D286 Java Fundamentals - Set 4 - Part 2

Correct Answer: IOException

IOException is checked, so it must be caught or declared. The others extend RuntimeException and are unchecked.

Correct Answer: The checked exceptions the method may propagate to its caller

The throws clause declares which checked exceptions may escape the method, requiring callers to handle or further declare them.

Correct Answer: Yes, each handling a different exception type

Multiple catch blocks may follow a try, each handling a specific exception type. They are evaluated in order, so more specific types must come first.

Correct Answer: A compile error occurs because the subclass catch is unreachable

A broader catch placed first would handle the subclass exception, making the later specific block unreachable, which the compiler rejects.

Correct Answer: A user-defined class extending Exception or RuntimeException

Custom exceptions extend Exception or RuntimeException to represent domain-specific error conditions with meaningful names and additional context.

Correct Answer: Marking a class whose objects can be converted to a byte stream

Serializable is a marker interface indicating that a class's objects may be serialized into a byte stream for storage or transmission.

Correct Answer: A sequence of elements supporting functional-style operations

The Stream API processes sequences of elements with functional operations such as filter, map, and reduce, often more expressively than explicit loops.

Correct Answer: Retains only elements matching a given predicate

filter() takes a predicate and produces a stream containing only the elements for which the predicate returns true.

Correct Answer: Transforms each element using a supplied function

map() applies a function to each element, producing a new stream of the transformed results, leaving the source unchanged.

Correct Answer: Intermediate operations execute only when a terminal operation runs

Intermediate operations build a pipeline without processing elements. Work begins only when a terminal operation such as collect() or forEach() is invoked.

Correct Answer: Representing a value that may or may not be present, avoiding null

Optional explicitly models the possible absence of a value, encouraging callers to handle the empty case rather than risking a NullPointerException.

Correct Answer: An independent path of execution within a program

A thread is a separate flow of execution allowing concurrent work within a single program, such as keeping a user interface responsive during long operations.

Correct Answer: start()

Calling start() creates a new thread and invokes run() on it. Calling run() directly executes the code on the current thread instead.

Correct Answer: Incorrect behavior caused by unsynchronized concurrent access to shared data

A race condition occurs when multiple threads access shared mutable state concurrently and the result depends on unpredictable timing of their execution.

Correct Answer: Mutual exclusion so only one thread executes the block at a time

The synchronized keyword acquires a lock so only one thread at a time executes the protected code, preventing concurrent corruption of shared state.

Correct Answer: Their state cannot change, so concurrent reads are always safe

Because immutable objects never change after construction, multiple threads can read them concurrently with no risk of inconsistent state or need for synchronization.

Correct Answer: Generating sequences of pseudorandom numbers

Random generates pseudorandom values of various types. For security-sensitive purposes, SecureRandom should be used instead.

Correct Answer: A date without time or time zone information

LocalDate represents a calendar date such as 2026-07-23 with no time-of-day or time zone component, part of the modern java.time API.

Correct Answer: Immutable, thread-safe classes with a clearer domain model

The java.time classes are immutable and thread-safe with a clear separation of concepts, resolving longstanding design problems in the legacy Date and Calendar classes.

Correct Answer: Providing a one-off implementation of an interface or class inline

An anonymous inner class defines and instantiates an implementation in a single expression, useful for short one-time implementations, now often replaced by lambdas.