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线程1： exercises/threads/threads1.rs
题目
rust
// threads1.rs
//
// This program spawns multiple threads that each run for at least 250ms, and
// each thread returns how much time they took to complete. The program should
// wait until all the spawned threads have finished and should collect their
// return values into a vector.
//
// Execute `rustlings hint threads1` or use the `hint` watch subcommand for a
// hint.
// I AM NOT DONE
use std::thread;
use std::time::{Duration, Instant};
fn main() {
let mut handles = vec![];
for i in 0..10 {
handles.push(thread::spawn(move || {
let start = Instant::now();
thread::sleep(Duration::from_millis(250));
println!("thread {} is complete", i);
start.elapsed().as_millis()
}));
}
let mut results: Vec<u128> = vec![];
for handle in handles {
// TODO: a struct is returned from thread::spawn, can you use it?
}
if results.len() != 10 {
panic!("Oh no! All the spawned threads did not finish!");
}
println!();
for (i, result) in results.into_iter().enumerate() {
println!("thread {} took {}ms", i, result);
}
}这个程序生成了多个线程，每个线程运行至少250毫秒，并且每个线程都会返回它们运行的时间。程序应该等待，直到所有生成的线程都完成，并将他们的返回值收集到一个Vec中。
题目解析
JoinHandle是一个从生成的线程中返回的结构体。我们可以通过join()等待线程结束，然后从结果中获取到各个线程的执行时间。
rust
use std::thread;
use std::time::{Duration, Instant};
fn main() {
let mut handles = vec![];
for i in 0..10 {
handles.push(thread::spawn(move || {
let start = Instant::now();
thread::sleep(Duration::from_millis(250));
println!("thread {} is complete", i);
start.elapsed().as_millis()
}));
}
let mut results: Vec<u128> = vec![];
for handle in handles {
// TODO: a struct is returned from thread::spawn, can you use it?
results.push(handle.join().unwrap())
}
if results.len() != 10 {
panic!("Oh no! All the spawned threads did not finish!");
}
println!();
for (i, result) in results.into_iter().enumerate() {
println!("thread {} took {}ms", i, result);
}
}