[Ch15] Simplified the test harness for unpredictable run order

import java.util.concurrent.Executors;

public class UnpredictableRunOrder {

}

class RunWithThread {

  public static void main(String[] args) {

    for (int i = 0; i < 20; i++) {

      runThread();

    for (int i = 0; i < 100; i++) {

      ExecutorTestDrive.main(args);

    }

  }

}

  private static void runThread() {

class ThreadTestDrive {

  public static void main (String[] args) {

    Thread myThread = new Thread(() -> System.out.println("top o’ the stack"));

    myThread.start();

    System.out.println("back in main");

  }

}

class RunWithExecutor {

class ExecutorTestDrive {

  public static void main (String[] args) {

    ExecutorService executor = Executors.newSingleThreadExecutor();

    for (int i = 0; i < 100; i++) {

      executeRunnable(executor);

    }

    executor.shutdown();

  }

  private static void executeRunnable(ExecutorService executor) {

    executor.execute(() -> System.out.println("top o’ the stack"));

    System.out.println("back in main");

    executor.shutdown();

  }

}