Example of using a Mutex to share data between threads

example_multithread.rs

#![allow(unused)]

use std::{collections::HashMap, sync::{Arc, Mutex}};
use rand::Rng;


#[derive(Debug)]
struct UserData {
    name: String,
    age: u32,
}
impl UserData {
    fn new(name: String, age: u32) -> UserData {
        UserData { name, age }
    }
}

const FIRST_NAMES: &[&str] = &["Alex", "Olivia", "Liam", "Sophia", "Noah", "Emma", "Ethan", "Ava", "Caden", "Mia"];

fn get_random_firstname() -> &'static str {
    let index = rand::rng().random_range(1..FIRST_NAMES.len());
    FIRST_NAMES[index]
}

/// Example of using a Mutex to share data between threads
/// The data is a HashMap with an integer key and a UserData value
/// Each thread will insert a new UserData into the HashMap
/// The main thread will wait for all threads to finish and then print the HashMap
fn main() {

    let data : Arc<Mutex<HashMap<i32,UserData>>>= Arc::new(Mutex::new(HashMap::new()));
    println!("Memory usage of data: {:?}", std::mem::size_of_val(&data));
    let mut threads: HashMap<i32, std::thread::JoinHandle<()>> = HashMap::new();

    for i in 0..10 {
        // Clone the data to move it into the thread
        let data = data.clone();
        let thread = std::thread::spawn(move || {
            println!("#{} Thread starting...", i);
            // Sleep between 10 and 5000 ms
            std::thread::sleep(std::time::Duration::from_millis(rand::rng().random_range(10..5000)));
            let age = rand::rng().random_range(20..80);
            let firstname=  get_random_firstname().to_string();
            let user = UserData::new(firstname.to_string(), age);
            println!("#{} Data generated, waiting lock...", i);
            data.lock().unwrap().insert(i, user);
            println!("#{} Thread ended.", i);
        });
        threads.insert(i, thread);
    }
    println!("All threads created");

    // Wait for all threads to finish
    for (i, thread) in threads {
        thread.join().unwrap();
    }

    let data = data.lock().unwrap();
    assert_eq!(data.len(), 10);
    println!("User data: {:?}", data);

}