Add demo code to assert that the throttleFirst does not switch thread.

app/build.gradle

@@ -26,8 +26,10 @@ android {
 dependencies {
     implementation fileTree(dir: 'libs', include: ['*.jar'])
     implementation 'com.jakewharton.rxrelay2:rxrelay:2.1.1'
-
+    implementation 'com.uber.autodispose:autodispose:1.4.0'
+    implementation 'com.uber.autodispose:autodispose-android-archcomponents:1.4.0'
     implementation 'io.reactivex.rxjava2:rxjava:2.2.21'
+    implementation 'io.reactivex.rxjava2:rxandroid:2.1.1'
     implementation 'androidx.appcompat:appcompat:1.3.1'
     implementation 'androidx.constraintlayout:constraintlayout:2.0.4'
     testImplementation 'junit:junit:4.13.2'

app/src/main/java/com/tonytang/hello/again/rxjava/MainActivity.java

@@ -1,13 +1,40 @@
 package com.tonytang.hello.again.rxjava;
 
-import androidx.appcompat.app.AppCompatActivity;
+import static com.uber.autodispose.AutoDispose.autoDisposable;
+import static com.uber.autodispose.android.lifecycle.AndroidLifecycleScopeProvider.from;
+
 import android.os.Bundle;
+import android.widget.TextView;
+import androidx.appcompat.app.AppCompatActivity;
+import io.reactivex.android.schedulers.AndroidSchedulers;
 
 public class MainActivity extends AppCompatActivity {
 
+  private TextView tv_throttle_first;
+  private TextView tv_throttle_last;
+
   @Override
   protected void onCreate(Bundle savedInstanceState) {
     super.onCreate(savedInstanceState);
     setContentView(R.layout.activity_main);
+    tv_throttle_first = findViewById(R.id.tv_throttle_first);
+    tv_throttle_last = findViewById(R.id.tv_throttle_last);
+    ThreadInfoStreaming.eventStreaming()
+        .observeOn(AndroidSchedulers.mainThread())
+        .as(autoDisposable(from(this)))
+        .subscribe(this::renderUI);
   }
+
+  private void renderUI(ThreadInfo threadInfo) {
+    switch (threadInfo.source) {
+      case THROTTLE_FIRST:
+        tv_throttle_first.setText(threadInfo.toString());
+        break;
+      case THROTTLE_LAST:
+        tv_throttle_last.setText(threadInfo.toString());
+        break;
+    }
+  }
+
+
 }

app/src/main/java/com/tonytang/hello/again/rxjava/Source.java

@@ -0,0 +1,6 @@
+package com.tonytang.hello.again.rxjava;
+
+public enum Source {
+  THROTTLE_FIRST,
+  THROTTLE_LAST
+}

app/src/main/java/com/tonytang/hello/again/rxjava/ThreadInfo.java

@@ -0,0 +1,23 @@
+package com.tonytang.hello.again.rxjava;
+
+import androidx.annotation.NonNull;
+import java.util.Locale;
+
+public class ThreadInfo {
+
+  public final long iteration;
+  public final Source source;
+  public final String threadName;
+
+  public ThreadInfo(long iteration, Source source, String threadName) {
+    this.iteration = iteration;
+    this.source = source;
+    this.threadName = threadName;
+  }
+
+  @NonNull
+  @Override
+  public String toString() {
+    return String.format(Locale.US, "%s:%s:%s", iteration, source, threadName);
+  }
+}

app/src/main/java/com/tonytang/hello/again/rxjava/ThreadInfoStreaming.java

@@ -0,0 +1,38 @@
+package com.tonytang.hello.again.rxjava;
+
+import io.reactivex.Observable;
+import io.reactivex.android.schedulers.AndroidSchedulers;
+import java.util.concurrent.TimeUnit;
+
+public class ThreadInfoStreaming {
+
+  private ThreadInfoStreaming() {
+  }
+
+  static Observable<ThreadInfo> eventStreaming() {
+    return Observable.merge(throttleFirst(), throttleLast());
+  }
+
+  private static Observable<ThreadInfo> throttleFirst() {
+    return rawStream()
+        .throttleFirst(1, TimeUnit.SECONDS)
+        .map(iteration -> new ThreadInfo(iteration, Source.THROTTLE_FIRST,
+            currentThreadName()));
+  }
+
+  private static Observable<ThreadInfo> throttleLast() {
+    return rawStream()
+        .throttleLast(1, TimeUnit.SECONDS)
+        .map(iteration -> new ThreadInfo(iteration, Source.THROTTLE_LAST,
+            currentThreadName()));
+  }
+
+  private static String currentThreadName() {
+    return Thread.currentThread().getName();
+  }
+
+  private static Observable<Long> rawStream() {
+    return Observable.interval(500, TimeUnit.MILLISECONDS)
+        .observeOn(AndroidSchedulers.mainThread());
+  }
+}

app/src/main/res/layout/activity_main.xml

@@ -1,21 +1,23 @@
 <?xml version="1.0" encoding="utf-8"?>
-<androidx.constraintlayout.widget.ConstraintLayout
-    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"
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+  xmlns:tools="http://schemas.android.com/tools"
+  android:layout_width="match_parent"
+  android:layout_height="match_parent"
+  android:orientation="vertical"
+  android:padding="16dp"
+  tools:context=".MainActivity">
+
+  <TextView
+    android:id="@+id/tv_throttle_first"
     android:layout_width="match_parent"
-    android:layout_height="match_parent"
-    tools:context=".MainActivity"
-    >
+    android:layout_height="wrap_content"
+     />
 
   <TextView
-      android:layout_width="wrap_content"
-      android:layout_height="wrap_content"
-      android:text="Hello World!"
-      app:layout_constraintBottom_toBottomOf="parent"
-      app:layout_constraintLeft_toLeftOf="parent"
-      app:layout_constraintRight_toRightOf="parent"
-      app:layout_constraintTop_toTopOf="parent"
+    android:id="@+id/tv_throttle_last"
+    android:layout_width="match_parent"
+    android:layout_marginTop="16dp"
+    android:layout_height="wrap_content"
       />
 
-</androidx.constraintlayout.widget.ConstraintLayout>
+</LinearLayout>

app/src/test/java/com/tonytang/hello/again/rxjava/ThrottleFirstTest.java

@@ -0,0 +1,21 @@
+package com.tonytang.hello.again.rxjava;
+
+import com.google.common.truth.Truth;
+import io.reactivex.Observable;
+import io.reactivex.observers.TestObserver;
+import io.reactivex.schedulers.Schedulers;
+import java.util.concurrent.TimeUnit;
+import org.junit.Test;
+
+public class ThrottleFirstTest {
+
+  @Test
+  public void without_cache_would_execute_footprint_three_times() {
+
+    TestObserver<Integer> test = Observable.just(1).throttleLatest(1, TimeUnit.SECONDS, Schedulers.computation()).test();
+    Thread thread = test.lastThread();
+    Truth.assertThat(thread.getName()).isEqualTo("Test worker");
+
+  }
+
+}