Today we dove deep into JVM architecture while transforming our Library Management System to embrace immutability.

The code changes from this session can be found here.

Day 7 Summary

Overview

Explored JVM architecture through our practical projects while evolving the Library Management System to use immutable records for state management.

Environment & Tools

  • Proper Java version management (OpenJDK 21)
  • Git workflow
  • Package structure and compilation
  • JVM verbose class loading

Concepts Covered

JVM Architecture

  • Class loading lifecycle
  • Dynamic class loading patterns
  • Memory management principles
  • Garbage collection basics

Immutability Patterns

  • Record types for borrowing events
  • State vs Event sourcing
  • Clean separation of concerns
  • Audit trail implementation

System Evolution

  • Removed mutable state from BookCopy
  • Introduced BorrowingRecord
  • Enhanced BorrowingService responsibilities
  • Improved interface segregation

Resource Management

  • Proper datetime formatting
  • String representation patterns
  • Efficient optional handling
  • History tracking implementation

Implementation Progress

  • Created immutable BorrowingRecord
  • Updated BorrowingService for history tracking
  • Simplified BookCopy class
  • Enhanced system observability
  • Improved separation of concerns

Key Takeaways

  • JVM’s efficient handling of immutable objects
  • Benefits of event-sourced state management
  • Clean separation of responsibilities
  • Importance of proper version management
  • Value of comprehensive audit trails

Next Steps

Ready to explore:

  • Advanced data structures
  • Algorithms fundamentals
  • Collection framework deep dive
  • Implementation patterns

Master’s Reflection

The apprentice demonstrated excellent judgment in system design, particularly in recognizing the benefits of moving from state-based to event-sourced architecture. The thoughtful approach to immutability and clean separation of concerns suggests a strong grasp of Java’s strengths. The curiosity about JVM internals while maintaining focus on practical implementation shows a balanced learning approach.