1.首先定義一個容器Collection接口.
package com.njupt.zhb.learn.iterator; public interface Collection { void add(Object o); int size(); Iterator iterator(); }
2.定義一個Iterator迭代器的接口
package com.njupt.zhb.learn.iterator; public interface Iterator { Object next(); boolean hasNext(); }
3.定義一個ArrayList,實現Collection接口,並寫一個實現了Iterator接口的內部類。
package com.njupt.zhb.learn.iterator; import com.njupt.zhb.learn.iterator.Collection; public class ArrayList implements Collection { Object[] objects = new Object[10]; int index = 0; public void add(Object o) { if(index == objects.length) { Object[] newObjects = new Object[objects.length * 2]; System.arraycopy(objects, 0, newObjects, 0, objects.length); objects = newObjects; } objects[index] = o; index ++; } public int size() { return index; } public Iterator iterator() { return new ArrayListIterator(); } private class ArrayListIterator implements Iterator { private int currentIndex = 0; @Override public boolean hasNext() { if(currentIndex >= index) return false; else return true; } @Override public Object next() { Object o = objects[currentIndex]; currentIndex ++; return o; } } }
4.寫測試程式TestMain
package com.njupt.zhb.learn.iterator; import com.njupt.zhb.learn.iterator.ArrayList; public class TestMain { public static void main(String[] args) { Collection c = new ArrayList(); for(int i=0; i<15; i++) { c.add("string "+i); } System.out.println(c.size()); Iterator it = c.iterator(); while(it.hasNext()) { Object o = it.next(); System.out.println(o.toString() + " "); } } }
運作結果:
15 string 0 string 1 string 2 string 3 string 4 string 5 string 6 string 7 string 8 string 9 string 10 string 11 string 12 string 13 string 14
從以上可以看出,設計模式到處用到物件導向中的多態性。介面呼叫子類別中的函數。
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