Add Java Hello World demo project

[Copilot]

Adds a minimal Maven-based Java project demonstrating a Hello World program, suitable for workshop demos.

Structure

• java-hello-world/pom.xml — Maven build, Java 17, JUnit Jupiter 5.10.2
• src/main/java/com/example/HelloWorld.java — greet(String name) with null/blank fallback + main entry point
• src/test/java/com/example/HelloWorldTest.java — 4 unit tests covering standard, custom name, null, and blank inputs

Usage

cd java-hello-world
mvn clean package
java -jar target/java-hello-world-1.0.0.jar  # → Hello, World!

Notes

• .gitignore updated to exclude Java build artifacts (*.class, *.jar, *.war, *.ear, target/)
• greet() defaults to "World" on null or blank input rather than throwing NullPointerException

Original prompt

help me create a new java project that is basically used to demo hello world

Created from VS Code.

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