auto commit

notes/设计模式.md

@@ -496,7 +496,80 @@ public class Client {
 
 ### 意图
 
-提供一种一致的访问聚合对象元素的方法，并且不暴露聚合对象的内部表示。
+提供一种顺序访问聚合对象元素的方法，并且不暴露聚合对象的内部表示。
+
+### 类图
+
+<div align="center"> <img src="../pics//b0f61ac2-a4b6-4042-9cf0-ccf4238c1ff7.png"/> </div><br>
+
+### 实现
+
+```java
+public interface Aggregate {
+    Iterator createIterator();
+}
+```
+
+```java
+public class ConcreteAggregate implements Aggregate {
+
+    private Integer[] items;
+
+    public ConcreteAggregate() {
+        items = new Integer[10];
+        for (int i = 0; i < items.length; i++) {
+            items[i] = i;
+        }
+    }
+
+    @Override
+    public Iterator createIterator() {
+        return new ConcreteIterator<Integer>(items);
+    }
+}
+```
+
+```java
+public interface Iterator<Item> {
+    Item next();
+
+    boolean hasNext();
+}
+```
+
+```java
+public class ConcreteIterator<Item> implements Iterator {
+
+    private Item[] items;
+    private int position = 0;
+
+    public ConcreteIterator(Item[] items) {
+        this.items = items;
+    }
+
+    @Override
+    public Object next() {
+        return items[position++];
+    }
+
+    @Override
+    public boolean hasNext() {
+        return position < items.length;
+    }
+}
+```
+
+```java
+public class Client {
+    public static void main(String[] args) {
+        Aggregate aggregate = new ConcreteAggregate();
+        Iterator<Integer> iterator = aggregate.createIterator();
+        while (iterator.hasNext()) {
+            System.out.println(iterator.next());
+        }
+    }
+}
+```
 
 ### JDK