From 81e90a39f8f3e548f58eac43c3d011b7f0d54cdc Mon Sep 17 00:00:00 2001
From: haerong22 <haerong22@naver.com>
Date: Wed, 16 Mar 2022 17:10:30 +0900
Subject: [PATCH] rxjava : stream

---
 RxJava/basic/src/_03_stream/StreamEx_06.java | 16 +++++++++
 RxJava/basic/src/_03_stream/StreamEx_07.java | 18 ++++++++++
 RxJava/basic/src/_03_stream/StreamEx_08.java | 17 ++++++++++
 RxJava/basic/src/_03_stream/StreamEx_09.java | 29 ++++++++++++++++
 RxJava/basic/src/_03_stream/StreamEx_10.java | 35 ++++++++++++++++++++
 RxJava/basic/src/_03_stream/StreamEx_11.java | 28 ++++++++++++++++
 6 files changed, 143 insertions(+)
 create mode 100644 RxJava/basic/src/_03_stream/StreamEx_06.java
 create mode 100644 RxJava/basic/src/_03_stream/StreamEx_07.java
 create mode 100644 RxJava/basic/src/_03_stream/StreamEx_08.java
 create mode 100644 RxJava/basic/src/_03_stream/StreamEx_09.java
 create mode 100644 RxJava/basic/src/_03_stream/StreamEx_10.java
 create mode 100644 RxJava/basic/src/_03_stream/StreamEx_11.java

diff --git a/RxJava/basic/src/_03_stream/StreamEx_06.java b/RxJava/basic/src/_03_stream/StreamEx_06.java
new file mode 100644
index 00000000..1dc3f855
--- /dev/null
+++ b/RxJava/basic/src/_03_stream/StreamEx_06.java
@@ -0,0 +1,16 @@
+package _03_stream;
+
+import java.util.List;
+
+public class StreamEx_06 {
+
+    public static void main(String[] args) {
+
+        List<Dish> vegetarianMenu = Dish.menu.stream()
+                .filter(Dish::isVegetarian)
+                .toList();
+
+        System.out.println("vegetarianMenu = " + vegetarianMenu);
+
+    }
+}
diff --git a/RxJava/basic/src/_03_stream/StreamEx_07.java b/RxJava/basic/src/_03_stream/StreamEx_07.java
new file mode 100644
index 00000000..ac857cb0
--- /dev/null
+++ b/RxJava/basic/src/_03_stream/StreamEx_07.java
@@ -0,0 +1,18 @@
+package _03_stream;
+
+import java.util.Arrays;
+import java.util.List;
+
+public class StreamEx_07 {
+
+    public static void main(String[] args) {
+
+        // distinct -> hashCode, equals 로 결정
+        List<Integer> list = Arrays.asList(1, 2, 1, 3, 3, 2, 4);
+
+        list.stream()
+                .filter(i -> i % 2 == 0)
+                .distinct()
+                .forEach(System.out::println);
+    }
+}
diff --git a/RxJava/basic/src/_03_stream/StreamEx_08.java b/RxJava/basic/src/_03_stream/StreamEx_08.java
new file mode 100644
index 00000000..7616c3a5
--- /dev/null
+++ b/RxJava/basic/src/_03_stream/StreamEx_08.java
@@ -0,0 +1,17 @@
+package _03_stream;
+
+import java.util.List;
+
+public class StreamEx_08 {
+
+    public static void main(String[] args) {
+
+        // skip(n) n번째 요소 이후의 요소만 선택, 없으면 빈배열
+        List<Dish> dishes = Dish.menu.stream()
+                .filter(dish -> dish.getCalories() > 300)
+                .skip(2)
+                .toList();
+
+        System.out.println("dishes = " + dishes);
+    }
+}
diff --git a/RxJava/basic/src/_03_stream/StreamEx_09.java b/RxJava/basic/src/_03_stream/StreamEx_09.java
new file mode 100644
index 00000000..58140a0f
--- /dev/null
+++ b/RxJava/basic/src/_03_stream/StreamEx_09.java
@@ -0,0 +1,29 @@
+package _03_stream;
+
+import java.util.Arrays;
+import java.util.List;
+
+public class StreamEx_09 {
+
+    public static void main(String[] args) {
+
+        // map -> 다른 타입으로 변환
+        List<Integer> result = Dish.menu.stream()
+                .map(Dish::getName)// Dish -> String
+                .map(String::length)// String -> Integer
+                .toList();
+
+        System.out.println("result = " + result);
+
+        // flatMap
+        List<String> words = Arrays.asList("Hello", "world");
+
+        List<String> uniqueCharacter = words.stream()
+                .map(word -> word.split("")) // String -> String[] 이 되므로 Stream<String[]>
+                .flatMap(Arrays::stream) // Stream<String>
+                .distinct()
+                .toList();
+
+        System.out.println("uniqueCharacter = " + uniqueCharacter);
+    }
+}
diff --git a/RxJava/basic/src/_03_stream/StreamEx_10.java b/RxJava/basic/src/_03_stream/StreamEx_10.java
new file mode 100644
index 00000000..e6b805b2
--- /dev/null
+++ b/RxJava/basic/src/_03_stream/StreamEx_10.java
@@ -0,0 +1,35 @@
+package _03_stream;
+
+import java.util.Optional;
+
+public class StreamEx_10 {
+
+    public static void main(String[] args) {
+        if (isVegetarianFriendlyMenu()) {
+            System.out.println("Vegetarian friendly");
+        }
+
+        System.out.println(isHealthyMenu());
+        System.out.println(isHealthyMenu2());
+
+        findVegetarianDish()
+                .ifPresent(dish -> System.out.println(dish.getName()));
+    }
+
+    private static Optional<Dish> findVegetarianDish() {
+        return Dish.menu.stream().filter(Dish::isVegetarian).findAny();
+    }
+
+    private static boolean isHealthyMenu2() {
+        return Dish.menu.stream().noneMatch(dish -> dish.getCalories() >= 1000);
+    }
+
+    private static boolean isHealthyMenu() {
+        return Dish.menu.stream().allMatch(dish -> dish.getCalories() < 1000);
+    }
+
+    private static boolean isVegetarianFriendlyMenu() {
+        return Dish.menu.stream().anyMatch(Dish::isVegetarian);
+    }
+
+}
diff --git a/RxJava/basic/src/_03_stream/StreamEx_11.java b/RxJava/basic/src/_03_stream/StreamEx_11.java
new file mode 100644
index 00000000..71006d17
--- /dev/null
+++ b/RxJava/basic/src/_03_stream/StreamEx_11.java
@@ -0,0 +1,28 @@
+package _03_stream;
+
+import java.util.Arrays;
+import java.util.List;
+
+public class StreamEx_11 {
+
+    public static void main(String[] args) {
+
+        List<Integer> numbers = Arrays.asList(3, 4, 5, 1, 2);
+
+        Integer sum = numbers.stream().reduce(0, Integer::sum);
+        System.out.println("sum = " + sum);
+
+        numbers.stream().reduce(Math::min)
+                .ifPresent(System.out::println);
+
+        numbers.stream().reduce(Math::max)
+                .ifPresent(System.out::println);
+
+        List<String> strings = Arrays.asList("a", "b", "c");
+
+        strings.stream()
+                .filter(str -> !str.equals("b"))
+                .reduce((a, b) -> a + b)
+                .ifPresent(System.out::println);
+    }
+}