ueb07 a)

ueb07_news_example/src/client/Client.java

@@ -1,8 +1,6 @@
 package client;
 
-import model.Article;
-import model.Image;
-import model.NewsCollection;
+import model.*;
 
 public class Client {
 	
@@ -20,9 +18,13 @@ public class Client {
 				.addItem(new Image("Missing cat", 1280, 720, "anonymous")));
 
 		System.out.println("\n===List===\n");
-		System.out.print(masterCollection.getOverviewInformation());
+		StringBuilder sb = new StringBuilder();
+		masterCollection.accept(new OverviewPrinter(sb));
+		System.out.print(sb);
 		System.out.println("\n===Contents===\n");
-		System.out.print(masterCollection.getDetailedInformation());
+		sb = new StringBuilder();
+		masterCollection.accept(new DetailedPrinter(sb));
+		System.out.print(sb);
 		System.out.println("\n===After change===\n");
 
 		changedArticle.setTitle("Harder, Better, Faster, Stronger? Doping controls loosened");

ueb07_news_example/src/model/Article.java

@@ -20,7 +20,12 @@ public class Article extends NewsItem {
 		this.title = title;
 		this.author = author;
 	}
-	
+
+	@Override
+	public void accept(NewsItemVisitor visitor) {
+		visitor.visit(this);
+	}
+
 	/**
 	 * Get the author of the article.
 	 * @return author
@@ -36,19 +41,4 @@ public class Article extends NewsItem {
 	public String getContent() {
 		return content;
 	}
-
-	@Override
-	public String getOverviewInformation() {
-		return "Article: " + this.getTitle() + ", Author: " + this.getAuthor();
-	}
-
-	@Override
-	public String getDetailedInformation() {
-		StringBuilder builder = new StringBuilder();
-		builder.append("###" + this.getTitle() + "###");
-		builder.append("\n");
-		builder.append(this.getContent());
-		builder.append("\n");
-		return builder.toString();
-	}
 }

ueb07_news_example/src/model/DetailedPrinter.java

@@ -0,0 +1,50 @@
+package model;
+
+public class DetailedPrinter implements NewsItemVisitor {
+    StringBuilder sb;
+
+    public DetailedPrinter(StringBuilder sb) {
+        this.sb = sb;
+    }
+
+    /**
+     * Print details about news article.
+     */
+    @Override
+    public void visit(final Article article) {
+        sb.append("###")
+                .append(article.getTitle())
+                .append("###");
+        sb.append("\n");
+        sb.append(article.getContent());
+        sb.append("\n");
+    }
+
+    /**
+     * Print details about image.
+     */
+    @Override
+    public void visit(final Image image) {
+        sb.append("###")
+                .append(image.getTitle())
+                .append("###");
+        sb.append("\n");
+        sb.append(image.renderToString());
+        sb.append("\n");
+    }
+
+    /**
+     * Print details about news collection.
+     */
+    @Override
+    public void visit(final NewsCollection collection) {
+        sb.append("###")
+                .append(collection.getTitle())
+                .append("###");
+        sb.append("\n");
+        for (NewsItem item : collection.getNewsItems()) {
+            item.accept(this);
+            sb.append("\n");
+        }
+    }
+}

ueb07_news_example/src/model/Image.java

@@ -19,6 +19,11 @@ public class Image extends NewsItem {
 		this.height = height;
 		this.author = author;
 	}
+
+	@Override
+	public void accept(NewsItemVisitor visitor) {
+		visitor.visit(this);
+	}
 	
 	/**
 	 * Get the author of the image.
@@ -54,26 +59,4 @@ public class Image extends NewsItem {
 		 */
 		return " /\\_/\\ \n( o.o )\n > ^ < ";
 	}
-
-	/**
-	 * Print a list showing information about all directly or transitively
-	 * referenced items in the given collection.
-	 */
-	@Override
-	public String getOverviewInformation() {
-		return "Image: " + this.getTitle()
-					+ ", Resolution: " + this.getWidth() 
-					+ "x" + this.getHeight() 
-					+ ", Author: " + this.getAuthor();
-	}
-
-	@Override
-	public String getDetailedInformation() {
-		StringBuilder builder = new StringBuilder();
-		builder.append("###" + this.getTitle() + "###");
-		builder.append("\n");
-		builder.append(renderToString());
-		builder.append("\n");
-		return builder.toString();
-	}
 }

ueb07_news_example/src/model/NewsCollection.java

@@ -10,7 +10,12 @@ public class NewsCollection extends NewsItem {
 	public NewsCollection(String topic) {
 		this.title = topic;
 	}
-	
+
+	@Override
+	public void accept(NewsItemVisitor visitor) {
+		visitor.visit(this);
+	}
+
 	/**
 	 * Get the list of items stored in this collection.
 	 * @return items stored in this collection
@@ -28,31 +33,4 @@ public class NewsCollection extends NewsItem {
 		newsItems.add(item);
 		return this;
 	}
-	
-	/**
-	 * Print a list showing information about all directly or transitively
-	 * referenced items in the given collection.
-	 */
-	public String getOverviewInformation() {
-		StringBuilder builder = new StringBuilder();
-		builder.append("###" + this.getTitle() + "###");
-		builder.append("\n");
-		for (NewsItem item : this.getNewsItems()) {
-			builder.append(item.getOverviewInformation());
-			builder.append("\n");
-		}
-		return builder.toString();
-	}
-
-	@Override
-	public String getDetailedInformation() {
-		StringBuilder builder = new StringBuilder();
-		builder.append("###" + this.getTitle() + "###");
-		builder.append("\n");
-		for (NewsItem item : this.getNewsItems()) {
-			builder.append(item.getDetailedInformation());
-			builder.append("\n");
-		}
-		return builder.toString();
-	}	
 }

ueb07_news_example/src/model/NewsItem.java

@@ -8,6 +8,8 @@ public abstract class NewsItem {
 		super();
 	}
 
+	public abstract void accept(NewsItemVisitor visitor);
+
 	/**
 	 * Get the topic of the collection.
 	 * @return
@@ -19,14 +21,4 @@ public abstract class NewsItem {
 	public void setTitle(String newTitle) {
 		title = newTitle;
 	}
-
-	/**
-	 * Get overview information about the news item.
-	 */
-	public abstract String getOverviewInformation();
-
-	/**
-	 * Get the contents of the news item.
-	 */	
-	public abstract String getDetailedInformation();
 }

ueb07_news_example/src/model/NewsItemVisitor.java

@@ -0,0 +1,7 @@
+package model;
+
+public interface NewsItemVisitor {
+    void visit(final Article article);
+    void visit(final Image image);
+    void visit(final NewsCollection collection);
+}

ueb07_news_example/src/model/OverviewPrinter.java

@@ -0,0 +1,52 @@
+package model;
+
+public class OverviewPrinter implements NewsItemVisitor {
+    final StringBuilder sb;
+
+    /**
+     * @param sb StringBuilder to print overview into.
+     */
+    public OverviewPrinter(StringBuilder sb) {
+        this.sb = sb;
+    }
+
+    /**
+     * Print overview about news article.
+     */
+    @Override
+    public void visit(final Article article) {
+        sb.append("Article: ")
+                .append(article.getTitle())
+                .append(", Author: ")
+                .append(article.getAuthor());
+    }
+
+    /**
+     * Print overview about image.
+     */
+    @Override
+    public void visit(final Image image) {
+        sb.append("Image: ")
+                .append(image.getTitle())
+                .append(", Resolution: ")
+                .append(image.getWidth())
+                .append("x")
+                .append(image.getHeight())
+                .append(", Author: ")
+                .append(image.getAuthor());
+    }
+
+    /**
+     * Print overview about news collection.
+     */
+    @Override
+    public void visit(final NewsCollection collection) {
+        sb.append("###")
+                .append(collection.getTitle())
+                .append("###\n");
+        for (NewsItem item : collection.getNewsItems()) {
+            item.accept(this);
+            sb.append("\n");
+        }
+    }
+}