3주차 - Step1 리뷰 요청 드립니다. (#149)

* [step1] docs : 수업내용 저장

* [step1] feat : Lambda 실습

* [step1] feat : Stream 실습

* [step1] feat : Optional 실습

Author: Integerous

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

@@ -0,0 +1,6 @@
+package nextstep.fp;
+
+@FunctionalInterface
+public interface Conditional {
+    boolean test(int number);
+}

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

@@ -18,39 +18,24 @@ public static void printAllLambda(List<Integer> numbers) {
 	}
 
 	public static void runThread() {
-		new Thread(new Runnable() {
-		    @Override
-		    public void run() {
-		        System.out.println("Hello from thread");
-		    }
-		}).start();
+        new Thread(() -> System.out.println("Hello from thread")).start();
+	}
+
+	public static int sum(List<Integer> numbers, Conditional condition) {
+        return numbers.stream()
+                .filter(condition::test)
+                .reduce(0, Integer::sum);
 	}
 
 	public static int sumAll(List<Integer> numbers) {
-	    int total = 0;
-	    for (int number : numbers) {
-	        total += number;
-	    }
-	    return total;
+		return sum(numbers, number -> true);
 	}
-	
+
 	public static int sumAllEven(List<Integer> numbers) {
-	    int total = 0;
-	    for (int number : numbers) {
-	        if (number % 2 == 0) {
-	            total += number;
-	        }
-	    }
-	    return total;
+		return sum(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 sum(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;
 
@@ -22,12 +23,18 @@ public static long countWords() throws IOException {
 		return count;
 	}
 
-	public static void printLongestWordTop100() throws IOException {
+	public static List<String> printLongestWordTop100() throws IOException {
 		String contents = new String(Files.readAllBytes(Paths
 				.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.
+
+        return words.stream()
+                .filter(word -> word.length() > 12)
+                .distinct()
+                .limit(100)
+                .sorted(Comparator.comparing(String::length).reversed())
+                .map(String::toLowerCase)
+                .collect(Collectors.toList());
 	}
 
 	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(number -> number > 3)
+                .map(number -> 2 * number)
+                .reduce(0, Integer::sum);
 	}
 }

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(Expression.values())
+                .filter(value -> matchExpression(value, expression))
+                .findFirst()
+                .orElseThrow(() -> new IllegalArgumentException(String.format("%s는 사칙연산에 해당하지 않는 표현식입니다.", expression)));
 	}
 }

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

@@ -1,5 +1,9 @@
 package nextstep.optional;
 
+import jdk.nashorn.internal.runtime.options.Option;
+
+import java.util.Optional;
+
 public class User {
     private String name;
     private Integer age;
@@ -33,7 +37,10 @@ public static boolean ageIsInRange1(User user) {
     }
 
     public static boolean ageIsInRange2(User user) {
-        return false;
+        return Optional.ofNullable(user)
+                .map(User::getAge)
+                .filter(age -> age >= 30 && age <= 45)
+                .isPresent();
     }
 
     @Override

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

@@ -13,11 +13,9 @@ 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

@@ -5,27 +5,29 @@
 import static org.assertj.core.api.Assertions.assertThat;
 
 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;
+//            }
+//        });
+//        assertThat(actual).isEqualTo(new Car("pobi", 1));
+//    }
+
     @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/StreamStudyTest.java

@@ -24,7 +24,7 @@ public void countWords() throws Exception {
 
 	@Test
 	public void printLongestWordTop100() throws Exception {
-		StreamStudy.printLongestWordTop100();
+	    StreamStudy.printLongestWordTop100().forEach(System.out::println);
 	}
 
 	@Test