Description

Implements comprehensive demo for JEP 361 - Switch Expressions (Java 14), along with linking classes for the preview versions in Java 12 (JEP 325) and Java 13 (JEP 354).

Closes #318

Changes

Main Demo (Java 14 - JEP 361)

• Created SwitchExpressionsDemo.java with comprehensive demonstrations of:
  • Arrow labels (case ... ->) vs traditional labels
  • Switch expressions - using switch as an expression to assign values
  • Yield statement - for complex logic blocks within switch expressions
  • Multiple constants per case - comma-separated values
  • Exhaustiveness checking - especially with enums

Linking Classes

• Java 12 - JEP 325: Created SwitchExpressionsPreview.java (first preview with break statement)
• Java 13 - JEP 354: Created SwitchExpressionsSecondPreview.java (second preview introducing yield)

Metadata & Registration

• Updated JDK14Info.json with JEP 361 entry
• Created JDK13Info.json (first Java 13 metadata file) with JEP 354 entry
• Updated JDK12Info.json with JEP 325 entry
• Registered all demos in respective DemoLoader classes

Demo Features Showcased

The JEP 361 demo includes 5 comprehensive demonstrations:

1. demonstrateArrowLabels() - Contrast between traditional switch with fall-through and new arrow syntax
2. demonstrateSwitchExpression() - Old vs new way of using switch to assign values
3. demonstrateYieldStatement() - Using yield for complex logic in switch expressions
4. demonstrateMultipleConstants() - Multiple case values with practical example
5. demonstrateExhaustiveness() - Exhaustiveness checking with enum examples

Evolution Across Java Versions

This PR properly documents the evolution of switch expressions:

• JDK 12 (JEP 325): First preview - arrow labels, switch expressions with break <value>
• JDK 13 (JEP 354): Second preview - introduced yield statement replacing break <value>
• JDK 14 (JEP 361): Final version - no changes, became permanent feature

All three classes are properly cross-referenced using @see annotations.

Checklist

• Follows package structure: org.javademos.java{12,13,14}.jep{325,354,361}
• Implements IDemo interface with proper info() and demo() methods
• Uses Markdown-style documentation (///)
• Added JSON entries to JDK12Info.json, JDK13Info.json, and JDK14Info.json
• Registered in Java12DemoLoader, Java13DemoLoader, and Java14DemoLoader using JEP numbers as keys
• Includes @author attribution
• Working code examples covering all major features
• Proper cross-references between related JEPs using @see annotations
• Link classes properly reference final implementation