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MIGRATION_NOTES.md

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Migration Notes: Java 9 → Java 11

Java Version Change

  • From: Java 9 (source/target 1.9)
  • To: Java 11 (using <release>11</release>)
  • The <release> flag replaces the legacy <source>/<target> configuration and provides stronger cross-compilation guarantees.

Plugin Upgrades

Plugin Old Version New Version Notes
maven-compiler-plugin 3.1 3.11.0 Switched from source/target to release flag
maven-surefire-plugin (none) 3.2.5 Added for test execution
maven-failsafe-plugin (none) 3.2.5 Added for integration test support
maven-enforcer-plugin (none) 3.5.0 Added to enforce Java 11+ at build time
maven-javadoc-plugin (none) 3.6.3 Added with <doclint>none</doclint> (Java 11 doclint is stricter)
maven-shade-plugin (unversioned) 3.6.2 Pinned explicit version (was unversioned, which Maven warns is unstable)

Build encoding is pinned to UTF-8 for both source (project.build.sourceEncoding) and reporting (project.reporting.outputEncoding).

Dependency Upgrades

Dependency Old Version New Version Notes
JUnit 4.11 4.13.2 Latest JUnit 4.x; added <scope>test</scope>
JMH (jmh-core) 1.17.4 1.37 Java 11 compatible
JMH (jmh-generator-annprocess) 1.17.4 1.37 Java 11 compatible

Code Fixes Required

Minimal changes were needed:

  • Moved ReadPositiveIntParam.java from src/main/java to src/test/java — this file contained JUnit @Test annotations but was incorrectly placed in the main source tree. With JUnit correctly scoped to test, it must reside under src/test/java.
  • No Nashorn JavaScript engine references found
  • No internal sun.* or com.sun.* API usage
  • No Java EE modules (removed in Java 11) were used
  • Deprecation warning in Util.java (deprecated API usage) — informational only, no breaking change

New Test Coverage

Added integration tests covering core chapters:

Test File Chapter Coverage
FilteringApplesTest.java Chapter 1 Lambda expressions, method references, Predicate-based filtering
StreamBasicsTest.java Chapter 4 Stream creation, filtering, sorting, Java 7 vs Java 8 comparison
StreamProcessingTest.java Chapter 5 Trader/Transaction queries, reduce, distinct, anyMatch
OptionalTest.java Chapter 10 Optional creation, map, flatMap, orElse, filter, stream()
CompletableFutureTest.java Chapter 11 supplyAsync, thenApply, thenCombine, thenCompose, exceptionally
DateTimeTest.java Chapter 12 LocalDate, LocalTime, LocalDateTime, Duration, TemporalAdjusters, DateTimeFormatter

CI Workflow Added

  • GitHub Actions workflow (.github/workflows/ci.yml)
  • Triggers on push/PR to master/main branches
  • Uses Temurin JDK 11 with Maven caching
  • Runs mvn -B clean compile and mvn -B test