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Unit 06 · lesson

Bridge Checkpoint: Three Components, Three Runtime Models

This route assumes you already know Java classes, constructors, fields, methods, and encapsulation.

The bridge question is architectural: when do three things that all look like software components actually belong to different execution models?

Compare:

plain Java object
WPILib subsystem
ROS 2 node

A plain Java object exists inside a JVM process and is evidenced by source, tests, runtime state, or debugger/log output.

A WPILib subsystem is a Java framework component that participates in WPILib conventions and scheduling. It is still not a ROS graph entity.

A ROS 2 node participates in the ROS graph and has middleware-visible relationships such as publishers, subscribers, services, actions, and parameters.

Build the boundary table

For each model, record:

  • runtime owner;
  • how it is created;
  • how another component interacts with it;
  • what evidence proves it exists;
  • one claim that evidence does not prove.

The key rule is simple: similar responsibilities do not make runtime identities equivalent.

If class/object mechanics are the blocker, return to java-programming. This route is about architecture classification.