The answer is to replace LinkedBlockingQueue with a PriorityBlockingQueue that orders by timestamp. This is correct because PriorityBlockingQueue internally maintains elements in their natural order or according to a provided Comparator, so ticks are automatically sorted by timestamp upon insertion, ensuring the consumer always dequeues the chronologically earliest tick first even when multiple producer threads introduce out-of-order arrivals due to network delays. On the Oracle Certified Professional Java SE 17 Developer 1Z0-829 exam, this question tests your understanding of concurrent collections and the trade-off between ordering guarantees and throughput—a common trap is to add explicit sorting or synchronization, which sacrifices performance. Remember that PriorityBlockingQueue combines thread safety with automatic ordering, making it ideal for scenarios like high-frequency trading where message ordering must be preserved without blocking producers. Memory tip: think "Priority = Priority ordering, Blocking = Thread-safe queue."
1Z0-829 Controlling Program Flow Practice Question
This 1Z0-829 practice question tests your understanding of controlling program flow. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
You are developing a high-frequency trading application that processes a stream of market data ticks. Each tick is represented by a Tick object with fields: long timestamp, String symbol, double price, int volume. Ticks arrive in real-time and must be processed in order. A bug is reported: the application occasionally processes a tick out of order, causing incorrect trade decisions. The processing logic uses a while loop to read from a blocking queue and process each tick. The code is:
BlockingQueue<Tick> queue = new LinkedBlockingQueue<>();
while (true) {
Tick tick = queue.take();
process(tick);
}
After investigation, you find that the queue is fed by multiple producer threads that sometimes reorder ticks due to network delays. Which course of action best ensures ticks are processed in the correct chronological order without sacrificing throughput?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Replace LinkedBlockingQueue with a PriorityBlockingQueue that orders by timestamp.
Option C is correct because PriorityBlockingQueue maintains elements in natural order (or by a provided Comparator), so ticks are automatically ordered by timestamp when inserted. This ensures the consumer always processes the chronologically earliest tick first, even if producers add them out of order, without requiring additional sorting or blocking.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Use a SynchronousQueue and have producers wait for the consumer to acknowledge.
Why it's wrong here
SynchronousQueue does not buffer; it would not help reordering.
✗
After taking from the queue, sort a batch of ticks before processing.
Why it's wrong here
Does not prevent reordering and adds complexity.
✓
Replace LinkedBlockingQueue with a PriorityBlockingQueue that orders by timestamp.
Why this is correct
PriorityBlockingQueue maintains ordering by timestamp.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Add a delay before processing to allow out-of-order ticks to arrive.
Why it's wrong here
Introduces latency and does not guarantee order.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may think sorting after retrieval (Option B) is sufficient, but they overlook that PriorityBlockingQueue provides automatic ordering at insertion time, which is more efficient and maintains correctness without batching delays.
Detailed technical explanation
How to think about this question
PriorityBlockingQueue uses a binary heap internally, offering O(log n) insertion and removal, which is efficient for high-frequency trading where thousands of ticks per second must be ordered. The Comparator can be tuned to break ties (e.g., by symbol or sequence number) to ensure deterministic ordering. In real-world systems, using a PriorityBlockingQueue with a timestamp-based comparator is a common pattern for handling out-of-order data streams in event-driven architectures.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Controlling Program Flow — This question tests Controlling Program Flow — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Replace LinkedBlockingQueue with a PriorityBlockingQueue that orders by timestamp. — Option C is correct because PriorityBlockingQueue maintains elements in natural order (or by a provided Comparator), so ticks are automatically ordered by timestamp when inserted. This ensures the consumer always processes the chronologically earliest tick first, even if producers add them out of order, without requiring additional sorting or blocking.
What should I do if I get this 1Z0-829 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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