Nagpur University Previous Year Question Paper Summer 2023

B.Tech (Fifth Semester) CBCS Summer 2023. (Information Technology)

Subject: Java Programming

Questions:

1. Explain method overloading with example in java.
2. Explain the following operators used in Java Programming
   i) Arithmetic Operators
   ii) Bitwise Operators
   iii) Relational Operators
   iv) Logical Operators
3. What is constructor? Explain the different types of constructor with example.
4. With suitable Java program segment explain the keywords static & final.
5. What is vector class in java? Write a program to demonstrate some of the methods associated with vector class.
6. Define package. What are the types of Package? How to create and access the package?
7. What is the significance of wrapper classes in java programs? Explain any one java wrapper class with suitable ova code.
8. What is exception Handling in Java? Write a program to handle arithmetic exception.
9. Write the two ways of creating threads in Java programming. Explain the methods isAlive() and join() and trace the output, when we use these methods in Java program.
10. What do you mean by synchronization among the threads. Write a java program using synchronized keyword.
11. What do you mean by multitasking and multithreading? Draw neatly the life cycle of a thread, explain with suitable Java program.
12. Explain the following. i) Multithreading Applications in real life. ii) Sleep ( ) and suspend method.
13. Write a java program which reads a string and then check whether the entered string is palindrome or not.
14. Explain the methods of string class i) valueOf ii) toString
15. Write a java Program in java, Calender class display the current date and display Date after 15 days, 4 month, 2 year later from current date.
16. What is hashCode() method in Java? What is use of hashCode() method in Java” Write Java program to demonstrate working of hashCode() and toString().
17. What is HashSet class? Write a program in Java to display elements in Hashset.
18. What is Iterator Interface? Explain method defined in Iterator Interface.
19. What is the collection interface? Explain method defined in collection interface.
20. Write a program in Java to use of binary search method by using search algorithms in the collection Framework.

1. Method Overloading in Java

Method Overloading is compile-time polymorphism where multiple methods share the same name but differ in parameters (number, type, or order). It allows flexible method calls.

Example:

class OverloadDemo {
    void display() { System.out.println("No args"); }
    void display(int a) { System.out.println("Int: " + a); }
    void display(String s) { System.out.println("String: " + s); }
}

public class Main {
    public static void main(String[] args) {
        OverloadDemo obj = new OverloadDemo();
        obj.display(); // No args
        obj.display(10); // Int: 10
        obj.display("Hello"); // String: Hello
    }
}

Output:

No args
Int: 10
String: Hello

2. Operators in Java

i) Arithmetic Operators: Perform mathematical operations.

• + (addition), - (subtraction), * (multiplication), / (division), % (modulus).
  Example: int a = 10 + 5; // 15

ii) Bitwise Operators: Operate on bits.

• & (AND), | (OR), ^ (XOR), ~ (NOT), << (left shift), >> (right shift), >>> (unsigned right shift).
  Example: int b = 5 & 3; // 1

iii) Relational Operators: Compare values, return boolean.

• == (equal), != (not equal), > (greater), < (less), >=, <=.
  Example: boolean c = 10 > 5; // true

iv) Logical Operators: Combine boolean expressions.

• && (AND), || (OR), ! (NOT).
  Example: boolean d = (true && false); // false

3. Constructor in Java

A constructor is a special method called when an object is created to initialize it. Same name as class, no return type.

Types:

• Default: No parameters, provided if none defined.
  Example: class Test { Test() { System.out.println("Default"); } }
• Parameterized: Accepts parameters.
  Example: class Test { Test(int a) { System.out.println("Param: " + a); } }
• Copy: Copies one object’s state to another.
  Example: class Test { int x; Test(Test t) { x = t.x; } }

Full Example:

class Box {
    int width;
    Box() { width = 10; } // Default
    Box(int w) { width = w; } // Parameterized
    Box(Box b) { width = b.width; } // Copy
}

public class ConstructorDemo {
    public static void main(String[] args) {
        Box b1 = new Box(); // Default
        Box b2 = new Box(20); // Parameterized
        Box b3 = new Box(b2); // Copy
        System.out.println("Widths: " + b1.width + ", " + b2.width + ", " + b3.width);
    }
}

Output: Widths: 10, 20, 20

4. static & final Keywords

static: Belongs to class, not instances. Shared across objects, loaded once.
final: Constant; cannot be modified (variables), overridden (methods), or extended (classes).

Example:

class Demo {
    static int count = 0; // Static variable
    final int MAX = 100; // Final variable

    static void increment() { // Static method
        count++;
    }

    final void show() { // Final method
        System.out.println("MAX: " + MAX + ", Count: " + count);
    }
}

public class KeywordDemo {
    public static void main(String[] args) {
        Demo.increment(); // Static call
        Demo obj = new Demo();
        obj.show(); // Final method
    }
}

Output: MAX: 100, Count: 1

5. Vector Class in Java

Vector is a dynamic array (java.util.Vector) that grows automatically, synchronized for thread-safety. Methods: add(), get(), remove(), size(), etc.

Program:

import java.util.Vector;

public class VectorDemo {
    public static void main(String[] args) {
        Vector<Integer> v = new Vector<>();
        v.add(10); // add()
        v.add(20);
        System.out.println("Size: " + v.size()); // size()
        System.out.println("Element at 0: " + v.get(0)); // get()
        v.remove(0); // remove()
        System.out.println("Updated: " + v);
    }
}

Output:

Size: 2
Element at 0: 10
Updated: [20]

6. Package in Java

A package is a namespace for organizing classes/interfaces. Prevents naming conflicts.

Types:

• Built-in: Java-provided (e.g., java.util).
• User-defined: Custom (e.g., mypack).

Create: Use package mypack; at file top. Compile with -d ..

Access: Use import mypack.*; or fully qualified name.

Example: See question 7 from previous set for code.

7. Wrapper Classes in Java

Wrapper Classes convert primitives to objects (e.g., int to Integer). Significance: Use in collections, generics; provide utility methods.

Example: Integer Wrapper:

public class WrapperDemo {
    public static void main(String[] args) {
        int primitive = 10;
        Integer wrapper = Integer.valueOf(primitive); // Wrap
        System.out.println("Value: " + wrapper.intValue()); // Unwrap
        System.out.println("Parse: " + Integer.parseInt("20")); // Utility
    }
}

Output:

Value: 10
Parse: 20

8. Exception Handling in Java

Exception Handling manages runtime errors using try-catch-finally. Prevents abrupt termination.

Program for ArithmeticException:

public class ArithmeticExceptionDemo {
    public static void main(String[] args) {
        try {
            int result = 10 / 0; // Throws ArithmeticException
        } catch (ArithmeticException e) {
            System.out.println("Error: " + e.getMessage());
        } finally {
            System.out.println("Cleanup");
        }
    }
}

Output:

Error: / by zero
Cleanup

9. Creating Threads in Java

Ways:

1. Extend Thread class, override run().
2. Implement Runnable interface, pass to Thread.

isAlive(): Checks if thread is alive.
join(): Waits for thread to finish.

Program:

class MyThread extends Thread {
    public void run() { System.out.println("Thread running"); }
}

public class ThreadCreateDemo {
    public static void main(String[] args) throws InterruptedException {
        MyThread t = new MyThread();
        System.out.println("Alive before start: " + t.isAlive()); // false
        t.start();
        System.out.println("Alive after start: " + t.isAlive()); // true
        t.join(); // Wait
        System.out.println("Alive after join: " + t.isAlive()); // false
    }
}

Output:

Alive before start: false
Alive after start: true
Thread running
Alive after join: false

10. Synchronization in Threads

Synchronization ensures only one thread accesses shared resources at a time, preventing data inconsistency. Use synchronized keyword.

Program:

class Counter {
    int count = 0;
    synchronized void increment() { count++; }
}

public class SyncDemo {
    public static void main(String[] args) throws InterruptedException {
        Counter c = new Counter();
        Thread t1 = new Thread(() -> { for (int i = 0; i < 1000; i++) c.increment(); });
        Thread t2 = new Thread(() -> { for (int i = 0; i < 1000; i++) c.increment(); });
        t1.start(); t2.start();
        t1.join(); t2.join();
        System.out.println("Count: " + c.count); // 2000 (consistent)
    }
}

Output: Count: 2000

11. Multitasking vs Multithreading

Multitasking: OS runs multiple processes concurrently.
Multithreading: Single process runs multiple threads concurrently, sharing resources.

Thread Lifecycle: New → Runnable → Running → Blocked/Waiting → Terminated.

Program (Multithreading):

class MultiThread implements Runnable {
    public void run() { System.out.println("Thread: " + Thread.currentThread().getName()); }
}

public class MultiDemo {
    public static void main(String[] args) {
        Thread t1 = new Thread(new MultiThread(), "T1");
        Thread t2 = new Thread(new MultiThread(), "T2");
        t1.start(); t2.start();
    }
}

Output (varies):

Thread: T1
Thread: T2

12. Multithreading Applications, sleep() and suspend()

i) Multithreading Applications: Real-life: Web servers (handle multiple requests), games (AI, rendering), media players (playback, UI).

ii) sleep(): Pauses thread for milliseconds (static, throws InterruptedException).
suspend(): Deprecated; pauses thread (unsafe, can cause deadlocks).

Example: Thread.sleep(1000); // Pause 1s

13. Palindrome String Program

import java.util.Scanner;

public class Palindrome {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter string: ");
        String s = sc.nextLine();
        String rev = new StringBuilder(s).reverse().toString();
        if (s.equals(rev)) {
            System.out.println("Palindrome");
        } else {
            System.out.println("Not Palindrome");
        }
    }
}

Sample Output (input: “radar”): Palindrome

14. String Methods: valueOf() and toString()

valueOf(): Converts primitives/objects to String (static).
toString(): Returns string representation of object.

See question 15 from previous set for code example.

15. Calendar Class Program

import java.util.Calendar;

public class CalendarDemo {
    public static void main(String[] args) {
        Calendar cal = Calendar.getInstance();
        cal.set(2025, Calendar.SEPTEMBER, 20); // Current: Sep 20, 2025

        System.out.println("Current: " + cal.getTime());

        cal.add(Calendar.DAY_OF_MONTH, 15); // +15 days
        System.out.println("+15 days: " + cal.getTime());

        cal.set(2025, Calendar.SEPTEMBER, 20); // Reset
        cal.add(Calendar.MONTH, 4); // +4 months
        System.out.println("+4 months: " + cal.getTime());

        cal.set(2025, Calendar.SEPTEMBER, 20); // Reset
        cal.add(Calendar.YEAR, 2); // +2 years
        System.out.println("+2 years: " + cal.getTime());
    }
}

Output (approximate format):

Current: Sat Sep 20 00:00:00 IST 2025
+15 days: Sun Oct 05 00:00:00 IST 2025
+4 months: Tue Jan 20 00:00:00 IST 2026
+2 years: Mon Sep 20 00:00:00 IST 2027

16. hashCode() in Java

hashCode(): Returns integer hash code for object, used in hashing (e.g., HashMap). Equals objects must have same hashCode.

Program:

class Person {
    String name;
    Person(String name) { this.name = name; }

    @Override
    public int hashCode() { return name.hashCode(); }

    @Override
    public String toString() { return "Person: " + name; }
}

public class HashDemo {
    public static void main(String[] args) {
        Person p = new Person("Alice");
        System.out.println("hashCode: " + p.hashCode());
        System.out.println("toString: " + p.toString());
    }
}

Output (varies):

hashCode: 63405538
toString: Person: Alice

17. HashSet Class in Java

HashSet is a collection (java.util.HashSet) storing unique elements, no order, based on hash table.

Program:

import java.util.HashSet;

public class HashSetDemo {
    public static void main(String[] args) {
        HashSet<String> set = new HashSet<>();
        set.add("Apple");
        set.add("Banana");
        set.add("Apple"); // Duplicate ignored
        System.out.println("Elements: " + set);
    }
}

Output (order varies): Elements: [Apple, Banana]

18. Iterator Interface

Iterator (java.util.Iterator) traverses collections. Methods:

• hasNext(): Returns true if more elements.
• next(): Returns next element.
• remove(): Removes last returned element (optional).

Example: Iterator<String> it = list.iterator(); while (it.hasNext()) { System.out.println(it.next()); }

19. Collection Interface

Collection (java.util.Collection) is root interface for collections. Methods:

• add(E e): Adds element.
• remove(Object o): Removes element.
• size(): Returns size.
• iterator(): Returns iterator.
• contains(Object o): Checks presence.

20. Binary Search in Collections

import java.util.ArrayList;
import java.util.Collections;

public class BinarySearchDemo {
    public static void main(String[] args) {
        ArrayList<Integer> list = new ArrayList<>();
        list.add(5); list.add(1); list.add(3);
        Collections.sort(list); // Must sort first
        int index = Collections.binarySearch(list, 3);
        System.out.println("Index of 3: " + index); // 2
    }
}

Output: Index of 3: 2