java 增强型for循环

1、必须继承AbstractCollection抽象类或其子类 并重写iterator方法（子类为重写iterator方法的）

2、循环是使用iterator方法返回的迭代器

3、迭代器实现iterator接口 并重写hasNext和next方法

AbstractList重写了iterator方法，故不用重写iterator。

AbstractSet:

/**  * @author star  * @since 6/27/2018 3:51 PM  */ public class IteratorTest extends AbstractSet<String>{private String [] strs={
   "1","2"};
    @Override
    public Iterator<String> iterator() {return new MyIterator();
    }@Override
    public int size() {return strs.length;
    }public class MyIterator implements Iterator<String> {int currentIndex=0;
        String next;

        @Override
        public boolean hasNext() {return currentIndex!=strs.length;
        }@Override
        public String next() {return strs[++currentIndex];
        }}
}

public static void main(String[] args) {IteratorTest iteratorTest=new IteratorTest();
    for(String str:iteratorTest){System.out.println(str);
    }
}