OOP & Design Patterns - Singleton Pattern - Thread Safety, Double-Checked Locking & Lazy Init
What is the space complexity of implementing a thread-safe Singleton using double-checked locking with a volatile instance variable in Java?
What is the space complexity of implementing a thread-safe Singleton using double-checked locking with a volatile instance variable in Java?
medium🪤 Complexity Trap Q6 of Q15
Step-by-Step Solution
Solution:
Step 1: Identify space used by Singleton instance and lock
Singleton instance and lock are constant space O(1).Step 2: Consider volatile keyword overhead
Volatile adds metadata and memory fencing, which is negligible but not zero; however, no extra space proportional to n.Final Answer:
Option B -> Option BQuick Check:
Space is constant, volatile adds minor overhead, often considered O(1) [OK]
Quick Trick: Singleton uses constant space; volatile adds negligible overhead [OK]
Common Mistakes:
MISTAKES- Assuming synchronization or threads increase space linearly
Trap Explanation:
PITFALL- Candidates confuse synchronization overhead with space complexity, which is constant.
Interviewer Note:
CONTEXT- Tests understanding of space complexity including volatile and synchronization
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