람다식&스트림

src/step05_lamda_and_stream/lamda/Calculable.java

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+package step05_lamda_and_stream.lamda;
+
+@FunctionalInterface
+public interface Calculable {
+    //추상메소드
+    void calculate(int x, int y);
+}

src/step05_lamda_and_stream/lamda/LamdaEx.java

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+package step05_lamda_and_stream.lamda;
+
+public class LamdaEx {
+    public static void main(String[] args) {
+        action((x,y) -> {
+            int result = x+y;
+            System.out.println("result: "+result);
+        });
+
+        action((x, y)-> {
+            int result = x - y;
+            System.out.println("result: "+result);
+        });
+    }
+
+    public static void action(Calculable calculable){
+        //데이터
+        int x = 10;
+        int y = 4;
+        //데이터 처리
+        calculable.calculate(x, y);
+    }
+}

src/step05_lamda_and_stream/stream/FilteringExample.java

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+package step05_lamda_and_stream.stream;
+
+import java.util.*;
+
+public class FilteringExample {
+    public static void main(String[] args) {
+        List<String> list = new ArrayList<>();
+        list.add("이규현");
+        list.add("이규현"); //중복
+        list.add("김규현2");
+        list.add("김규현3");
+        list.add("이규현4");
+
+        list.stream()
+                .distinct()
+                .forEach(name -> System.out.println(name));
+        System.out.println();
+
+        //김으로 시작하는 요소 필터링
+        list.stream()
+                .filter(name -> name.startsWith("김"))
+                .forEach(name -> System.out.println(name));
+        System.out.println();
+
+        //중복요소 먼저 제거 후 -> 필터링
+        list.stream()
+                .distinct()
+                .filter(name -> name.startsWith("김"))
+                .forEach(name -> System.out.println(name));
+    }
+}

src/step05_lamda_and_stream/stream/SortedExample.java

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+package step05_lamda_and_stream.stream;
+
+import java.util.*;
+public class SortedExample {
+    public static void main(String[] args) {
+        List<Student> studentList = new ArrayList<>();
+
+        studentList.add(new Student("이규현1", 100));
+        studentList.add(new Student("이규현2", 50));
+        studentList.add(new Student("이규현3", 80));
+
+        //오름차순
+        studentList.stream()
+                //231
+                .sorted((s1, s2) -> Integer.compare(s1.getScore(), s2.getScore()))
+                .forEach(student ->
+                        System.out.println("이름: "+student.getName()+",점수: "+student.getScore()));
+        System.out.println();
+
+        //내림차순
+        studentList.stream()
+                //132
+                .sorted((s1, s2) -> Integer.compare(s2.getScore(), s1.getScore()))
+                .forEach(student ->
+                        System.out.println("이름: "+student.getName()+",점수: "+student.getScore()));
+    }
+}

src/step05_lamda_and_stream/stream/StreamExample.java

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+package step05_lamda_and_stream.stream;
+
+import java.util.*;
+import java.util.stream.Stream;
+
+public class StreamExample {
+    public static void main(String[] args) {
+        //Set 컬렉션
+        Set<String> set = new HashSet<>();
+        set.add("이규현1");
+        set.add("이규현2");
+        set.add("이규현3");
+
+        //Stream으로 반복처리하기
+        Stream<String> stream = set.stream();
+        stream.forEach(name -> System.out.println(name));
+    }
+}

src/step05_lamda_and_stream/stream/Student.java

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+package step05_lamda_and_stream.stream;
+
+public class Student {
+    private String name;
+    private int score;
+
+    public Student(String name, int score){
+        this.name = name;
+        this.score = score;
+    }
+
+    public String getName(){return name;};
+    public int getScore(){return score;}
+}