or access a variable from the parent class. It's
handy when you're overriding a method in a child class but sll want to use the funconality
of the parent class. For example:
**nal Keyword**:
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The `nal` keyword is used to prevent further modicaon of a class, method, or variable.
When a class is declared as `nal`, it cannot be extended (no inheritance). When a method is
marked as `nal`, it can't be overridden by child classes. For example:
In summary, method overloading and overriding allow you to create exible and specialized
code, while the `super` keyword lets you access parent class elements in child classes, and
the `nal` keyword restricts further modicaons to classes or methods.
4.What is Interface ? What are various similaries and dierences between class and
Interface?
Ans: An interface is a concept in programming that denes a contract for how classes should
behave. It sets up a list of methods that must be implemented by any class that claims to
conform to the interface. In simpler terms, an interface is like a blueprint for classes, telling
them what methods they need to have and how they should work. Here's an easy-to-
understand explanaon of the similaries and dierences between classes and interfaces:
**Similaries**:
1. **Methods**: Both classes and interfaces can have methods. A method is a block of code
that performs a specic task. Classes can have their methods, and interfaces can declare
methods that classes must implement.
2. **Polymorphism**: Both classes and interfaces contribute to polymorphism, a
fundamental concept in object-oriented programming. Polymorphism allows objects of
dierent classes to be treated as objects of a common interface. This means you can use
objects in a generic way, making your code more exible and adaptable.
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**Dierences**:
1. **Implementaon**: The most signicant dierence is that classes can contain both
method declaraons and method implementaons. In contrast, an interface can only declare
method signatures (names, parameters, and return types) but can't provide the actual code
for those methods.
2. **Inheritance**: Classes can extend (inherit from) other classes, inhering their
properes and methods. However, a class can only inherit from one class (single
inheritance). In contrast, a class can implement mulple interfaces. This allows a class to
promise that it will provide the behavior specied in mulple interfaces.
3. **Constructor**: Classes have constructors, which are special methods used to create
and inialize objects. Interfaces can't have constructors because they don't create objects
themselves; they dene a set of rules for how objects should behave.
4. **Variables**: Classes can have instance variables (also called elds or properes) that
store data. Interfaces can't have instance variables; they dene the structure and behavior
but don't store data.
In summary, a class is like a blueprint for creang objects, and it can provide the actual
implementaon of methods. An interface, on the other hand, is like a contract that classes
promise to follow, specifying what methods they should have without providing the method
implementaons. While classes enable code reusability through inheritance, interfaces allow
classes to support mulple contracts, enabling greater exibility in designing and structuring
your code.
SECTION-C
5. Explain the use of the following in Java :
(a) try-catch
(b) try-nally
(c) throw and throws
Ans: (a) **try-catch**:
- In Java, `try` and `catch` are used together to handle excepons. When you put a block of
code inside a `try` block, you're telling Java to monitor for errors within that code. If an error
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occurs, it's caught by the `catch` block, prevenng your program from crashing. This is
essenal for robust programming because it allows you to gracefully handle unexpected
issues. For instance, if you're reading a le and it doesn't exist, you can catch the
"FileNotFound" excepon and display a user-friendly error message instead of leng the
program crash. In easy terms, think of "try-catch" as a safety net for your code.
(b) **try-nally**:
- The `try-nally` block is used to ensure that a specic piece of code (usually clean-up or
resource release code) is always executed, whether an excepon is thrown or not. For
instance, if you open a le or a database connecon inside a `try` block, you can use `try-
nally` to guarantee that the le is closed or the database connecon is properly
terminated, even if an excepon occurs. It's like making sure you turn o the lights and lock
the door when leaving a room, regardless of what happens while you're in there.
(c) **throw and throws**:
- In Java, `throw` is used to explicitly create and throw an excepon when a parcular
condion is met. This is useful when you want to signal that something unexpected has
happened in your code. For example, you might `throw` a custom excepon if a user tries to
log in with an incorrect password. On the other hand, `throws` is used in a method signature
to indicate that the method might throw an excepon. It doesn't handle the excepon; it
simply informs the calling code that it should be prepared to catch an excepon that might
be thrown by the method. It's like pung a "Cauon: Wet Floor" sign, warning others about
a potenal hazard.
In summary, these constructs in Java help you deal with unexpected situaons, ensure
proper resource management, and communicate the possibility of excepons to other parts
of your code. They are crucial for wring reliable and robust Java programs.
6. What is use of threads ? Explain the thread life cycle.
Ans: **Threads** are a crucial part of computer programs that help them run smoothly and
eciently. Think of them as lile workers inside your computer, each handling a specic
task.
**Thread Life Cycle**:
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1. **New**: A thread begins its life in the "New" state. It's like a new employee who's just
been hired. In this stage, the thread is created but hasn't started running yet.
2. **Runnable**: When the thread is ready to work, it moves to the "Runnable" state. Just
like a worker waing for their turn, a runnable thread is in the queue to be executed.
3. **Running**: The thread enters the "Running" state when it's acvely execung its tasks.
Imagine this as the worker doing their job. In a mul-core processor, mulple threads can be
in the running state simultaneously.
4. **Blocked/Waing**: Somemes, a thread can't connue its work, like when it's waing
for some data or a resource. In this state, it's "Blocked" or "Waing" for the necessary
condions to proceed.
5. **Terminated**: When a thread completes its task or is no longer needed, it enters the
"Terminated" state. This is like an employee who nishes their work and leaves the company.
6. **Dead**: Once a thread is terminated, it's considered "Dead." It can't be restarted or
moved to another state. It's like a former employee who's no longer part of the company.
Threads are incredibly useful in programming because they allow mulple tasks to be
executed concurrently. This means your computer can do several things at once, like playing
music while browsing the internet or running background tasks while you're using an
applicaon. However, managing threads can be complex, and programmers need to ensure
they work together without causing problems, like data conicts or crashes. So, threads are
like the workforce of your computer, making sure everything runs eciently and smoothly.
SECTION-D
7. Explain the following :
(a) Buered Input / Output stream
Ans: Buered Input/Output Stream
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Buered Input and Output streams are concepts in computer programming that help
improve the eciency of reading and wring data to and from les or other sources like
network connecons. Imagine you are pouring water from a large container into smaller
cups. You can either pour one drop at a me (unbuered), or you can pour a bit into a
smaller container and then pour from that smaller container into the cups (buered).
Buered streams work somewhat like that smaller container, making the process more
ecient.
**Buered Input Stream**:
When you read data from a le or some other source, it's oen done in small pieces. Each
me you read a piece, your program may need to interact with the le system or network,
which can be slow. Buered Input Streams, however, read data in larger chunks and store it
in a temporary memory space (the buer) before your program uses it. This reduces the
number of interacons with the le system or network, making the reading process faster.
It's like collecng a bunch of puzzle pieces before assembling them, rather than geng one
piece at a me.
**Buered Output Stream**:
Similarly, when you write data to a le or send it over a network, each small piece may
trigger a separate interacon with the output desnaon, which can also be slow. Buered
Output Streams collect a poron of your data in the buer and then write it all at once,
reducing the number of interacons and making wring more ecient. It's like pouring
mulple cups of water from your smaller container in one go, rather than one cup at a me.
In essence, buered streams act as intermediaries that help reduce the me your program
spends interacng with the le system or network, which speeds up the process of reading
and wring data. They are a fundamental part of opmizing le I/O operaons in soware
development.
(b) JDBC
Ans: JDBC, which stands for Java Database Connecvity, is a technology that allows Java
programs to interact with databases. It's like a bridge between the world of Java and the
world of databases, making it easy for Java applicaons to retrieve, store, and manipulate
data in a database.
Here's a simple breakdown of what JDBC does and why it's important:
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1. **Database Interacon**: JDBC enables Java applicaons to connect to a wide range of
databases, such as MySQL, Oracle, or PostgreSQL. It acts as a communicator that
understands the language of both Java and the specic database system.
2. **Database Access**: Once connected, Java applicaons can send SQL (Structured Query
Language) statements to the database using JDBC. SQL statements are like commands that
tell the database what to do, such as retrieving specic data or updang records.
3. **Data Retrieval**: With JDBC, you can fetch data from a database and use it in your Java
program. For example, if you have an e-commerce applicaon, you can use JDBC to retrieve
product informaon, like names, prices, and descripons from the database and display
them on your website.
4. **Data Modicaon**: JDBC also allows you to insert, update, and delete data in the
database. If a customer places an order, JDBC can be used to store this informaon in the
database for future reference.
5. **Security**: JDBC provides features for secure database interacons. You can control
who can access the database and what they can do, ensuring that sensive data is
protected.
6. **Portability**: JDBC is plaorm-independent, which means you can write your Java
applicaon with JDBC, and it will work with dierent databases without major modicaons.
This makes it versale and saves me when switching databases or plaorms.
In essence, JDBC is a crical tool for developers because it simplies the process of
integrang databases with Java applicaons. It empowers soware to store, retrieve, and
manage data, making it essenal for any applicaon that needs to work with data stored in a
database system.
8.Write a program in java to show records of employee table of My SQL . Assume table as :
Employee (EmpID, EmpName, Salery, DOJ)
Ans: Certainly! To show records from an Employee table in a MySQL database using Java,
you can follow these easy-to-understand steps. First, ensure you have the MySQL
Connector/J library in your Java project to interact with the database.
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Remember to replace `yourDatabaseName`, `yourUsername`, and `yourPassword` with your
actual database details. This Java program connects to the MySQL database, retrieves
records from the Employee table, and prints them to the console. It uses JDBC (Java
Database Connecvity) to establish the connecon and execute the SQL query.
Please ensure that you have the MySQL Connector/J library included in your project, and the
MySQL server is up and running. Also, handle excepons and close the connecons properly
for robust code.
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