diff --git a/RxJava/practice/src/main/java/org/example/ex01/DeclarativePrograming.java b/RxJava/practice/src/main/java/org/example/ex01/DeclarativePrograming.java
new file mode 100644
index 00000000..aa1d9665
--- /dev/null
+++ b/RxJava/practice/src/main/java/org/example/ex01/DeclarativePrograming.java
@@ -0,0 +1,19 @@
+package org.example.ex01;
+
+import java.util.Arrays;
+import java.util.List;
+
+public class DeclarativePrograming {
+
+    public static void main(String[] args){
+        // List에 있는 숫자들 중에서 6보다 큰 홀수들의 합계를 구하세요.
+        List<Integer> numbers = Arrays.asList(1, 3, 21, 10, 8, 11);
+
+        int sum = numbers.stream()
+                .filter(number -> number > 6 && (number % 2 != 0))
+                .mapToInt(number -> number)
+                .sum();
+
+        System.out.println("# 선언형 프로그래밍 사용: " + sum);
+    }
+}
\ No newline at end of file
diff --git a/RxJava/practice/src/main/java/org/example/ex01/ImperativeProgramming.java b/RxJava/practice/src/main/java/org/example/ex01/ImperativeProgramming.java
new file mode 100644
index 00000000..f3758657
--- /dev/null
+++ b/RxJava/practice/src/main/java/org/example/ex01/ImperativeProgramming.java
@@ -0,0 +1,21 @@
+package org.example.ex01;
+
+import java.util.Arrays;
+import java.util.List;
+
+public class ImperativeProgramming {
+
+    public static void main(String[] args){
+        // List에 있는 숫자들 중에서 6보다 큰 홀수들의 합계를 구하세요.
+        List<Integer> numbers = Arrays.asList(1, 3, 21, 10, 8, 11);
+        int sum = 0;
+
+        for(int number : numbers){
+             if(number > 6 && (number % 2 != 0)){
+                 sum += number;
+             }
+        }
+
+        System.out.println("# 명령형 프로그래밍 사용: " + sum);
+    }
+}
\ No newline at end of file
diff --git a/RxJava/practice/src/main/java/org/example/ex01/ReactiveProgramming.java b/RxJava/practice/src/main/java/org/example/ex01/ReactiveProgramming.java
new file mode 100644
index 00000000..2d6baae3
--- /dev/null
+++ b/RxJava/practice/src/main/java/org/example/ex01/ReactiveProgramming.java
@@ -0,0 +1,18 @@
+package org.example.ex01;
+
+import io.reactivex.rxjava3.core.Observable;
+import io.reactivex.rxjava3.schedulers.Schedulers;
+
+public class ReactiveProgramming {
+
+    public static void main(String[] args) throws InterruptedException {
+        Observable.just(100, 200, 300, 400, 500)
+                .doOnNext(data -> System.out.println(Thread.currentThread().getName() + " : #doOnNext() : " +  data))
+                .subscribeOn(Schedulers.io())
+                .observeOn(Schedulers.computation())
+                .filter(number -> number > 300)
+                .subscribe(num -> System.out.println(Thread.currentThread().getName() + " : result : " + num));
+
+        Thread.sleep(500);
+    }
+}