Concurrency
并发
What you’ll learn: How Rust concurrency compares to Java threads, executors, and synchronized shared state.
本章将学习： Rust 并发模型如何对应 Java 线程、执行器以及同步共享状态。Difficulty: 🔴 Advanced
难度： 🔴 高级
Java gives teams mature concurrency tools. Rust brings a different advantage: the compiler participates more directly in preventing misuse.
Java 已经给团队提供了非常成熟的并发工具，而 Rust 的优势则落在另一边：编译器会更直接地参与阻止误用。
Core Mapping
核心映射
| Java | Rust |
|---|---|
Thread | std::thread::spawn |
ExecutorService | async runtime or manual thread orchestration 异步运行时或手工线程编排 |
| synchronized mutable state 同步共享可变状态 | Mutex<T> |
| concurrent shared ownership 并发共享所有权 | Arc<T> |
| queues and handoff 队列与交接 | channels |
Shared State
共享状态
#![allow(unused)]
fn main() {
use std::sync::{Arc, Mutex};
use std::thread;
let counter = Arc::new(Mutex::new(0));
}Rust makes the ownership and synchronization cost explicit in the type spelling.
Rust 会把所有权和同步成本直接写在类型上，不让它们偷偷躲起来。
Send and Sync
Send 与 Sync
These marker traits are part of what makes Rust concurrency feel stricter:
Rust 并发之所以显得更严，Send 和 Sync 是关键原因之一：
Send: a value can move across threads
值可以跨线程移动。Sync: references to a value can be shared across threads safely
值的引用可以安全地跨线程共享。
Java developers rarely think at this level because the JVM and library conventions hide it.
Java 开发者很少在这个层面思考问题，因为 JVM 和库约定通常把这层细节藏起来了。
Advice
建议
- prefer message passing when shared mutable state is not necessary
只要能避免共享可变状态，就优先消息传递。 - when shared state is necessary, make the synchronization type explicit
共享状态躲不过去时，就把同步类型老老实实写出来。 - let the compiler teach where thread-safety assumptions break
让编译器来指出线程安全假设在哪些地方站不住。
Rust does not make concurrency easy by hiding the problem. It makes it safer by forcing the important parts into the type system.
Rust 不是靠把并发问题藏起来来显得简单，而是靠把关键约束推进类型系统里来变得更安全。