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Consider the following code snippet using the Strategy Pattern. What will be the output when processor.pay(0) is called with UPIStrategy?

medium🧾 Code Trace Q4 of Q15

OOP & Design Patterns - Strategy Pattern - Replace Conditionals with Polymorphism

Consider the following code snippet using the Strategy Pattern. What will be the output when processor.pay(0) is called with UPIStrategy?

AError: Amount must be positive

BProcessing UPI payment of $0

CNo output

DProcessing UPI payment of $0

Step-by-Step Solution

Solution:

Step 1: Trace method call with zero amount
UPIStrategy.pay is called with amount=0, which is valid and prints the message.
Step 2: Confirm output
The print statement outputs "Processing UPI payment of $0" exactly.
Final Answer:
Option B -> Option B
Quick Check:
Zero amount is handled by printing message [OK]

Quick Trick: Zero amount still triggers print in strategy method [OK]

Common Mistakes:

MISTAKES

Assuming error on zero amount
Confusing output with no output

Trap Explanation:

PITFALL

Candidates expect error or no output on zero amount, but code prints message.

Interviewer Note:

CONTEXT

Tests boundary input handling in polymorphic methods.

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