Java Solar System (Swing)

Simple Java desktop simulation of the solar system with elliptical orbits, labels, controls, and a lightweight 3D-like projection.

Tech Stack

• Java 25 by default (Gradle toolchain, override with -PjavaVersion=21 if needed)
• Swing/AWT for UI and rendering
• Gradle (with wrapper)
• Jackson (JSON loading for planet data)
• JUnit 5 for unit tests

Project Layout

• src/main/java/com/raph/solarsystem/ - app entry point and UI wiring
• src/main/java/com/raph/solarsystem/model/ - domain model + physics + JSON loader
• src/main/java/com/raph/solarsystem/controller/ - simulation state/control logic
• src/main/java/com/raph/solarsystem/view/ - renderer + controls panel
• src/main/resources/planets.json - planet dataset
• src/test/java/com/raph/solarsystem/ - unit tests
• docs/PLANET.md - data documentation
• docs/PHYSICS.md - formulas and motion model
• docs/ORBIT_ENGINE.md - formula-to-code mapping

Run

./gradlew run

If Java 25 is not installed locally, use:

./gradlew -PjavaVersion=21 run

Test

./gradlew test

Runtime Controls

• Speed slider and presets (1x, 10x, 100x)
• Pause/Resume, Reset
• 3D tilt toggle + strength slider
• Hover info toggle
• FPS slider + presets (20, 30, 60)
• Performance mode (reduced render cost)
• Zoom slider + Fit
• Mouse wheel zoom
• Keyboard zoom: +, -, 0 (fit)
• Language selector: English / French / Japanese

Quick Math Glossary

• a (semiMajorAu): semi-major axis, orbit size (in AU).
• e (eccentricity): orbit shape (0 circular, closer to 1 more elongated).
• P (periodDays): time for one full orbit (days).
• n (mean motion): average angular speed, n = 2π / P.
• M (mean anomaly): time-based orbital phase angle.
• E (eccentric anomaly): intermediate angle solving Kepler equation.
• ν (true anomaly): actual geometric angle of the planet from perihelion.
• Perihelion: closest distance to Sun, a(1 - e).
• Aphelion: farthest distance from Sun, a(1 + e).

For details and formulas, see docs/PHYSICS.md and docs/ORBIT_ENGINE.md.

Design Pattern (High-Level)

• Model-Controller-View split:
  • Model: planet data and orbital calculations
  • Controller: mutable simulation settings and time progression
  • View: rendering and UI controls

Architecture Flow

flowchart LR
    A[ControlsPanel<br/>UI events] --> B[SolarSystemController<br/>state + simulation flags]
    B --> C[SolarSystemModel<br/>time + planets]
    C --> D[SolarSystemRenderer<br/>draw orbits/planets/HUD]
    D --> E[SolarPanel - Swing<br/>paintComponent]
    F[planets.json] --> C

Loading

Quick read:

• ControlsPanel updates controller settings (speed, fps, tilt, zoom, etc.)
• SolarPanel timer ticks call controller/model progression
• SolarSystemRenderer reads model + render context and draws the frame
• planets.json is the source of orbital/display data