add iterator DP

Liu Yuning · Liu Yuning · commit 77270c151bfc · 2017-05-21T10:09:46.000+08:00
diff --git a/src/designpattern/iterator/Aggregate.java b/src/designpattern/iterator/Aggregate.java
@@ -0,0 +1,13 @@
+package designpattern.iterator;
+
+/**
+ * 聚集接口
+ * 
+ * @author liu yuning
+ *
+ * @param <T>
+ */
+public interface Aggregate<T> {
+
+    public Iterator<T> createIterator();
+}
diff --git a/src/designpattern/iterator/ConcreteAggregate.java b/src/designpattern/iterator/ConcreteAggregate.java
@@ -0,0 +1,35 @@
+package designpattern.iterator;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * 具体聚集类
+ * 
+ * @author liu yuning
+ *
+ * @param <T>
+ */
+public class ConcreteAggregate<T> implements Aggregate<T> {
+
+    private List<T> items = new ArrayList<T>();
+
+    @Override
+    public Iterator<T> createIterator() {
+	// TODO Auto-generated method stub
+	return new ConcreteIterator<T>(this);
+    }
+
+    public int count() {
+	return items.size();
+    }
+
+    public T getItems(int index) {
+	return items.get(index);
+    }
+
+    public void setItems(T item) {
+	items.add(item);
+    }
+
+}
diff --git a/src/designpattern/iterator/ConcreteIterator.java b/src/designpattern/iterator/ConcreteIterator.java
@@ -0,0 +1,62 @@
+package designpattern.iterator;
+
+/**
+ * 具体迭代器类，给出一种具体迭代的实现方式。思考：迭代器表示的是一种迭代的行为，而聚集则是真正要被迭代的数据集合。
+ * 之所以要将迭代器和聚集分开，就是为了将行为与数据分开。 可类比Java中Iterator与Iterable的关系进行理解
+ * 
+ * @author liu yuning
+ *
+ * @param <T>
+ */
+public class ConcreteIterator<T> implements Iterator<T> {
+
+    private ConcreteAggregate<T> concreteAggregate;
+    private int current = 0;
+
+    public ConcreteIterator(ConcreteAggregate<T> concreteAggregate) {
+	this.setConcreteAggregate(concreteAggregate);
+    }
+
+    @Override
+    public T first() {
+	return concreteAggregate.getItems(0);
+    }
+
+    @Override
+    public T next() {
+	current++;
+
+	if (current < concreteAggregate.count()) {
+	    return concreteAggregate.getItems(current);
+	}
+
+	return null;
+    }
+
+    @Override
+    public boolean isDone() {
+	return current >= concreteAggregate.count() ? true : false;
+    }
+
+    @Override
+    public T currentItem() {
+	return concreteAggregate.getItems(current);
+    }
+
+    public ConcreteAggregate<T> getConcreteAggregate() {
+	return concreteAggregate;
+    }
+
+    public void setConcreteAggregate(ConcreteAggregate<T> concreteAggregate) {
+	this.concreteAggregate = concreteAggregate;
+    }
+
+    public int getCurrent() {
+	return current;
+    }
+
+    public void setCurrent(int current) {
+	this.current = current;
+    }
+
+}
diff --git a/src/designpattern/iterator/Iterator.java b/src/designpattern/iterator/Iterator.java
@@ -0,0 +1,20 @@
+package designpattern.iterator;
+
+/**
+ * 迭代器接口
+ * 
+ * @author liu yuning
+ *
+ * @param <T>
+ */
+public interface Iterator<T> {
+
+    public T first();
+
+    public T next();
+
+    public boolean isDone();
+
+    public T currentItem();
+
+}
diff --git a/src/designpattern/iterator/IteratorClient.java b/src/designpattern/iterator/IteratorClient.java
@@ -0,0 +1,28 @@
+package designpattern.iterator;
+
+/**
+ * 迭代器客户端
+ * 
+ * @author liu yuning
+ *
+ */
+public class IteratorClient {
+    public static void main(String[] args) {
+	ConcreteAggregate<String> bus = new ConcreteAggregate<String>();
+
+	bus.setItems("大鸟");
+	bus.setItems("小菜");
+	bus.setItems("行李");
+	bus.setItems("老外");
+	bus.setItems("公交内部员工");
+	bus.setItems("小偷");
+
+	Iterator<String> iterator = new ConcreteIterator<String>(bus);
+
+	while (!iterator.isDone()) {
+	    System.out.println(iterator.currentItem() + "请买票！");
+	    iterator.next();
+	}
+    }
+
+}
