Add structured concurrency example for prime generation (classless,

instance-main, IO.println)

src/pp.09.02-StructuredConcurrency/src/main/java/pp/structuredPrime.java

@@ -0,0 +1,14 @@
+import java.util.concurrent.StructuredTaskScope.Joiner;
+
+BigInteger parallelPrime(int bitLength) throws InterruptedException {
+    try (var scope = StructuredTaskScope.open(Joiner.<BigInteger>anySuccessfulResultOrThrow())) {
+        for (var i = 0; i < ForkJoinPool.commonPool().getParallelism(); i++) {
+            scope.fork(() -> BigInteger.probablePrime(bitLength, ThreadLocalRandom.current()));
+        }
+        return scope.join();
+    }
+}
+
+void main() throws InterruptedException {
+    IO.println(parallelPrime(4096));
+}