1Z0-829 Controlling Program Flow Practice Question
A financial application processes a daily batch of 10 million transactions. Each transaction is an object with fields: id, amount, and status (an enum: PENDING, APPROVED, REJECTED). The requirement is to find the first APPROVED transaction with amount greater than 1000. The current implementation uses a while loop with a nested if-else structure that checks each transaction sequentially. The loop also logs each transaction status, which involves a moderately expensive file write operation. Performance analysis shows the method is a bottleneck, often taking over 12 seconds. The development team is considering refactoring. Which course of action will most effectively reduce execution time while maintaining the requirement?
⚠ Common exam trap
In an Oracle Java exam, the trap is that candidates focus on loop structure (while vs for vs recursion) or parallelism, but overlook the real bottleneck: the expensive file write operation inside the loop, which must be removed or deferred to achieve significant performance gains.
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 the while loop with a traditional for loop that uses a break when the first match is found, and defer the logging to a separate batch process after the loop.
It removes the expensive file write operation from the loop, which is the primary cause of the bottleneck. By deferring logging to a separate batch process, the loop can iterate quickly and break immediately upon finding the first APPROVED transaction with amount > 1000, drastically reducing execution time while still meeting the requirement.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Refactor the while loop into a recursive method that processes one transaction per call and stops when the condition is met.
Why it's wrong here
Recursion adds method call overhead and risk of stack overflow for large datasets; not an optimization.
- ✗
Replace the while loop with a parallel stream and use findFirst() to get the first matching transaction.
Why it's wrong here
Parallel streams introduce synchronization overhead and may not preserve encounter order efficiently, making it slower for this sequential search.
- ✗
Replace the while loop with a for-each loop that breaks when the condition is met, but keep the logging inside the loop.
Why it's wrong here
The break improves performance but the logging I/O still occurs for all transactions until the match is found, which is the main bottleneck.
- ✓
Replace the while loop with a traditional for loop that uses a break when the first match is found, and defer the logging to a separate batch process after the loop.
Why this is correct
Early break reduces iterations, and removing logging I/O from the loop drastically improves performance. Batch logging can be done asynchronously.
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