Virtual threads and ThreadLocal

vt-test.java

import lombok.SneakyThrows;
import lombok.extern.log4j.Log4j2;
import org.junit.jupiter.api.Test;

import java.util.concurrent.Executors;
import java.util.stream.IntStream;

@Log4j2
class TLTest {

    @Test
    @SneakyThrows
    void given_when_should() {
        int availableProcessors = Runtime.getRuntime()
                .availableProcessors();
        System.out.println("Detected CPU with " + availableProcessors + " logical threads.");

        try (var executor = Executors.newVirtualThreadPerTaskExecutor()) {
            IntStream.range(1, 50)
                    .mapToObj(this::createTask)
                    .forEach(task -> {
                        executor.submit(task);
                    });
        }
    }

    private Runnable createTask(int i) {
        return () -> {
            System.out.println("Start[" + i + "]: " + Thread.currentThread() + ": " + threadLocal.get());
            threadLocal.set("Task" + i);

            if (i % 2 == 0) {
                try {
                    // Simulate I/O blocking (e.g., reading a file)
                    Thread.sleep(1000);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }

            System.out.println("End[" + i + "]: " + Thread.currentThread() + ": " + threadLocal.get());
        };
    }

    private static final ThreadLocal<String> threadLocal = new ThreadLocal<>();

}