带你快速搞定java多线程(2)

package thread;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
/**
* @author 香菜
*/
public class FutureTest {
private ExecutorService bossExecutor = Executors.newSingleThreadExecutor();
public Future<Integer> getHpTask(Integer input) {
return bossExecutor.submit(() -> {
System.out.println("Calculating..." + input);
Thread.sleep(1000);
return input * input;
});
}
public static void main(String[] args) throws ExecutionException, InterruptedException {
Future<Integer> calculate = new FutureTest().getHpTask(100);
System.out.println(calculate.get());
System.out.println("Done");
}
}

public V get() throws InterruptedException, ExecutionException {
      int s = state;
      if (s <= COMPLETING)
          s = awaitDone(false, 0L);
      return report(s);
  }
  private int awaitDone(boolean timed, long nanos)
      throws InterruptedException {
      final long deadline = timed ? System.nanoTime() + nanos : 0L;
      WaitNode q = null;
      boolean queued = false;
      for (;;) {
          if (Thread.interrupted()) {
              removeWaiter(q);
              throw new InterruptedException();
          }
          int s = state;
          if (s > COMPLETING) {
              if (q != null)
                  q.thread = null;
              return s;
          }
          else if (s == COMPLETING) // cannot time out yet
              Thread.yield();
          else if (q == null)
              q = new WaitNode();
          else if (!queued)
              queued = UNSAFE.compareAndSwapObject(this, waitersOffset,
                                                    q.next = waiters, q);
          else if (timed) {
              nanos = deadline - System.nanoTime();
              if (nanos <= 0L) {
                  removeWaiter(q);
                  return state;
              }
              LockSupport.parkNanos(this, nanos);
          }
          else
              LockSupport.park(this);
      }
  }