Replace platform threads with virtual threads to fix busy-waiting

[Kaaldut8]

Refactors busy-waiting loops by replacing platform threads with virtual threads and improving concurrency handling across affected components.

Fixes #2977

[github-actions]

PR Summary

Refactors busy-wait loops by replacing platform threads with virtual threads to improve concurrency handling and avoid busy-wait scenarios. Includes formatting enforcement via Spotless across modules, minor formatting tweaks in several modules, and updates to the session-server to use a virtual-thread-based scheduler for session expiration. Also adds license headers to rate-limiting-pattern sources and expands test file formatting for consistency across the project.

Changes

File	Summary
combinator/src/test/java/com/iluwatar/combinator/FinderTest.java	Adjusted the FinderTest multi-line string literal formatting to improve readability and align with the project’s formatting rules.
microservices-self-registration/contextservice/pom.xml	Added Spotless Maven plugin to enforce consistent Java formatting in the contextservice module.
microservices-self-registration/eurekaserver/pom.xml	Added Spotless Maven plugin to enforce consistent Java formatting in the Eurekaserver module.
microservices-self-registration/eurekaserver/src/main/java/com/learning/eurekaserver/EurekaserverApplication.java	Adjusted indentation and formatting of the EurekaserverApplication main method for consistency.
microservices-self-registration/eurekaserver/src/test/java/com/learning/eurekaserver/EurekaserverApplicationTests.java	Improved formatting and comments in the Eurekaserver application tests to match style guidelines.
microservices-self-registration/greetingservice/pom.xml	Added Spotless Maven plugin to enforce formatting in the greetingservice module.
microservices-self-registration/pom.xml	Enabled Spotless formatting checks at the parent module level to enforce consistency across modules.
pom.xml	Simplified Spotless configuration by removing explicit executions and relying on default googleJavaFormat settings.
rate-limiting-pattern/pom.xml	Inserted MIT license header into the rate-limiting-pattern module’s POM to clarify licensing.
rate-limiting-pattern/src/main/java/com/iluwatar/rate/limiting/pattern/AdaptiveRateLimiter.java	Prepended MIT license header to AdaptiveRateLimiter.
rate-limiting-pattern/src/main/java/com/iluwatar/rate/limiting/pattern/App.java	Adjusted App main to correctly instantiate TokenBucketRateLimiter and added license header.
rate-limiting-pattern/src/main/java/com/iluwatar/rate/limiting/pattern/FindCustomerRequest.java	Prepended MIT license header to FindCustomerRequest.java.
rate-limiting-pattern/src/main/java/com/iluwatar/rate/limiting/pattern/FixedWindowRateLimiter.java	Prepended MIT license header to FixedWindowRateLimiter.java.
rate-limiting-pattern/src/main/java/com/iluwatar/rate/limiting/pattern/RateLimitException.java	Prepended MIT license header to RateLimitException.java.
rate-limiting-pattern/src/main/java/com/iluwatar/rate/limiting/pattern/RateLimitOperation.java	Prepended MIT license header to RateLimitOperation.java.
rate-limiting-pattern/src/main/java/com/iluwatar/rate/limiting/pattern/RateLimiter.java	Prepended MIT license header to RateLimiter.java.
rate-limiting-pattern/src/main/java/com/iluwatar/rate/limiting/pattern/ServiceUnavailableException.java	Prepended MIT license header to ServiceUnavailableException.java.
rate-limiting-pattern/src/main/java/com/iluwatar/rate/limiting/pattern/ThrottlingException.java	Prepended MIT license header to ThrottlingException.java.
rate-limiting-pattern/src/main/java/com/iluwatar/rate/limiting/pattern/TokenBucketRateLimiter.java	Refactored TokenBucketRateLimiter: added shutdown, per-bucket lastRefillTime, synchronized tryConsume, and refillIfNeeded to support safe token replenishment and thread-safe consumption.
rate-limiting-pattern/src/test/java/com/iluwatar/rate/limiting/pattern/AdaptiveRateLimiterTest.java	Prepended MIT license header to AdaptiveRateLimiterTest.
rate-limiting-pattern/src/test/java/com/iluwatar/rate/limiting/pattern/AppTest.java	Prepended MIT license header to AppTest.
rate-limiting-pattern/src/test/java/com/iluwatar/rate/limiting/pattern/AppTestUtils.java	Prepended MIT license header to AppTestUtils.
rate-limiting-pattern/src/test/java/com/iluwatar/rate/limiting/pattern/ConcurrencyTests.java	Prepended MIT license header to ConcurrencyTests.
rate-limiting-pattern/src/test/java/com/iluwatar/rate/limiting/pattern/ExceptionTests.java	Prepended MIT license header to ExceptionTests.
rate-limiting-pattern/src/test/java/com/iluwatar/rate/limiting/pattern/FindCustomerRequestTest.java	Prepended MIT license header to FindCustomerRequestTest.
rate-limiting-pattern/src/test/java/com/iluwatar/rate/limiting/pattern/FixedWindowRateLimiterTest.java	Prepended MIT license header to FixedWindowRateLimiterTest.
rate-limiting-pattern/src/test/java/com/iluwatar/rate/limiting/pattern/RateLimitOperationTest.java	Prepended MIT license header to RateLimitOperationTest.
rate-limiting-pattern/src/test/java/com/iluwatar/rate/limiting/pattern/RateLimiterTest.java	Prepended MIT license header to RateLimiterTest.
rate-limiting-pattern/src/test/java/com/iluwatar/rate/limiting/pattern/TokenBucketRateLimiterTest.java	Prepended MIT license header to TokenBucketRateLimiterTest.
server-session/src/main/java/com/iluwatar/sessionserver/App.java	Replaced thread-based session expiration checker with a virtual-thread-based scheduled task and added a shutdown hook; uses a virtual-thread scheduler.

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autogenerated by presubmit.ai

[github-actions]

✅ LGTM!

Review Summary

Commits Considered (1)

• ea68115: Apply Spotless formatting

Files Processed (2)

• rate-limiting-pattern/src/main/java/com/iluwatar/rate/limiting/pattern/App.java (3 hunks)
• rate-limiting-pattern/src/main/java/com/iluwatar/rate/limiting/pattern/TokenBucketRateLimiter.java (2 hunks)

Actionable Comments (0)

Skipped Comments (8)

• rate-limiting-pattern/src/main/java/com/iluwatar/rate/limiting/pattern/App.java [1-25]

  maintainability: "License header added"

• rate-limiting-pattern/src/main/java/com/iluwatar/rate/limiting/pattern/App.java [89-93]

  maintainability: "Initialize TokenBucketRateLimiter outside try for proper cleanup"

• rate-limiting-pattern/src/main/java/com/iluwatar/rate/limiting/pattern/App.java [107-109]

  maintainability: "Ensure TokenBucketRateLimiter is shutdown to avoid thread leaks"

• rate-limiting-pattern/src/main/java/com/iluwatar/rate/limiting/pattern/TokenBucketRateLimiter.java [66-68]

  maintainability: "Expose shutdown for the rate limiter's scheduler"

• rate-limiting-pattern/src/main/java/com/iluwatar/rate/limiting/pattern/TokenBucketRateLimiter.java [74-75]

  design: "Track last refill timestamp for per-second refill policy"

• rate-limiting-pattern/src/main/java/com/iluwatar/rate/limiting/pattern/TokenBucketRateLimiter.java [79-80]

  maintainability: "Initialize refill timestamp during bucket construction"

• rate-limiting-pattern/src/main/java/com/iluwatar/rate/limiting/pattern/TokenBucketRateLimiter.java [82-91]

  concurrency: "Make token consumption synchronized and refilling lazy via refillIfNeeded"

• rate-limiting-pattern/src/main/java/com/iluwatar/rate/limiting/pattern/TokenBucketRateLimiter.java [93-99]

  behavior: "Periodic refill for tokens based on elapsed time"

[github-actions]

🚨 Pull request needs attention.

Review Summary

Commits Considered (1)

• 90b794b: Removes expression which is always true

Files Processed (1)

• rate-limiting-pattern/src/main/java/com/iluwatar/rate/limiting/pattern/App.java (2 hunks)

Actionable Comments (2)

• rate-limiting-pattern/src/main/java/com/iluwatar/rate/limiting/pattern/App.java [89-89]

  possible bug: "Initialize rate limiter variable outside try."

• rate-limiting-pattern/src/main/java/com/iluwatar/rate/limiting/pattern/App.java [91-91]

  possible bug: "Potential risk of null after initialization."

Skipped Comments (1)

• rate-limiting-pattern/src/main/java/com/iluwatar/rate/limiting/pattern/App.java [1-24]

  maintainability: "Add license header to App.java."

[github-actions]

TokenBucketRateLimiter tb = null;

[github-actions]

tb = new TokenBucketRateLimiter(2, 1);

[github-actions]

✅ LGTM!

Review Summary

Commits Considered (1)

• 6d3356e: Add test coverage for sessionserver App

Files Processed (0)

Actionable Comments (0)

Skipped Comments (0)

[sonarqubecloud]

Quality Gate failed

Failed conditions
79.4% Coverage on New Code (required ≥ 80%)

See analysis details on SonarQube Cloud

[github-actions]

This PR is stale because it has been open 60 days with no activity.

[iluwatar]

While the PR correctly attempts to address resource usage, the changes introduced functional bugs in the rate limiter, resource leaks in tests, and broke the educational demonstration of the Twin design pattern.