持有对象（容器）——适配器（反向迭代器使用）

来源：互联网发布：720全景源码编辑：程序博客网时间：2024/05/19 09:02

应用：

当你有一个接口并需要另一个接口时，编写适配器可以解决。

（我希望在默认的前向迭代器的基础上，添加产生反向迭代器的能力，因此不能使用覆盖，而是添加了一个能够产生Iterable对象的方法，该对象可以用于foreach语句。）

代码编写：

a:类继承class ReversibleArrayList<T> extends ArrayList<T>，再写返回类型为iterator<Object>()方法，之后有提示

class ReversibleArrayList<T> extends ArrayList<T>{  // 反向迭代器private static final long serialVersionUID = 1L;public ReversibleArrayList(Collection<T> c){ super(c); }public Iterable<T> reversed(){return new Iterable<T>() {public Iterator<T> iterator() {return new Iterator<T>() {int current = size() - 1;public boolean hasNext() {return current > -1;}public T next() {return get(current--);}public void remove() {throw new UnsupportedOperationException();}};}};}}

测试：

public class AdapterMethodIdiom {public static void main(String[] args) {ReversibleArrayList<String> ral = new ReversibleArrayList<String>(Arrays.asList("To be or not to be".split(" ")));for (String string : ral)   //放在foreach语句中，将得到（默认的）向前迭代器System.out.print(string+" ");System.out.println();for (String string : ral.reversed()) {System.out.print(string+" ");} }}

打印：

b:编写类继承class IterableClass implements Iterable<Object>会直接添加返回类型为Iterator<Object>的方法，return Iterator<Object>(){hasNext(),next(),remove()}

public class IterableClass implements Iterable<Object>{protected String[] words = ("And that is how " + "we know the Earth to be banana-shaped.").split(" ");public Iterator<Object> iterator() {return new Iterator<Object>() {private int index = 0;public boolean hasNext() {return index < words.length;}public String next() {return words[index++];}public void remove() {throw new UnsupportedOperationException();}};}}

应用：

public class MultiIterableClass extends IterableClass{public Iterable<Object> reversed(){return new Iterable<Object>() {public Iterator<Object> iterator() {return new Iterator<Object>() {int current = words.length-1;public void remove() {throw new UnsupportedOperationException();}public String next() {return words[current--];}public boolean hasNext() { return current > -1;}};}};}public Iterable<String> randomized(){return new Iterable<String>() {public Iterator<String> iterator() {List<String> shuffled = new ArrayList<String>(Arrays.asList(words));Collections.shuffle(shuffled);//打乱数组return shuffled.iterator();}};}public static void main(String[] args) {MultiIterableClass mic = new MultiIterableClass();for (Object string : mic.reversed()) System.out.print(string.toString()+" ");System.out.println();for (String string : mic.randomized())System.out.print(string+" ");System.out.println();for (Object object : mic) {System.out.print(object.toString()+" ");}}}

控制台打印

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