Fix Singleton typo and extend reflection handling to remaining implementations

[smile-ab]

Description:
Fix typo and extend reflection handling for remaining implementations for the Singleton pattern

Issue:
#3202

[github-actions]

PR Summary

This PR fixes a typo and extends reflection handling to several Singleton implementations. It adds exception handling to prevent instantiation via reflection in BillPughImplementation, InitializingOnDemandHolderIdiom, and IvoryTower. Additionally, it includes new tests for reflection-based instantiation in SingletonTest and EnumIvoryTowerTest.

Changes

File	Summary
singleton/src/main/java/com/iluwatar/singleton/BillPughImplementation.java	Added exception handling to the private constructor to prevent instantiation via reflection. Throws IllegalStateException if already initialized.
singleton/src/main/java/com/iluwatar/singleton/InitializingOnDemandHolderIdiom.java	Added exception handling to the private constructor to prevent instantiation via reflection. Throws IllegalStateException if already initialized.
singleton/src/main/java/com/iluwatar/singleton/IvoryTower.java	Added exception handling to the private constructor to prevent instantiation via reflection. Throws IllegalStateException if already initialized.
singleton/src/test/java/com/iluwatar/singleton/EnumIvoryTowerTest.java	Added a test case to verify that creating a new instance via reflection throws an exception. Uses assertThrows to check for ReflectiveOperationException.
singleton/src/test/java/com/iluwatar/singleton/SingletonTest.java	Added a test case to verify that creating a new instance via reflection throws an exception. Uses assertThrows to check for InvocationTargetException.
singleton/src/test/java/com/iluwatar/singleton/ThreadSafeDoubleCheckLockingTest.java	No changes were made to the functionality of this file.

---

autogenerated by presubmit.ai

[github-actions]

✅ LGTM!

Review Summary

Commits Considered (2)

• b8ea511: adding Reflection handling to other Singleton implementations
• d63b5e6: fix typo

Files Processed (6)

• singleton/src/main/java/com/iluwatar/singleton/BillPughImplementation.java (1 hunk)
• singleton/src/main/java/com/iluwatar/singleton/InitializingOnDemandHolderIdiom.java (1 hunk)
• singleton/src/main/java/com/iluwatar/singleton/IvoryTower.java (1 hunk)
• singleton/src/test/java/com/iluwatar/singleton/EnumIvoryTowerTest.java (2 hunks)
• singleton/src/test/java/com/iluwatar/singleton/SingletonTest.java (2 hunks)
• singleton/src/test/java/com/iluwatar/singleton/ThreadSafeDoubleCheckLockingTest.java (2 hunks)

Actionable Comments (0)

Skipped Comments (3)

• singleton/src/main/java/com/iluwatar/singleton/BillPughImplementation.java [42-46]

  readability: "Remove redundant comment."

• singleton/src/main/java/com/iluwatar/singleton/InitializingOnDemandHolderIdiom.java [45-49]

  readability: "Remove redundant comment."

• singleton/src/main/java/com/iluwatar/singleton/IvoryTower.java [35-39]

  readability: "Remove redundant comment."

[github-actions]

✅ LGTM!

Review Summary

Commits Considered (2)

• 28bb7da: adding Reflection handling to other Singleton implementations
• 314f273: fix typo

Files Processed (6)

• singleton/src/main/java/com/iluwatar/singleton/BillPughImplementation.java (1 hunk)
• singleton/src/main/java/com/iluwatar/singleton/InitializingOnDemandHolderIdiom.java (1 hunk)
• singleton/src/main/java/com/iluwatar/singleton/IvoryTower.java (1 hunk)
• singleton/src/test/java/com/iluwatar/singleton/EnumIvoryTowerTest.java (2 hunks)
• singleton/src/test/java/com/iluwatar/singleton/SingletonTest.java (2 hunks)
• singleton/src/test/java/com/iluwatar/singleton/ThreadSafeDoubleCheckLockingTest.java (2 hunks)

Actionable Comments (0)

Skipped Comments (3)

• singleton/src/main/java/com/iluwatar/singleton/BillPughImplementation.java [42-46]

  readability: "Remove redundant comment."

• singleton/src/main/java/com/iluwatar/singleton/InitializingOnDemandHolderIdiom.java [45-49]

  readability: "Remove redundant comment."

• singleton/src/main/java/com/iluwatar/singleton/IvoryTower.java [35-39]

  readability: "Remove redundant comment."

[sonarqubecloud]

Quality Gate failed

Failed conditions
B Maintainability Rating on New Code (required ≥ A)

See analysis details on SonarQube Cloud

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[iluwatar]

Looks good! Thank you for the contribution 🎉

@all-contributors please add @smile-ab for code

[allcontributors]

@iluwatar

I've put up a pull request to add @smile-ab! 🎉