- A
Use a SynchronousQueue and have producers wait for the consumer to acknowledge.
Why wrong: SynchronousQueue does not buffer; it would not help reordering.
- B
After taking from the queue, sort a batch of ticks before processing.
Why wrong: Does not prevent reordering and adds complexity.
- C
Replace LinkedBlockingQueue with a PriorityBlockingQueue that orders by timestamp.
PriorityBlockingQueue maintains ordering by timestamp.
- D
Add a delay before processing to allow out-of-order ticks to arrive.
Why wrong: Introduces latency and does not guarantee order.
Question 347 of 519
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?
Answer choices
Why each option matters
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.
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 practitioner preparing for the 1Z0-829 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this 1Z0-829 question test?
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
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