What state does a Java thread enter when it is waiting to acquire a monitor lock to enter a synchronized block or method?
Option C is correct. A thread is in BLOCKED state when it is waiting for a monitor lock to enter/re-enter a synchronized block or method.
Which keyword in Java prevents a class from being subclassed or a method from being overridden?
Option B is correct. A final class cannot be extended (e.g. String class), and a final method cannot be overridden by subclasses.
What is the default initial capacity and load factor of a HashMap in Java if not specified during instantiation?
Option A is correct. Default initial capacity of HashMap is 16 buckets, and the default load factor is 0.75 (rehash triggers when 75% capacity is reached).
Which class in java.util provides a resizable array-based implementation of Deque and Queue interfaces with no capacity restrictions?
Option C is correct. ArrayDeque implements Deque using a resizable array. It is faster than Stack when used as a stack and faster than LinkedList when used as a queue.
Which Java 8 feature allows collection operations to be processed concurrently across multiple threads automatically?
Option C is correct. parallelStream() splits stream data into multiple substreams processed concurrently across available CPU cores using the ForkJoinPool.