<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="org.ntlab.developrx.JavaMainActivity">

    <android.support.constraint.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <Button
            android:id="@+id/flowable_btn"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="flowable (Reactive Streams)"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent" />

        <Button
            android:id="@+id/observable_btn"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="observable"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toBottomOf="@id/flowable_btn" />
    </android.support.constraint.ConstraintLayout>

</ScrollView>