1Z0-811 Primitives, Strings and Operators Practice Question
A social media platform processes user login requests. Each request generates a welcome message by concatenating the username with a fixed greeting using the + operator inside a loop that runs hundreds of times per second for thousands of users. The development team notices that the application suffers from high memory consumption and slow response times under load. They profile the code and discover that the method building the welcome message is a bottleneck. The team considers several options to improve performance while maintaining thread safety. Which approach should the team implement?
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 string concatenation with StringBuilder and allocate an initial capacity large enough to hold the final message.
StringBuilder with sufficient initial capacity reduces memory reallocations and is faster than StringBuffer for single-threaded contexts. Option A (StringBuffer) is thread-safe but slower due to synchronization, not needed here since the method is not shared across threads. Option C (concat()) still creates new strings internally, similar to + operator. Option D (intern()) does not improve performance and may cause memory issues.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Replace string concatenation with StringBuffer and use an initial capacity to minimize resizing.
Why it's wrong here
Flawed: StringBuffer is synchronized, adding overhead without thread-safety need.
- ✓
Replace string concatenation with StringBuilder and allocate an initial capacity large enough to hold the final message.
Why this is correct
Correct: StringBuilder is efficient and non-synchronized; initial capacity avoids resizing.
- ✗
Keep using the + operator but call intern() on the resulting string to reuse memory.
Why it's wrong here
Flawed: intern() adds overhead and does not reduce object creation in the loop.
- ✗
Replace string concatenation with the concat() method called on the greeting string.
Why it's wrong here
Flawed: concat() still creates a new String, not improving performance significantly.
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