Online Quiz Attempt – Play & Test Your Knowledge

Question 1

1 / 10

Given the following code snippet: `class A { public void methodA() throws Exception { System.out.println("A"); } } class B extends A { public void methodA() { System.out.println("B"); } } public class Main { public static void main(String[] args) { A a = new B(); try { a.methodA(); } catch (Exception e) { System.out.println("Exception"); } } }`. What will be the output?

A

B

C

Exception

D

Compiler Error

Question 2

2 / 10

Which of the following statements is true regarding the Java Memory Model (JMM)?

A

The JMM guarantees that all threads have a consistent view of memory at all times.

B

The JMM defines a total order of all memory operations.

C

The JMM allows for compiler and processor optimizations that may reorder memory operations as long as the program's semantics are preserved.

D

The JMM is not applicable to multi-core processors.

Question 3

3 / 10

Consider the following code snippet: `Integer i1 = 100; Integer i2 = 100; Integer i3 = 200; Integer i4 = 200; System.out.println(i1 == i2); System.out.println(i3 == i4);`. What will be the output?

A

true true

B

true false

C

false true

D

false false

Question 4

4 / 10

Which of the following is the most accurate description of the difference between `HashMap` and `ConcurrentHashMap`?

A

`HashMap` is thread-safe, while `ConcurrentHashMap` is not.

B

`ConcurrentHashMap` provides better performance than `HashMap` in single-threaded environments.

C

`ConcurrentHashMap` provides thread-safety using lock striping, allowing multiple threads to access different parts of the map concurrently, while `HashMap` is not thread-safe.

D

`HashMap` allows null keys and values, while `ConcurrentHashMap` does not.

Question 5

5 / 10

What is the primary purpose of the `volatile` keyword in Java?

A

To ensure that a variable is stored in the CPU cache.

B

To prevent the compiler from optimizing away a variable that is not actively used.

C

To guarantee atomicity of compound operations on a variable.

D

To ensure that all threads see the most up-to-date value of a variable, forcing the read from main memory instead of CPU cache, and prevent instruction reordering that can lead to unexpected results in multithreaded environments.

Question 6

6 / 10

Which of the following statements correctly describes the difference between Checked and Unchecked Exceptions in Java?

A

Checked exceptions are subclasses of `RuntimeException`, while unchecked exceptions are subclasses of `Exception`.

B

Checked exceptions must be caught or declared to be thrown, while unchecked exceptions do not.

C

Unchecked exceptions are handled at compile time, while checked exceptions are handled at runtime.

D

There is no difference between checked and unchecked exceptions.

Question 7

7 / 10

What is the output of the following code snippet: `String s1 = "abc"; String s2 = new String("abc"); System.out.println(s1 == s2); System.out.println(s1.equals(s2));`?

A

true true

B

true false

C

false true

D

false false

Question 8

8 / 10

Which of the following is the correct way to implement a thread-safe counter using `AtomicInteger` in Java?

A

`int count = 0; public synchronized void increment() { count++; }`

B

`AtomicInteger count = new AtomicInteger(0); public void increment() { count.incrementAndGet(); }`

C

`AtomicInteger count = new AtomicInteger(0); public synchronized void increment() { count.getAndIncrement(); }`

D

`int count = 0; public void increment() { count++; }`

Question 9

9 / 10

What is the purpose of the `transient` keyword in Java?

A

To make a variable thread-safe.

B

To prevent a variable from being serialized.

C

To make a variable accessible from any class.

D

To force a variable to be stored in main memory.

Question 10

10 / 10

Given the following code: `interface I1 { default void method() { System.out.println("I1"); } } interface I2 { default void method() { System.out.println("I2"); } } class MyClass implements I1, I2 { public void method() { I1.super.method(); } } public class Main { public static void main(String[] args) { new MyClass().method(); } }`. What will be printed?

A

I1

B

I2

C