Analyze the code: try { return 5; } finally { return 10; } What will be returned?

The correct answer is B: 10. The finally block always executes, and if it contains a return statement, it overrides the return value from try or catch block. So 10 is returned.

What happens when you use raw type List instead of List?

The correct answer is D: All of the above. Using raw types bypasses generic type checking, losing type safety. Elements are treated as Object at runtime, potentially causing ClassCastException when casting.

Which of the following best describes CyclicBarrier?

The correct answer is A: It allows N threads to wait for each other at a barrier point. CyclicBarrier is a synchronizer that allows a fixed number of threads to wait for each other at a barrier point. Once all threads reach the barrier, they proceed together. It's reusable (cyclic) unlike CountDownLatch.

What is the purpose of the strictfp modifier in the context of multithreading?

The correct answer is A: Ensures consistent floating-point calculations across platforms. strictfp ensures consistent floating-point results across different platforms/JVMs, though it's not directly a multithreading construct.

Consider the following code: int x = 5; x += 3; System.out.println(x); What is the output?

The correct answer is B: 8. The += operator is an assignment operator that adds the right operand to the left operand and assigns the result. So x += 3 means x = x + 3, which is 5 + 3 = 8.

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Java Programming

Java OOP, collections, multithreading

212 Q 10 Topics Take Mock Test

Difficulty: All Easy Medium Hard 151–160 of 212

Topics in Java Programming

All Basics & Syntax 100 OOP in Java 100 Collections Framework 100 Multithreading 100 Exception Handling 100 I/O Streams 100 JDBC 100 Generics 100 Lambda Expressions 100 Spring Framework Basics 58

Q.151 Hard Collections Framework

Which method in Collections can create a thread-safe Map from a non-thread-safe Map?

A Collections.synchronizedMap()

B Collections.synchronizedList()

C new ConcurrentHashMap()

D Collections.unmodifiableMap()

Correct Answer: A. Collections.synchronizedMap()

EXPLANATION

Collections.synchronizedMap() wraps a Map with synchronized access. However, iteration still requires external synchronization.

Test

Q.152 Hard Collections Framework

In Java 2024-25, which enhancement improved record support in collections?

A Records automatically implement Comparable

B Records can be used as sealed collection types with pattern matching

C Records eliminate the need for custom Comparators

D Records are automatically thread-safe

Correct Answer: B. Records can be used as sealed collection types with pattern matching

EXPLANATION

Java 21+ enhanced sealed classes and pattern matching, allowing records to be used with pattern matching in collection operations and switch statements for type-safe data handling.

Test

Q.153 Hard Collections Framework

Which of these operations is guaranteed to be atomic in ConcurrentHashMap?

A if(!map.containsKey(key)) map.put(key, value);

B map.putIfAbsent(key, value);

C map.get(key) followed by map.put(key, newValue);

D map.remove(key) followed by map.put(key, value);

Correct Answer: B. map.putIfAbsent(key, value);

EXPLANATION

putIfAbsent() is an atomic operation. Options A and C-D are compound operations that are not atomic and can have race conditions between checks and modifications.

Test

Q.154 Hard Collections Framework

What is the behavior of WeakHashMap when a key is no longer strongly referenced?

A The entry remains in the map forever

B The entry is eligible for garbage collection

C A NullPointerException is thrown

D The key is automatically reset to null

Correct Answer: B. The entry is eligible for garbage collection

EXPLANATION

WeakHashMap uses weak references for keys. When a key is no longer strongly referenced elsewhere, it becomes eligible for garbage collection, and its entry is removed from the map.

Test

Q.155 Hard Collections Framework

How does Java 8+ handle hash collisions in HashMap differently?

A Uses double hashing

B Converts bucket linked list to Red-Black tree when size exceeds threshold

C Increases hash table size automatically

D Uses linear probing

Correct Answer: B. Converts bucket linked list to Red-Black tree when size exceeds threshold

EXPLANATION

Java 8+ introduced tree nodes: when a bucket's linked list size exceeds TREEIFY_THRESHOLD (8), it converts to a Red-Black tree for better performance (O(log n) vs O(n)).

Test

Q.156 Hard Collections Framework

What does the containsAll() method of Collection return for an empty collection?

A true

B false

C null

D throws exception

Correct Answer: A. true

EXPLANATION

containsAll() returns true for empty collections because mathematically, all elements of an empty set are contained in any set (vacuous truth).

Test

Q.157 Hard Collections Framework

What does the spliterator() method introduced in Java 8 provide over Iterator?

A Better support for parallel processing

B Faster sequential iteration

C Backward iteration capability

D Automatic synchronization

Correct Answer: A. Better support for parallel processing

EXPLANATION

Spliterator provides split() capability enabling efficient parallel stream processing with characteristics advertisement.

Test

Q.158 Hard Collections Framework

In a scenario where you need to maintain a mapping with LRU (Least Recently Used) eviction policy, which class should be extended?

A LinkedHashMap with override of removeEldestEntry()

B TreeMap

C WeakHashMap

D ConcurrentHashMap

Correct Answer: A. LinkedHashMap with override of removeEldestEntry()

EXPLANATION

LinkedHashMap can be extended and removeEldestEntry() overridden to implement LRU cache eviction policy.

Test

Q.159 Hard Collections Framework

What is the worst-case time complexity of QuickSort when used with Collections.sort()?

A O(n log n)

B O(n²)

C O(n)

D O(log n)

Correct Answer: B. O(n²)

EXPLANATION

Collections.sort() uses TimSort (hybrid of merge and insertion sort) with O(n log n) worst-case, but QuickSort's worst-case is O(n²).

Test

Q.160 Hard Collections Framework

Which stream terminal operation preserves encounter order in parallel streams for Collections?

A collect() with unordered Collector

B collect() with CONCURRENT and UNORDERED characteristics

C forEach() directly

D forEachOrdered()

Correct Answer: D. forEachOrdered()

EXPLANATION

forEachOrdered() preserves encounter order even in parallel streams, while forEach() doesn't guarantee order.

Test

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