foreach循环详解

在Java1.5+中,foreach循环非常实用.

 

 public class Demo <T> implements Iterable<T>, Iterator<T> {
     T[] array;
     int length;
     int index;

     Demo(T[] param){
         array = param;
         length = array.length;
     }

     public static void main(String[] args) {
         Demo<String> demo = new Demo<String>(new String[]{"aaa","bbb"});
         for(String str : demo){
             System.out.println(str);
         }
     }

     public Iterator<T> iterator(){
         return this;
     }

     public void remove(){
     }

     public boolean hasNext(){
         index = (index+1)%(length+1);
         if(index==0)return false;
         return true;
     }

     public T next(){
         return array[index-1];
     }
 }

 /*output:
 aaa
 bbb
 */

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上述代码等价于以下形式

     public static void main() {
         Demo<String> demo = new Demo<String>(new String[]{"aaa","bbb"});
         Iterator<String> iterator = demo.iterator();
         whlie(iterator.hasNext()){
             String tmp = iterator.next();
             System.out.println(tmp);
         }
     }