#36 rxjava: method reference

RxJava/practice/src/main/java/org/example/ex07/CarInventory.java

@@ -0,0 +1,14 @@
+package org.example.ex07;
+
+public class CarInventory {
+    private int incomingCount;
+    private int totalCount;
+
+    public CarInventory(int totalCount) {
+        this.totalCount = totalCount;
+    }
+
+    public int getExpectedTotalCount(int incomingCount){
+        return totalCount + incomingCount;
+    }
+}

RxJava/practice/src/main/java/org/example/ex07/ClassNameInstanceMethodEx.java

@@ -0,0 +1,18 @@
+package org.example.ex07;
+
+import java.util.function.Function;
+
+/**
+ * Class Name::instance method 메서드 레퍼런스 예
+ */
+public class ClassNameInstanceMethodEx {
+    public static void main(String[] args) {
+        Function<Car, String> f1 = car -> car.getCarName();
+        String carName1 = f1.apply(new Car("트래버스"));
+        System.out.println(carName1);
+
+        Function<Car, String> f2 = Car::getCarName;
+        String carName2 = f2.apply(new Car("팰리세이드"));
+        System.out.println(carName2);
+    }
+}

RxJava/practice/src/main/java/org/example/ex07/ClassNameStaticMethodEx.java

@@ -0,0 +1,26 @@
+package org.example.ex07;
+
+import java.util.function.Function;
+
+/**
+ * Class Name::static method 메서드 레퍼런스 예
+ */
+public class ClassNameStaticMethodEx {
+    public static void main(String[] args) {
+        // 람다 표현식 메서드 레퍼런스로 축약 전
+        Function<String, Integer> f1 = (String s) -> Integer.parseInt(s);
+        Integer result1 = f1.apply("3");
+        System.out.println(result1);
+
+        // 람다 표현식 메서드 레퍼런스로 축약 전
+        Function<String, Integer> f2 = s -> Integer.parseInt(s);
+        Integer result2 = f2.apply("3");
+        System.out.println(result2);
+
+        // 람다 표현식을 메서드 레퍼런스로 축약
+        Function<String, Integer> f3 = Integer::parseInt;
+        Integer result3 = f3.apply("3");
+        System.out.println(result3);
+
+    }
+}

RxJava/practice/src/main/java/org/example/ex07/ConstructorReferenceEx.java

@@ -0,0 +1,20 @@
+package org.example.ex07;
+
+import org.example.common.Car;
+
+import java.util.function.Function;
+
+/**
+ * Constructor::new 예
+ */
+public class ConstructorReferenceEx {
+    public static void main(String[] args) {
+        Function<String, Car> f1 = s -> new Car(s);
+        Car car1 = f1.apply("콜로라도");
+        System.out.println(car1.getCarName());
+
+        Function<String, Car> f2 = Car::new;
+        Car car2 = f2.apply("카니발");
+        System.out.println(car2.getCarName());
+    }
+}

RxJava/practice/src/main/java/org/example/ex07/ObjectInstanceMethodExample.java

@@ -0,0 +1,32 @@
+package org.example.ex07;
+
+import java.util.function.Function;
+import java.util.function.IntUnaryOperator;
+import java.util.function.UnaryOperator;
+
+/**
+ * Object::instance method 예
+ */
+public class ObjectInstanceMethodExample {
+    public static void main(String[] args) {
+        final CarInventory carInventory = new CarInventory(10);
+
+        Function<Integer, Integer> f1 = count -> carInventory.getExpectedTotalCount(count);
+        int totalCount1 = f1.apply(10);
+        System.out.println(totalCount1);
+
+        Function<Integer, Integer> f2 = carInventory::getExpectedTotalCount;
+        int totalCount2 = f2.apply(20);
+        System.out.println(totalCount2);
+
+        // T -> T
+        UnaryOperator<Integer> f3 = carInventory::getExpectedTotalCount;
+        int totalCount3 = f3.apply(30);
+        System.out.println(totalCount3);
+
+        // Integer -> Integer
+        IntUnaryOperator f4 = carInventory::getExpectedTotalCount;
+        int totalCount4 = f4.applyAsInt(40);
+        System.out.println(totalCount4);
+    }
+}