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Which design pattern ensures a class has only one instance and provides a global point of access, while also delaying instance creation until it is first needed with thread safety?

easy💻 Programming Q1 of Q15

OOP & Design Patterns - Singleton Pattern - Thread Safety, Double-Checked Locking & Lazy Init

Which design pattern ensures a class has only one instance and provides a global point of access, while also delaying instance creation until it is first needed with thread safety?

AThread-safe Lazy Singleton Pattern

BFactory Pattern

CObserver Pattern

DPrototype Pattern

Step-by-Step Solution

Solution:

Step 1: Understand Singleton Pattern
The Singleton pattern restricts instantiation of a class to one object and provides a global access point.
Step 2: Lazy Initialization
Lazy initialization means the instance is created only when first requested, not at class loading.
Step 3: Thread Safety
Thread safety ensures that multiple threads do not create multiple instances simultaneously.
Final Answer:
Option A -> Option A
Quick Check:
Singleton + Lazy + Thread Safety = Thread-safe Lazy Singleton [OK]

Quick Trick: Singleton with lazy init and thread safety fits best [OK]

Common Mistakes:

MISTAKES

Confusing Factory with Singleton
Ignoring thread safety in lazy init
Choosing patterns unrelated to instance control

Trap Explanation:

PITFALL

Factory creates multiple instances; Observer and Prototype do not guarantee single instance.

Interviewer Note:

CONTEXT

Tests understanding of Singleton pattern with lazy initialization and thread safety.

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