[Solved] Identify the error in this Kafka Streams code snippet: var result = orders .groupBy(order -> order.customerId) .count(); | Kafka

Kafka - Streams

Identify the error in this Kafka Streams code snippet:

var result = orders
  .groupBy(order -> order.customerId)
  .count();

AMissing a filter() before groupBy.

Bcount() cannot be called after groupBy.

CThe variable 'orders' must be a KTable, not a KStream.

DgroupBy requires a key-value mapper, not a single argument.

Step-by-Step Solution

Solution:

Step 1: Check groupBy method signature
groupBy expects a function with two parameters: key and value, e.g., (key, value) -> newKey.
Step 2: Identify incorrect lambda usage
The code uses a single-argument lambda order -> order.customerId, which is invalid for groupBy.
Final Answer:
groupBy requires a key-value mapper, not a single argument. -> Option D
Quick Check:
groupBy needs (key, value) -> newKey [OK]

Quick Trick: groupBy needs two parameters in lambda [OK]

Common Mistakes:

MISTAKES

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