build.gradle

allprojects {
    repositories {
        maven { url "https://oss.jfrog.org/libs-snapshot" }
    }
}

dependencies {
    implementation 'io.reactivex.rxjava3:rxandroid:3.0.0'
    implementation 'io.reactivex.rxjava3:rxjava:3.0.0'
}

defaultConfig {
        applicationId "com.app.app"
        minSdkVersion 19
        targetSdkVersion 30
        versionCode 1
        versionName "1.0"
        compileOptions {
            sourceCompatibility JavaVersion.VERSION_1_8
            targetCompatibility JavaVersion.VERSION_1_8
        }
        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }

RxDelay.java

 Observable.just(obj)
                .delay(500, TimeUnit.MILLISECONDS)
                .subscribe(obj -> {
                    //do something
                });

RxDelay1.java

                  Observable.empty()
                        .delay(3, TimeUnit.SECONDS)
                        .subscribe(new Observer<Object>() {
                            @Override
                            public void onSubscribe(@NonNull Disposable d) {

                            }

                            @Override
                            public void onNext(@NonNull Object o) {

                            }

                            @Override
                            public void onError(@NonNull Throwable e) {

                            }

                            @Override
                            public void onComplete() {
                                
                            }
                        });