String s1 = "Java"; String s2 = s1; s1 = s1.toUpperCase(); System.out.println(s1 + " " + s2);

int x = -5; if(x < 0) if(x % 2 == 0) System.out.println("Even Negative"); else System.out.println("Odd Negative"); else System.out.println("Positive");

int n = 1; switch(n){ case 1: System.out.print("A "); case 2: System.out.print("B "); default: System.out.print("C"); }

int[] arr = {1, 2, 3, 4};

for(int x : arr) {

x *= 2;

}

for(int i = 0; i < arr.length; i++) {

arr[i] += 3;

}

System.out.println(Arrays.toString(arr));

ArrayList list = new ArrayList<>(); list.add("A"); list.add("B"); list.add(1, "C"); System.out.println(list);

Set set = new HashSet<>(); set.add(5); set.add(3); set.add(5); set.add(2); System.out.println(set.contains(5) + " " + set.size());

Map map = new HashMap<>(); map.put("X", 10); map.put("Y", 20); map.put("X", 30); map.put("X", 30); System.out.println(map.get("X") + " " + map.size());

class A { void msg(){ System.out.println("A"); } } class B extends A { void msg(){ System.out.println("B"); } } class C extends B { } C obj = new C(); obj.msg();

class Test { void show(int a){ System.out.println("int"); } void show(double a){ System.out.println("double"); } } new Test().show(5);

Recursion Output static int sum(int n){ if(n==0) return 0; return n + sum(n-1); } System.out.println(sum(3));

What will be the output if the following code is executed? class A { void msg(){ System.out.println("A"); } } class B extends A { void msg(){ System.out.println("B"); } } A obj = new B(); obj.msg();

ArrayList list = new ArrayList<>(Arrays.asList(1,2,3)); list.remove(1); System.out.println(list);

int[] arr = {1,2,3};

for(int i=0;i<arr.length/2;i++){

int temp = arr[i];

arr[i]=arr[arr.length-1-i];

arr[arr.length-1-i]=temp;

}

System.out.println(Arrays.toString(arr));

class A {void msg() { System.out.println("A"); }}
class B extends A {void msg() { System.out.println("B"); }}

List list = new ArrayList<>();
list.add(new B());
list.add(new A());
for(A obj : list) obj.msg();

Match the OOP concepts with the correct description:

1. Encapsulation

2. Inheritance

3. Polymorphism

4. Abstraction

Descriptions:

• (i) Hiding internal details and exposing essential features

• (ii) Wrapping data + methods together

• (iii) Using one interface to represent multiple forms

• (iv) Acquiring properties of another class

Correct Mapping:

Which statement about abstraction is correct?
a) Abstraction is achieved using abstract classes and interfaces
b) Abstraction is hiding data inside a class using private variables
c) Abstraction is achieved only through constructors
d) Abstraction means method overloading

Why is String in Java considered immutable?
a) Because it is declared as final
b) Because changing a string creates a new object in the heap
c) Because it is a primitive type
d) Because it cannot be stored in heap memory

Which of the following is correct?
a) Encapsulation = hiding internal details, Abstraction = binding data & methods
b) Abstraction = hiding implementation, Encapsulation = restricting direct access
c) Both are exactly the same concept
d) Encapsulation can only be achieved using interfaces

class Test {

void show(int a, long b) { System.out.println("int-long"); }

void show(long a, int b) { System.out.println("long-int"); }

}

public class Main {

public static void main(String[] args) {

new Test().show(10, 10);

}

}