Design patterns · interview question
A code review describes a ConfigManager singleton. Highlight the statements that describe real problems.
Highlight textHard
Select the findings that apply.
Answer and explanation
Correct answer
- getInstance() checks whether instance is null and creates it, with no synchronization, and it's called from many request threads at startup.
- The class implements Serializable but has no readResolve() method.
Why
Safe options: an enum singleton, eager initialization (private static final), or the holder-class idiom. Each avoids races without explicit locking.
References
- Joshua Bloch, Effective Java, 3rd ed. (2018)
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