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
*/

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);
        }
    }