RxJava - Completable Observable

The Completable class represents deferred response. Completable observable can either indicate a successful completion or error.

Class Declaration

Following is the declaration for io.reactivex.rxjava3.core.Completable<T> class −

public abstract class Completable
   extends Object
      implements CompletableSource

Protocol

Following is the sequential protocol that Single Observable operates −

onSubscribe (onError | OnComplete)?

Example - Creating a Completable Observable Class to get Data

ObservableTester.java

package com.tutorialspoint;

import io.reactivex.rxjava3.core.Completable;

public class ObservableTester {
   public static void main(String[] args) throws InterruptedException {
      Completable.complete().doOnComplete(() -> System.out.println("Hello World")).subscribe();
   }
}

Output

Compile and Run the code to verify the following output −

Hello World

Example - Usage of Completable Observable Class to get Data after a delay of 2 seconds

ObservableTester.java

package com.tutorialspoint;

import java.util.concurrent.TimeUnit;

import io.reactivex.rxjava3.core.Completable;
import io.reactivex.rxjava3.disposables.Disposable;
import io.reactivex.rxjava3.observers.DisposableCompletableObserver;
import io.reactivex.rxjava3.schedulers.Schedulers;


public class ObservableTester {
   public static void main(String[] args) throws InterruptedException {

      //Create an observer
      Disposable disposable = Completable.complete()
         .delay(2, TimeUnit.SECONDS, Schedulers.io())
         .subscribeWith(new DisposableCompletableObserver() {
         @Override
         public void onError(Throwable e) { 
            e.printStackTrace();
         }
         @Override
         public void onStart() {
            System.out.println("Started!");
         }
         @Override
         public void onComplete() {
            System.out.println("Done!");
         }
      }); 
      Thread.sleep(3000);
      //start observing
      disposable.dispose();
   }
}

Output

Compile and Run the code to verify the following output −

Started!
Done!