design patterns : iterator

design-pattern/gof/src/iterator/after/Board.java

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+package iterator.after;
+
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+
+public class Board {
+
+    List<Post> posts = new ArrayList<>();
+
+    public List<Post> getPosts() {
+        return posts;
+    }
+
+    public void setPosts(List<Post> posts) {
+        this.posts = posts;
+    }
+
+    public void addPost(String content) {
+        this.posts.add(new Post(content));
+    }
+
+    public Iterator<Post> getDefaultIterator() {
+        return posts.iterator();
+    }
+
+    public Iterator<Post> getRecentPostIterator() {
+        return new RecentPostIterator(this.posts);
+    }
+}

design-pattern/gof/src/iterator/after/Client.java

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+package iterator.after;
+
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.List;
+
+public class Client {
+
+    public static void main(String[] args) {
+        Board board = new Board();
+        board.addPost("디자인 패턴 게임");
+        board.addPost("선생님, 저랑 디자인 패턴 하나 학습하시겠습니까?");
+        board.addPost("지금 이 자리에 계신 여러분들은 모두 디자인 패턴을 학습하고 계신 분들입니다.");
+
+        // TODO 들어간 순서대로 순회하기
+        List<Post> posts = board.getPosts();
+        Iterator<Post> iterator = board.getDefaultIterator();
+        while (iterator.hasNext()) {
+            System.out.println(iterator.next().getTitle());
+        }
+
+        // TODO 가장 최신 글 먼저 순회하기
+        Iterator<Post> recentPostIterator = board.getRecentPostIterator();
+        while (recentPostIterator.hasNext()) {
+            System.out.println(recentPostIterator.next().getTitle());
+        }
+
+    }
+
+}

design-pattern/gof/src/iterator/after/Post.java

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+package iterator.after;
+
+import java.time.LocalDateTime;
+
+public class Post {
+
+    private String title;
+
+    private LocalDateTime createdDateTime;
+
+    public Post(String title) {
+        this.title = title;
+        this.createdDateTime = LocalDateTime.now();
+    }
+
+    public String getTitle() {
+        return title;
+    }
+
+    public void setTitle(String title) {
+        this.title = title;
+    }
+
+    public LocalDateTime getCreatedDateTime() {
+        return createdDateTime;
+    }
+
+    public void setCreatedDateTime(LocalDateTime createdDateTime) {
+        this.createdDateTime = createdDateTime;
+    }
+}

design-pattern/gof/src/iterator/after/RecentPostIterator.java

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+package iterator.after;
+
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.List;
+
+public class RecentPostIterator implements Iterator<Post> {
+
+    private Iterator<Post> internalIterator;
+
+    public RecentPostIterator(List<Post> posts) {
+        Collections.sort(posts, (p1, p2) -> p2.getCreatedDateTime().compareTo(p1.getCreatedDateTime()));
+        this.internalIterator = posts.iterator();
+    }
+
+    @Override
+    public boolean hasNext() {
+        return this.internalIterator.hasNext();
+    }
+
+    @Override
+    public Post next() {
+        return this.internalIterator.next();
+    }
+}

design-pattern/gof/src/iterator/before/Board.java

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+package iterator.before;
+
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+
+public class Board {
+
+    List<Post> posts = new ArrayList<>();
+
+    public List<Post> getPosts() {
+        return posts;
+    }
+
+    public void setPosts(List<Post> posts) {
+        this.posts = posts;
+    }
+
+    public void addPost(String content) {
+        this.posts.add(new Post(content));
+    }
+}

design-pattern/gof/src/iterator/before/Client.java

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+package iterator.before;
+
+import java.util.Collections;
+import java.util.List;
+
+public class Client {
+
+    public static void main(String[] args) {
+        Board board = new Board();
+        board.addPost("디자인 패턴 게임");
+        board.addPost("선생님, 저랑 디자인 패턴 하나 학습하시겠습니까?");
+        board.addPost("지금 이 자리에 계신 여러분들은 모두 디자인 패턴을 학습하고 계신 분들입니다.");
+
+        // TODO 들어간 순서대로 순회하기
+        List<Post> posts = board.getPosts();
+        for (int i = 0 ; i < posts.size() ; i++) {
+            Post post = posts.get(i);
+            System.out.println(post.getTitle());
+        }
+
+        // TODO 가장 최신 글 먼저 순회하기
+        Collections.sort(posts, (p1, p2) -> p2.getCreatedDateTime().compareTo(p1.getCreatedDateTime()));
+        for (int i = 0 ; i < posts.size() ; i++) {
+            Post post = posts.get(i);
+            System.out.println(post.getTitle());
+        }
+    }
+
+}

design-pattern/gof/src/iterator/before/Post.java

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+package iterator.before;
+
+import java.time.LocalDateTime;
+
+public class Post {
+
+    private String title;
+
+    private LocalDateTime createdDateTime;
+
+    public Post(String title) {
+        this.title = title;
+        this.createdDateTime = LocalDateTime.now();
+    }
+
+    public String getTitle() {
+        return title;
+    }
+
+    public void setTitle(String title) {
+        this.title = title;
+    }
+
+    public LocalDateTime getCreatedDateTime() {
+        return createdDateTime;
+    }
+
+    public void setCreatedDateTime(LocalDateTime createdDateTime) {
+        this.createdDateTime = createdDateTime;
+    }
+}