Copy cat > /tmp/AdvLab02.java << 'JAVAEOF'
import java.util.concurrent.*;
import java.util.*;
import java.util.stream.*;
import java.util.concurrent.atomic.*;
public class AdvLab02 {
record Product(int id, String name, double price) {}
record PriceQuote(int productId, String source, double price) {}
static double fetchPrice(int id, String source, double base) {
try { Thread.sleep(50 + (id * 10)); } catch (InterruptedException e) { Thread.currentThread().interrupt(); }
return Math.round(base * (0.9 + id * 0.01) * 100) / 100.0;
}
public static void main(String[] args) throws Exception {
var products = List.of(
new Product(1, "Surface Pro", 864.0),
new Product(2, "Surface Pen", 49.99),
new Product(3, "Office 365", 99.99),
new Product(4, "USB-C Hub", 29.99),
new Product(5, "Surface Book", 1299.0));
// Step 1: 1000 virtual tasks
System.out.println("=== Virtual Threads (Java 21) ===");
int N = 1000;
var latch = new CountDownLatch(N);
var counter = new AtomicInteger(0);
long t0 = System.currentTimeMillis();
try (var executor = Executors.newVirtualThreadPerTaskExecutor()) {
for (int i = 0; i < N; i++) {
executor.submit(() -> {
try { Thread.sleep(10); } catch (InterruptedException e) {}
counter.incrementAndGet();
latch.countDown();
});
}
}
latch.await(10, TimeUnit.SECONDS);
System.out.printf(" %d virtual tasks completed in %dms%n", counter.get(), System.currentTimeMillis()-t0);
System.out.println(" (same work on platform threads: ~1000 OS threads or async callbacks)");
// Step 2: Parallel price fetch — I/O bound
System.out.println("\n=== Parallel Price Fetch ===");
t0 = System.currentTimeMillis();
var futures = new ArrayList<Future<PriceQuote>>();
try (var vexec = Executors.newVirtualThreadPerTaskExecutor()) {
for (var p : products) {
for (var source : List.of("US", "EU", "APAC")) {
futures.add(vexec.submit(() -> new PriceQuote(p.id(), source, fetchPrice(p.id(), source, p.price()))));
}
}
}
var quotes = futures.stream().map(f -> { try { return f.get(); } catch (Exception e) { throw new RuntimeException(e); } }).toList();
long elapsed = System.currentTimeMillis() - t0;
System.out.printf(" Fetched %d quotes in %dms (sequential ~%dms)%n", quotes.size(), elapsed, quotes.size() * 60L);
var bestPrices = quotes.stream().collect(Collectors.groupingBy(PriceQuote::productId,
Collectors.minBy(Comparator.comparingDouble(PriceQuote::price))));
bestPrices.entrySet().stream().sorted(Map.Entry.comparingByKey())
.forEach(e -> e.getValue().ifPresent(q ->
System.out.printf(" Product %-2d best: %-4s $%.2f%n", e.getKey(), q.source(), q.price())));
// Step 3: Thread.ofVirtual() API
System.out.println("\n=== Thread.ofVirtual() API ===");
var results = new ConcurrentLinkedQueue<String>();
var threads = new ArrayList<Thread>();
for (int i = 0; i < 5; i++) {
final int id = i;
threads.add(Thread.ofVirtual().name("vt-" + id).start(() -> {
try { Thread.sleep(10); } catch (InterruptedException e) {}
results.add("vt-" + id + " isVirtual=" + Thread.currentThread().isVirtual());
}));
}
for (var t : threads) t.join();
results.stream().sorted().forEach(r -> System.out.println(" " + r));
// Step 4: Virtual vs Platform properties
System.out.println("\n=== Virtual vs Platform Thread ===");
var vt = Thread.ofVirtual().start(() -> {});
vt.join();
System.out.println(" Virtual: isVirtual=" + vt.isVirtual() + " isDaemon=" + vt.isDaemon());
var pt = Thread.ofPlatform().start(() -> {});
pt.join();
System.out.println(" Platform: isVirtual=" + pt.isVirtual() + " isDaemon=" + pt.isDaemon());
// Step 5: ReentrantLock (not synchronized) to avoid pinning
System.out.println("\n=== ReentrantLock (Avoids Pinning) ===");
var lock = new java.util.concurrent.locks.ReentrantLock();
var lockResults = new ConcurrentLinkedQueue<Integer>();
try (var vexec = Executors.newVirtualThreadPerTaskExecutor()) {
var fs = new ArrayList<Future<?>>();
for (int i = 0; i < 10; i++) {
final int n = i;
fs.add(vexec.submit(() -> {
lock.lock();
try { Thread.sleep(5); lockResults.add(n); }
catch (InterruptedException e) {}
finally { lock.unlock(); }
}));
}
for (var f : fs) f.get();
}
System.out.println(" 10 tasks with ReentrantLock: " + lockResults.stream().sorted().toList());
}
}
JAVAEOF
docker run --rm -v /tmp/AdvLab02.java:/tmp/AdvLab02.java zchencow/innozverse-java:latest sh -c "javac /tmp/AdvLab02.java -d /tmp && java -cp /tmp AdvLab02" 