Rust for Java Programmers

Crates and Modules

What you’ll learn: How Rust code organization maps to Java packages, modules, and artifacts.

Difficulty: 🟢 Beginner

Rust organizes code around crates and modules rather than packages and classpaths.

Mental Mapping

Basic Layout

src/
├── main.rs
├── lib.rs
├── api.rs
└── model/
    └── user.rs

Visibility

• items are private by default
• pub exposes an item more broadly
• pub(crate) exposes within the current crate

This default privacy is stricter than typical Java codebases and often leads to cleaner boundaries.

Guidance

• keep module trees shallow at first
• design crate boundaries around ownership of concepts, not around arbitrary layering
• expose a small public API and keep the rest internal

Crates and modules are simpler than many Java build layouts, but they reward deliberate boundary design.