code: /*
   * Copyright (c) 2016-present, RxJava Contributors.
   *
   * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in
   * compliance with the License. You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software distributed under the License is
   * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See
   * the License for the specific language governing permissions and limitations under the License.
   */
  
  package io.reactivex.rxjava3.internal.operators.observable;
  
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.atomic.AtomicReference;
  
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.disposables.Disposable;
  import io.reactivex.rxjava3.internal.disposables.*;
  
  public final class ObservableTimer extends Observable<Long> {
      final Scheduler scheduler;
      final long delay;
      final TimeUnit unit;
      public ObservableTimer(long delay, TimeUnit unit, Scheduler scheduler) {
          this.delay = delay;
          this.unit = unit;
          this.scheduler = scheduler;
      }
  
      @Override
      public void subscribeActual(Observer<? super Long> observer) {
          TimerObserver ios = new TimerObserver(observer);
          observer.onSubscribe(ios);
  
          Disposable d = scheduler.scheduleDirect(ios, delay, unit);
  
          ios.setResource(d);
      }
  
      static final class TimerObserver extends AtomicReference<Disposable>
      implements Disposable, Runnable {
  
          private static final long serialVersionUID = -2809475196591179431L;
  
          final Observer<? super Long> downstream;
  
          TimerObserver(Observer<? super Long> downstream) {
              this.downstream = downstream;
          }
  
          @Override
          public void dispose() {
              DisposableHelper.dispose(this);
          }
  
          @Override
          public boolean isDisposed() {
              return get() == DisposableHelper.DISPOSED;
          }
  
          @Override
          public void run() {
              if (!isDisposed()) {
                  downstream.onNext(0L);
                  lazySet(EmptyDisposable.INSTANCE);
                  downstream.onComplete();
              }
          }
  
          public void setResource(Disposable d) {
              DisposableHelper.trySet(this, d);
          }
      }
  }
  