rustHow to use a Rust HashMap in a multithreaded environment?

Rust HashMap can be used in a multithreaded environment by using the Arc type. Arc stands for atomic reference count and is a type of pointer that allows multiple threads to access the same data. An example of using Arc with a HashMap is shown below:

use std::sync::Arc;
use std::collections::HashMap;

let map: HashMap<i32, i32> = HashMap::new();
let arc_map = Arc::new(map);

// Spawn threads
for i in 0..10 {
    let arc_map = arc_map.clone();
    thread::spawn(move || {
        // Access the map here
        let mut map = arc_map.lock().unwrap();
        map.insert(i, i * 2);
    });
}

The code above creates a HashMap and wraps it in an Arc type. It then spawns 10 threads which access the map and insert a key-value pair.

Parts of the code:

• Arc::new(map): Creates an Arc type from the map HashMap.
• arc_map.clone(): Clones the Arc type so that each thread can access it.
• arc_map.lock().unwrap(): Locks the Arc type so that only one thread can access it at a time.
• map.insert(i, i * 2): Inserts a key-value pair into the map.

Helpful links

• Rust Docs - Arc
• Rust Docs - HashMap

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