diff --git a/RxJava/practice/src/main/java/org/example/ex04/HelloRxJavaFlowableCreateEx.java b/RxJava/practice/src/main/java/org/example/ex04/HelloRxJavaFlowableCreateEx.java
new file mode 100644
index 00000000..1263f6a6
--- /dev/null
+++ b/RxJava/practice/src/main/java/org/example/ex04/HelloRxJavaFlowableCreateEx.java
@@ -0,0 +1,63 @@
+package org.example.ex04;
+
+import io.reactivex.rxjava3.core.BackpressureStrategy;
+import io.reactivex.rxjava3.core.Flowable;
+import io.reactivex.rxjava3.core.FlowableEmitter;
+import io.reactivex.rxjava3.core.FlowableOnSubscribe;
+import io.reactivex.rxjava3.schedulers.Schedulers;
+import org.example.utils.LogType;
+import org.example.utils.Logger;
+import org.reactivestreams.Subscriber;
+import org.reactivestreams.Subscription;
+
+public class HelloRxJavaFlowableCreateEx {
+    public static void main(String[] args) throws InterruptedException {
+        Flowable<String> flowable =
+                Flowable.create(new FlowableOnSubscribe<String>() {
+                    @Override
+                    public void subscribe(FlowableEmitter<String> emitter) throws Exception {
+                        String[] datas = {"Hello", "RxJava!"};
+                        for(String data : datas) {
+                            // 구독이 해지되면 처리 중단
+                            if (emitter.isCancelled())
+                                return;
+
+                            // 데이터 통지
+                            emitter.onNext(data);
+                        }
+
+                        // 데이터 통지 완료를 알린다
+                        emitter.onComplete();
+                    }
+                }, BackpressureStrategy.BUFFER); // 구독자의 처리가 늦을 경우 데이터를 버퍼에 담아두는 설정.
+
+        flowable.observeOn(Schedulers.computation())
+                .subscribe(new Subscriber<String>() {
+                    // 데이터 개수 요청 및 구독을 취소하기 위한 Subscription 객체
+                    private Subscription subscription;
+
+                    @Override
+                    public void onSubscribe(Subscription subscription) {
+                            this.subscription = subscription;
+                            this.subscription.request(Long.MAX_VALUE);
+                    }
+
+                    @Override
+                    public void onNext(String data) {
+                        Logger.log(LogType.ON_NEXT, data);
+                    }
+
+                    @Override
+                    public void onError(Throwable error) {
+                        Logger.log(LogType.ON_ERROR, error);
+                    }
+
+                    @Override
+                    public void onComplete() {
+                        Logger.log(LogType.ON_COMPLETE);
+                    }
+                });
+
+        Thread.sleep(500L);
+    }
+}
\ No newline at end of file
diff --git a/RxJava/practice/src/main/java/org/example/ex04/HelloRxJavaFlowableCreateLambdaEx.java b/RxJava/practice/src/main/java/org/example/ex04/HelloRxJavaFlowableCreateLambdaEx.java
new file mode 100644
index 00000000..8ca14eac
--- /dev/null
+++ b/RxJava/practice/src/main/java/org/example/ex04/HelloRxJavaFlowableCreateLambdaEx.java
@@ -0,0 +1,38 @@
+package org.example.ex04;
+
+import io.reactivex.rxjava3.core.BackpressureStrategy;
+import io.reactivex.rxjava3.core.Flowable;
+import io.reactivex.rxjava3.schedulers.Schedulers;
+import org.example.utils.LogType;
+import org.example.utils.Logger;
+import org.reactivestreams.Subscriber;
+import org.reactivestreams.Subscription;
+
+public class HelloRxJavaFlowableCreateLambdaEx {
+    public static void main(String[] args) throws InterruptedException {
+        Flowable<String> flowable =
+                Flowable.create(emitter -> {
+                    String[] datas = {"Hello", "RxJava!"};
+                    for(String data : datas) {
+                        // 구독이 해지되면 처리 중단
+                        if (emitter.isCancelled())
+                            return;
+
+                        // 데이터 발행
+                        emitter.onNext(data);
+                    }
+
+                    // 데이터 발행 완료를 알린다
+                    emitter.onComplete();
+                }, BackpressureStrategy.BUFFER);
+
+        flowable.observeOn(Schedulers.computation())
+                .subscribe(
+                        data -> Logger.log(LogType.ON_NEXT, data),
+                        error -> Logger.log(LogType.ON_ERROR, error),
+                        () -> Logger.log(LogType.ON_COMPLETE)
+                );
+
+        Thread.sleep(500L);
+    }
+}
\ No newline at end of file
diff --git a/RxJava/practice/src/main/java/org/example/ex04/HelloRxJavaObservableCreateEx.java b/RxJava/practice/src/main/java/org/example/ex04/HelloRxJavaObservableCreateEx.java
new file mode 100644
index 00000000..8f385783
--- /dev/null
+++ b/RxJava/practice/src/main/java/org/example/ex04/HelloRxJavaObservableCreateEx.java
@@ -0,0 +1,54 @@
+package org.example.ex04;
+
+import io.reactivex.rxjava3.core.Observable;
+import io.reactivex.rxjava3.core.ObservableEmitter;
+import io.reactivex.rxjava3.core.ObservableOnSubscribe;
+import io.reactivex.rxjava3.core.Observer;
+import io.reactivex.rxjava3.disposables.Disposable;
+import io.reactivex.rxjava3.schedulers.Schedulers;
+import org.example.utils.LogType;
+import org.example.utils.Logger;
+
+public class HelloRxJavaObservableCreateEx {
+    public static void main(String[] args) throws InterruptedException {
+        Observable<String> observable =
+                Observable.create(new ObservableOnSubscribe<String>() {
+                    @Override
+                    public void subscribe(ObservableEmitter<String> emitter) throws Exception {
+                        String[] datas = {"Hello", "RxJava!"};
+                        for (String data : datas) {
+                            if (emitter.isDisposed())
+                                return;
+
+                            emitter.onNext(data);
+                        }
+                        emitter.onComplete();
+                    }
+                });
+
+        observable.observeOn(Schedulers.computation())
+                .subscribe(new Observer<>() {
+                    @Override
+                    public void onSubscribe(Disposable disposable) {
+                        // 아무 처리도 하지 않음.
+                    }
+
+                    @Override
+                    public void onNext(String data) {
+                        Logger.log(LogType.ON_NEXT, data);
+                    }
+
+                    @Override
+                    public void onError(Throwable error) {
+                        Logger.log(LogType.ON_ERROR, error);
+                    }
+
+                    @Override
+                    public void onComplete() {
+                        Logger.log(LogType.ON_COMPLETE);
+                    }
+                });
+
+        Thread.sleep(500L);
+    }
+}
\ No newline at end of file
diff --git a/RxJava/practice/src/main/java/org/example/ex04/HelloRxJavaObservableCreateLambdaEx.java b/RxJava/practice/src/main/java/org/example/ex04/HelloRxJavaObservableCreateLambdaEx.java
new file mode 100644
index 00000000..d84ebaa1
--- /dev/null
+++ b/RxJava/practice/src/main/java/org/example/ex04/HelloRxJavaObservableCreateLambdaEx.java
@@ -0,0 +1,33 @@
+package org.example.ex04;
+
+import io.reactivex.rxjava3.core.Observable;
+import io.reactivex.rxjava3.core.Observer;
+import io.reactivex.rxjava3.disposables.Disposable;
+import io.reactivex.rxjava3.schedulers.Schedulers;
+import org.example.utils.LogType;
+import org.example.utils.Logger;
+
+public class HelloRxJavaObservableCreateLambdaEx {
+    public static void main(String[] args) throws InterruptedException {
+        Observable<String> observable =
+                Observable.create(emitter -> {
+                    String[] datas = {"Hello", "RxJava!"};
+                    for (String data : datas) {
+                        if (emitter.isDisposed())
+                            return;
+
+                        emitter.onNext(data);
+                    }
+                    emitter.onComplete();
+                });
+
+        observable.observeOn(Schedulers.computation())
+                .subscribe(
+                        data -> Logger.log(LogType.ON_NEXT, data),
+                        error -> Logger.log(LogType.ON_NEXT, error),
+                        () -> Logger.log(LogType.DO_ON_COMPLETE)
+                );
+
+        Thread.sleep(500L);
+    }
+}
\ No newline at end of file