diff --git a/RxJava/practice/src/main/java/org/example/common/SampleData.java b/RxJava/practice/src/main/java/org/example/common/SampleData.java
index 77f7a878..4c82aa19 100644
--- a/RxJava/practice/src/main/java/org/example/common/SampleData.java
+++ b/RxJava/practice/src/main/java/org/example/common/SampleData.java
@@ -1,5 +1,7 @@
 package org.example.common;
 
+import io.reactivex.rxjava3.core.Observable;
+
 import java.util.Arrays;
 import java.util.List;
 import java.util.concurrent.TimeUnit;
diff --git a/RxJava/practice/src/main/java/org/example/ex06/FunctionalInterfaceEx.java b/RxJava/practice/src/main/java/org/example/ex06/FunctionalInterfaceEx.java
new file mode 100644
index 00000000..75fb0f26
--- /dev/null
+++ b/RxJava/practice/src/main/java/org/example/ex06/FunctionalInterfaceEx.java
@@ -0,0 +1,40 @@
+package org.example.ex06;
+
+import org.example.common.*;
+
+import java.util.Arrays;
+import java.util.List;
+
+/**
+ * 사용자 정의 Predicate를 익명 클래스로 구현하는 예제
+ */
+public class FunctionalInterfaceEx {
+    public static void main(String[] args) {
+        List<Car> cars = Arrays.asList(
+                new Car(CarMaker.HYUNDAE, CarType.SUV, "팰리세이드", 28000000, true),
+                new Car(CarMaker.SAMSUNG, CarType.SEDAN, "SM5", 35000000, true),
+                new Car(CarMaker.CHEVROLET, CarType.SUV, "트래버스", 50000000, true),
+                new Car(CarMaker.KIA, CarType.SEDAN, "K5", 20000000, false),
+                new Car(CarMaker.SSANGYOUNG, CarType.SUV, "티볼리", 23000000, true)
+        );
+
+        List<Car> carsFilteredByPrice = CarFilter.filterCarByCustomPredicate(cars, new CarPredicate() {
+            @Override
+            public boolean test(Car car) {
+                return car.getCarPrice() > 30000000;
+            }
+        });
+
+        for(Car car : carsFilteredByPrice)
+            System.out.println("차 이름: " + car.getCarName() + ", 가격: " + car.getCarPrice());
+
+        List<Car> carsFilteredByCarType = CarFilter.filterCarByCustomPredicate(cars, new CarPredicate() {
+            @Override
+            public boolean test(Car car) {
+                return car.getCarType().equals(CarType.SUV);
+            }
+        });
+        for(Car car : carsFilteredByCarType)
+            System.out.println("차 이름: " + car.getCarName() + ", 차종: " + car.getCarType());
+    }
+}
\ No newline at end of file
diff --git a/RxJava/practice/src/main/java/org/example/ex06/FunctionalInterfaceToLamdaEx.java b/RxJava/practice/src/main/java/org/example/ex06/FunctionalInterfaceToLamdaEx.java
new file mode 100644
index 00000000..11b06864
--- /dev/null
+++ b/RxJava/practice/src/main/java/org/example/ex06/FunctionalInterfaceToLamdaEx.java
@@ -0,0 +1,34 @@
+package org.example.ex06;
+
+import org.example.common.Car;
+import org.example.common.CarFilter;
+import org.example.common.CarMaker;
+import org.example.common.CarType;
+
+import java.util.Arrays;
+import java.util.List;
+
+/**
+ * 사용자 정의 Predicate를 람다 표현식으로 사용하는 예제
+ */
+public class FunctionalInterfaceToLamdaEx {
+    public static void main(String[] args) {
+        List<Car> cars = Arrays.asList(
+                new Car(CarMaker.HYUNDAE, CarType.SUV, "팰리세이드", 28000000, true),
+                new Car(CarMaker.SAMSUNG, CarType.SEDAN, "SM5", 35000000, true),
+                new Car(CarMaker.CHEVROLET, CarType.SUV, "트래버스", 50000000, true),
+                new Car(CarMaker.KIA, CarType.SEDAN, "K5", 20000000, false),
+                new Car(CarMaker.SSANGYOUNG, CarType.SUV, "티볼리", 23000000, true)
+        );
+
+        List<Car> carsFilteredByPrice =
+                CarFilter.filterCarByCustomPredicate(cars, (Car car) -> car.getCarPrice() > 30000000);
+        for(Car car : carsFilteredByPrice)
+            System.out.println("차 이름: " + car.getCarName() + ", 가격: " + car.getCarPrice());
+
+        List<Car> carsFilteredByCarType =
+                CarFilter.filterCarByCustomPredicate(cars, car -> car.getCarType().equals(CarType.SUV));
+        for(Car car : carsFilteredByCarType)
+            System.out.println("차 이름: " + car.getCarName() + ", 차종: " + car.getCarType());
+    }
+}
\ No newline at end of file
diff --git a/RxJava/practice/src/main/java/org/example/ex06/LegacyInterfaceEx.java b/RxJava/practice/src/main/java/org/example/ex06/LegacyInterfaceEx.java
new file mode 100644
index 00000000..c93e42e3
--- /dev/null
+++ b/RxJava/practice/src/main/java/org/example/ex06/LegacyInterfaceEx.java
@@ -0,0 +1,35 @@
+package org.example.ex06;
+
+import org.example.common.Car;
+import org.example.common.CarMaker;
+import org.example.common.CarType;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.List;
+
+/**
+ * 하나의 추상 메서드를 가지고 있는 기존 인터페이스를 구현하는 예제
+ */
+public class LegacyInterfaceEx {
+    public static void main(String[] args) {
+        List<Car> cars = Arrays.asList(
+                new Car(CarMaker.HYUNDAE, CarType.SUV, "팰리세이드", 28000000, true),
+                new Car(CarMaker.SAMSUNG, CarType.SEDAN, "SM5", 35000000, true),
+                new Car(CarMaker.CHEVROLET, CarType.SUV, "트래버스", 50000000, true),
+                new Car(CarMaker.KIA, CarType.SEDAN, "K5", 20000000, false),
+                new Car(CarMaker.SSANGYOUNG, CarType.SUV, "티볼리", 23000000, true)
+        );
+
+        Collections.sort(cars, new Comparator<Car>() {
+            @Override
+            public int compare(Car car1, Car car2) {
+                return car1.getCarPrice() - car2.getCarPrice();
+            }
+        });
+
+        for(Car car : cars)
+            System.out.println("차 이름: " + car.getCarName() + ", 가격: " + car.getCarPrice());
+    }
+}
\ No newline at end of file
diff --git a/RxJava/practice/src/main/java/org/example/ex06/LegacyInterfaceToFunctionalInterfaceEx.java b/RxJava/practice/src/main/java/org/example/ex06/LegacyInterfaceToFunctionalInterfaceEx.java
new file mode 100644
index 00000000..b6a619b4
--- /dev/null
+++ b/RxJava/practice/src/main/java/org/example/ex06/LegacyInterfaceToFunctionalInterfaceEx.java
@@ -0,0 +1,30 @@
+package org.example.ex06;
+
+import org.example.common.Car;
+import org.example.common.CarMaker;
+import org.example.common.CarType;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
+/**
+ * 하나의 추상 메서드를 가지고 있는 기존 인터페이스를 함수형 인터페이스로 사용하는 예제
+ */
+public class LegacyInterfaceToFunctionalInterfaceEx {
+    public static void main(String[] args) {
+
+        List<Car> cars = Arrays.asList(
+                new Car(CarMaker.HYUNDAE, CarType.SUV, "팰리세이드", 28000000, true),
+                new Car(CarMaker.SAMSUNG, CarType.SEDAN, "SM5", 35000000, true),
+                new Car(CarMaker.CHEVROLET, CarType.SUV, "트래버스", 50000000, true),
+                new Car(CarMaker.KIA, CarType.SEDAN, "K5", 20000000, false),
+                new Car(CarMaker.SSANGYOUNG, CarType.SUV, "티볼리", 23000000, true)
+        );
+
+        Collections.sort(cars, (car1, car2) -> car1.getCarPrice() - car2.getCarPrice());
+
+        for(Car car : cars)
+            System.out.println("차 이름: " + car.getCarName() + ", 가격: " + car.getCarPrice());
+    }
+}
\ No newline at end of file