build.gradle

    // To make API calls
    def retrofitVersion = '2.6.0'

    // To logs API calls & responses
    def logging_version = '4.0.0'
		
    // To use Rx to handle the response and observe the changes in realtime
    def rxandroid_version = '2.1.1'
    def rxjava_version = '2.1.1'
    def rxcalladapter_version = '2.6.0'
    def reactivestreams_version = "1.1.1"

    // Retrofit
    implementation "com.squareup.retrofit2:retrofit:$retrofitVersion"
    implementation "com.squareup.retrofit2:converter-gson:$retrofitVersion"

    // Http logging
    implementation "com.squareup.okhttp3:logging-interceptor:$logging_version"

    // Rx-Retrofit Call Adapter
    implementation "com.squareup.retrofit2:adapter-rxjava2:$rxcalladapter_version"
		
    // RxAndroid
    implementation "io.reactivex.rxjava2:rxandroid:$rxandroid_version"

    // RxJava
    implementation "io.reactivex.rxjava2:rxjava:$rxjava_version"
		
    // Reactive Streams (convert Observable to LiveData)
    implementation "android.arch.lifecycle:reactivestreams:$reactivestreams_version"