[jhlee] mission 1 - 자바8 스트림, 람다, Optional

src/main/java/nextstep/fp/Conditional.java

@@ -0,0 +1,5 @@
+package nextstep.fp;
+
+public interface Conditional {
+    public boolean isTrue(int number);
+}

src/main/java/nextstep/fp/Lambda.java

@@ -2,6 +2,7 @@
 
 import java.util.List;
 
+
 public class Lambda {
     public static void printAllOld(List<Integer> numbers) {
         System.out.println("printAllOld");
@@ -26,31 +27,21 @@ public void run() {
         }).start();
     }
 
-    public static int sumAll(List<Integer> numbers) {
+    public static int sumAll(List<Integer> numbers, Conditional condition) {
         int total = 0;
         for (int number : numbers) {
-            total += number;
+            if (condition.isTrue(number)) {
+                total += number;
+            }
         }
         return total;
     }
 
     public static int sumAllEven(List<Integer> numbers) {
-        int total = 0;
-        for (int number : numbers) {
-            if (number % 2 == 0) {
-                total += number;
-            }
-        }
-        return total;
+        return sumAll(numbers, number -> (number % 2) == 0);
     }
 
     public static int sumAllOverThree(List<Integer> numbers) {
-        int total = 0;
-        for (int number : numbers) {
-            if (number > 3) {
-                total += number;
-            }
-        }
-        return total;
+        return sumAll(numbers, number -> number > 3);
     }
 }

src/main/java/nextstep/fp/StreamStudy.java

@@ -5,6 +5,7 @@
 import java.nio.file.Files;
 import java.nio.file.Paths;
 import java.util.Arrays;
+import java.util.Comparator;
 import java.util.List;
 import java.util.stream.Collectors;
 
@@ -27,7 +28,13 @@ public static void printLongestWordTop100() throws IOException {
                 .get("src/main/resources/fp/war-and-peace.txt")), StandardCharsets.UTF_8);
         List<String> words = Arrays.asList(contents.split("[\\P{L}]+"));
 
-        // TODO 이 부분에 구현한다.
+        words.stream()
+                .filter(w -> w.length() > 12)
+                .sorted(Comparator.comparingInt(String::length).reversed())
+                .distinct()
+                .limit(100)
+                .forEach(x -> System.out.println(x.toUpperCase()));
+
     }
 
     public static List<Integer> doubleNumbers(List<Integer> numbers) {
@@ -39,6 +46,9 @@ public static long sumAll(List<Integer> numbers) {
     }
 
     public static long sumOverThreeAndDouble(List<Integer> numbers) {
-        return 0;
+        return numbers.stream()
+                .filter(x -> x > 3)
+                .map(x -> x * 2)
+                .reduce(0, (x, y) -> x + y);
     }
 }

src/main/java/nextstep/optional/Expression.java

@@ -1,5 +1,7 @@
 package nextstep.optional;
 
+import java.util.Arrays;
+
 enum Expression {
     PLUS("+"), MINUS("-"), TIMES("*"), DIVIDE("/");
 
@@ -14,12 +16,9 @@ private static boolean matchExpression(Expression e, String expression) {
     }
 
     static Expression of(String expression) {
-        for (Expression v : values()) {
-            if (matchExpression(v, expression)) {
-                return v;
-            }
-        }
-
-        throw new IllegalArgumentException(String.format("%s는 사칙연산에 해당하지 않는 표현식입니다.", expression));
+        return Arrays.stream(values())
+                .filter(v -> matchExpression(v, expression))
+                .findFirst()
+                .orElseThrow(() -> new IllegalArgumentException(String.format("%s는 사칙연산에 해당하지 않는 표현식입니다.", expression)));
     }
 }

src/main/java/nextstep/optional/User.java

@@ -1,6 +1,9 @@
 package nextstep.optional;
 
+import java.util.Optional;
+
 public class User {
+
     private String name;
     private Integer age;
 
@@ -33,7 +36,13 @@ public static boolean ageIsInRange1(User user) {
     }
 
     public static boolean ageIsInRange2(User user) {
-        return false;
+        Optional<User> optionalUser = Optional.ofNullable(user);
+
+        return optionalUser.filter(u -> (
+                        u.getAge() != null) &&
+                        u.getAge() >= 30 && u.getAge() <= 45
+                ).isPresent();
+
     }
 
     @Override
@@ -47,23 +56,30 @@ public int hashCode() {
 
     @Override
     public boolean equals(Object obj) {
-        if (this == obj)
+        if (this == obj) {
             return true;
-        if (obj == null)
+        }
+        if (obj == null) {
             return false;
-        if (getClass() != obj.getClass())
+        }
+        if (getClass() != obj.getClass()) {
             return false;
+        }
         User other = (User) obj;
         if (age == null) {
-            if (other.age != null)
+            if (other.age != null) {
                 return false;
-        } else if (!age.equals(other.age))
+            }
+        } else if (!age.equals(other.age)) {
             return false;
+        }
         if (name == null) {
-            if (other.name != null)
+            if (other.name != null) {
                 return false;
-        } else if (!name.equals(other.name))
+            }
+        } else if (!name.equals(other.name)) {
             return false;
+        }
         return true;
     }
 }

src/main/java/nextstep/optional/Users.java

@@ -2,6 +2,7 @@
 
 import java.util.Arrays;
 import java.util.List;
+import java.util.Optional;
 
 public class Users {
     static final User DEFAULT_USER = new User("codesquad", 100);
@@ -13,11 +14,11 @@ public class Users {
             new User("honux", 45));
 
     User getUser(String name) {
-        for (User user : users) {
-            if (user.matchName(name)) {
-                return user;
-            }
-        }
-        return DEFAULT_USER;
+
+        return users.stream()
+                .filter(user -> user.matchName(name))
+                .findFirst()
+                .orElse(DEFAULT_USER);
+
     }
 }

src/test/java/nextstep/fp/CarTest.java

@@ -8,24 +8,14 @@ public class CarTest {
     @Test
     public void 이동() {
         Car car = new Car("pobi", 0);
-        Car actual = car.move(new MoveStrategy() {
-            @Override
-            public boolean isMovable() {
-                return true;
-            }
-        });
+        Car actual = car.move(() -> true);
         assertThat(actual).isEqualTo(new Car("pobi", 1));
     }
 
     @Test
     public void 정지() {
         Car car = new Car("pobi", 0);
-        Car actual = car.move(new MoveStrategy() {
-            @Override
-            public boolean isMovable() {
-                return false;
-            }
-        });
+        Car actual = car.move(() -> false);
         assertThat(actual).isEqualTo(new Car("pobi", 0));
     }
 }

src/test/java/nextstep/fp/LambdaTest.java

@@ -33,7 +33,7 @@ public void runThread() throws Exception {
 
     @Test
     public void sumAll() throws Exception {
-        int sum = Lambda.sumAll(numbers);
+        int sum = Lambda.sumAll(numbers, number -> true);
         assertThat(sum).isEqualTo(21);
     }