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What does this PR do?

[github-actions]

PR Summary

This PR adds a Singleton class and its corresponding test file. The Singleton class demonstrates the singleton design pattern, ensuring only one instance of the class exists. The test file verifies the singleton implementation and its functionality.

Changes

File	Summary
visitor/src/main/java/Singleton.java	This file implements the Singleton design pattern. It includes a private constructor, a static method to get the instance, and a sample method showMessage. The class ensures only one instance is created.
visitor/src/test/java/com/iluwatar/visitor/SingletonTest.java	This file contains a JUnit test case for the Singleton class. The test verifies that only one instance of the Singleton class is created and that the showMessage method functions correctly.
visitor/target/classes/Singleton.class	New file.
visitor/target/classes/com/iluwatar/visitor/App.class	New file.
visitor/target/classes/com/iluwatar/visitor/Commander.class	New file.
visitor/target/classes/com/iluwatar/visitor/CommanderVisitor.class	New file.
visitor/target/classes/com/iluwatar/visitor/Sergeant.class	New file.
visitor/target/classes/com/iluwatar/visitor/SergeantVisitor.class	New file.
visitor/target/classes/com/iluwatar/visitor/Soldier.class	New file.
visitor/target/classes/com/iluwatar/visitor/SoldierVisitor.class	New file.
visitor/target/classes/com/iluwatar/visitor/Unit.class	New file.
visitor/target/classes/com/iluwatar/visitor/UnitVisitor.class	New file.

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[github-actions]

🚨 Pull request needs attention.

Review Summary

Commits Considered (1)

• a924177: Add files via upload

Files Processed (12)

• visitor/src/main/java/Singleton.java (1 hunk)
• visitor/src/test/java/com/iluwatar/visitor/SingletonTest.java (1 hunk)
• visitor/target/classes/Singleton.class (0 hunks)
• visitor/target/classes/com/iluwatar/visitor/App.class (0 hunks)
• visitor/target/classes/com/iluwatar/visitor/Commander.class (0 hunks)
• visitor/target/classes/com/iluwatar/visitor/CommanderVisitor.class (0 hunks)
• visitor/target/classes/com/iluwatar/visitor/Sergeant.class (0 hunks)
• visitor/target/classes/com/iluwatar/visitor/SergeantVisitor.class (0 hunks)
• visitor/target/classes/com/iluwatar/visitor/Soldier.class (0 hunks)
• visitor/target/classes/com/iluwatar/visitor/SoldierVisitor.class (0 hunks)
• visitor/target/classes/com/iluwatar/visitor/Unit.class (0 hunks)
• visitor/target/classes/com/iluwatar/visitor/UnitVisitor.class (0 hunks)

Actionable Comments (1)

• visitor/src/test/java/com/iluwatar/visitor/SingletonTest.java [21-23]

  bug: "Incorrect assertion method used."

Skipped Comments (0)

[github-actions]

The assertSame method in SingletonTest is not a standard JUnit assertion. Replace it with assertEquals or assertSame from JUnit's assertion library.