Rescue concurrent counter repair

javaEXTREMECODING

Rescue concurrent counter repair

Extreme Java arena: AtomicInteger, synchronization, and race-condition reasoning

XP reward

575

Coins

Target time

69m

Mission locked

Missing prerequisites: java-easy-concurrent-counter

Metrics counters are missing increments during high-concurrency tests. You are working inside a Java backend interview lab, and the arena only clears when the result is safe, deterministic, and explainable.

Learning objective

Learn to apply AtomicInteger, synchronization, and race-condition reasoning in a Java backend interview lab while explaining the invariant, safety constraints, and hidden edge cases.

Mission order

Multiple threads call increment, add, snapshot, and reset. Minimize blast radius, make the result auditable, and explain the tradeoff you chose. Submit the solution plus enough reasoning to pass hidden edge cases.

Visible checks

sample case

Expected: 2

empty input

Expected: 0

Clear requirements

Demonstrates AtomicInteger, synchronization, and race-condition reasoning
Handles the visible sample and hidden edge cases
Keeps output deterministic and explainable
Avoids unsafe dynamic execution

Secure validation contract

Judge type

CODING

Complexity target

Meets expected complexity under hidden scale cases

Workspace

Code editor

locked

Clear the route first

You can read the mission brief, but the editor, hints, tests, and submit flow stay locked until progression or plan access catches up.

Enter Immersive

Test Results

Run the visible checks when your first pass is ready.

Clear Protocol

1Read the scenario and restate the expected output shape.

2Run visible checks before chasing hidden edge cases.

3Use Genie for one nudge if stuck, then explain the invariant.

4Submit only when the result is deterministic and safe.

Rewards

575

Coins

Mission Route

Previous Next

Back to catalog

Hints

Hints are metered and logged for No Hint Hero runs.

Genie Mentor Core

Hint protocol / contextual guardrails active

Progressive hints

Failed-test aware

Solution guarded

Mission: java-extreme-concurrent-counter0 attempts0 failed tests0 hints used

Progressive hint depth

Genie: Genie online. I use your mission, attempts, failed tests, hints, and path context to coach the next rep without dumping answers first.

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javaEXTREMECODING