java8 : stream api

java8to11/src/stream/App.java

@@ -1,8 +1,11 @@
 package stream;
 
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.List;
+import java.util.function.Predicate;
 import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
 /**
  * 스트림은 데이터를 담고 있는 저장소(컬렉션)이 아니다.
@@ -13,18 +16,79 @@ import java.util.stream.Collectors;
 
 public class App {
     public static void main(String[] args) {
-        List<String> names = new ArrayList<>();
-        names.add("kim");
-        names.add("lee");
-        names.add("park");
-        names.add("choi");
+        List<OnlineClass> springClasses = new ArrayList<>();
+        springClasses.add(new OnlineClass(1, "spring boot", true));
+        springClasses.add(new OnlineClass(2, "spring data jpa", true));
+        springClasses.add(new OnlineClass(3, "spring mvc", false));
+        springClasses.add(new OnlineClass(4, "spring core", false));
+        springClasses.add(new OnlineClass(5, "rest api development", false));
 
-        // 쉬운 병렬처리
-        List<String> collect = names.parallelStream().map(s -> {
-            System.out.println(s + " " + Thread.currentThread().getName());
-            return s.toUpperCase();
-        }).collect(Collectors.toList());
-        collect.forEach(System.out::println);
+        System.out.println("spring 으로 시작하는 수업");
+        springClasses.stream()
+                .filter(c -> c.getTitle().startsWith("spring"))
+                .forEach(c -> System.out.println(c.getTitle()));
+        System.out.println("===============================================");
+
+        System.out.println("close 되지 않은 수업");
+        springClasses.stream()
+                .filter(Predicate.not(OnlineClass::isClosed))
+                .forEach(c -> System.out.println(c.getTitle()));
+        System.out.println("===============================================");
+
+        System.out.println("수업 이름만 모아서 스트림 만들기");
+        springClasses.stream()
+                .map(OnlineClass::getTitle)
+                .forEach(System.out::println);
+
+        List<OnlineClass> javaClasses = new ArrayList<>();
+        javaClasses.add(new OnlineClass(6, "The Java, Test", true));
+        javaClasses.add(new OnlineClass(7, "The Java, Code manipulation", true));
+        javaClasses.add(new OnlineClass(8, "The Java, 8 to 11", false));
+
+        List<List<OnlineClass>> events = new ArrayList<>();
+        events.add(springClasses);
+        events.add(javaClasses);
+
+        System.out.println("두 수업 목록에 들어있는 모든 수업 아이디 출력");
+        events.stream()
+                .flatMap(Collection::stream)
+                .forEach(c -> System.out.println(c.getId()));
+        System.out.println("===============================================");
+
+        System.out.println("10부터 1씩 증가하는 무제한 스트림 중에서 앞에 10개 빼고 최대 10개 까지만");
+        Stream.iterate(10, i -> i + 1)
+                .skip(10)
+                .limit(10)
+                .forEach(System.out::println);
+        System.out.println("===============================================");
+
+        System.out.println("자바 수업 중에 Test가 들어있는 수업이 있는지 확인");
+        boolean test = javaClasses.stream()
+                .anyMatch(oc -> oc.getTitle().contains("Test"));
+        System.out.println(test);
+        System.out.println("===============================================");
+
+        System.out.println("스프링 수업 중에 제목이 spring 이 들어간 제목만 모아서 List 로 만들기");
+        List<String> spring = springClasses.stream()
+                .map(OnlineClass::getTitle)
+                .filter(title -> title.contains("spring"))
+                .collect(Collectors.toList());
+        spring.forEach(System.out::println);
+        System.out.println("===============================================");
+
+
+//        List<String> names = new ArrayList<>();
+//        names.add("kim");
+//        names.add("lee");
+//        names.add("park");
+//        names.add("choi");
+//
+//        // 쉬운 병렬처리
+//        List<String> collect = names.parallelStream().map(s -> {
+//            System.out.println(s + " " + Thread.currentThread().getName());
+//            return s.toUpperCase();
+//        }).collect(Collectors.toList());
+//        collect.forEach(System.out::println);
 
 //        // 중계형 오퍼레이터는 Lazy -> 종료형 오퍼레이터가 오기 전까지 실행 X
 //        names.stream().map((s) -> {

java8to11/src/stream/OnlineClass.java

@@ -0,0 +1,37 @@
+package stream;
+
+public class OnlineClass {
+    private Integer id;
+    private String title;
+    private boolean closed;
+
+    public OnlineClass(Integer id, String title, boolean closed) {
+        this.id = id;
+        this.title = title;
+        this.closed = closed;
+    }
+
+    public Integer getId() {
+        return id;
+    }
+
+    public void setId(Integer id) {
+        this.id = id;
+    }
+
+    public String getTitle() {
+        return title;
+    }
+
+    public void setTitle(String title) {
+        this.title = title;
+    }
+
+    public boolean isClosed() {
+        return closed;
+    }
+
+    public void setClosed(boolean closed) {
+        this.closed = closed;
+    }
+}