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Groovy / Collections

WithIndex

Learn WithIndex in Groovy through a focused explanation, a dedicated topic-specific example, an engineering boundary, and a mastery check.

12 min read • Intermediate

WithIndex is a focused Groovy lesson inside Collections. The example uses the construct named in the lesson directly rather than reusing a generic placeholder.

Trace the example from its inputs through WithIndex and identify the behavior that would change if that construct were removed or replaced. Pay attention to the language-specific rules shown by the syntax, because neighboring lessons intentionally exercise different mechanisms.

Topic-specific example

groovy-0039-5345f022e5.groovy
groovy Try It Live 
def sample40 = [40, 41, 42]
println sample40.sum() // WithIndex
Edge case / engineering note

For WithIndex, test one realistic boundary: empty data, invalid input, unavailable resources, lifetime/cleanup, type constraints, or concurrency timing where applicable. A successful happy path is not enough to prove the construct is used correctly.

Content source & attribution
Original Syntaxis Content · Original Syntaxis Content

Lesson quizzes

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Flatten nested collections