# Threads & Runnable — Advanced Java

Source: https://www.geekswithgeeks.com/en/advanced-java/adv-threads

> Start threads with Runnable and start(), wait with join(), and see how Java 21 virtual threads make blocking code scale to millions of tasks.

## Create and start

Pass a `Runnable` to a `Thread` and call `start()` (not `run()`, which would execute on the current thread). `join()` waits for it to finish. Prefer an executor over managing raw threads.

```java
Thread t = new Thread(() -> {
    System.out.println("worker: " + Thread.currentThread().getName());
});
t.start();
t.join();
```

## Virtual threads

Java 21 adds **virtual threads** — cheap, JVM-scheduled threads you can create by the million. Blocking IO on a virtual thread parks it without pinning an OS thread, so straightforward blocking code scales.