请教下Iterator问题
为什么用Iteator it = coll.iterator(); 会用，不理解1.因为Iterator 是接口 接口不能实例化 而coll对象中的 hasnext()，next()在API中并没有显示implements Itreator 也没有重写hasnext();next(),
2. ComperTo方法需要重写才能比较 为什么hasnext(),next()不需要重写呢
3. 如果我自己定义个Arr类implements Iterator 我需要重写hasnext,next方法吗 next方法返回类型应该是什么
4.谢谢回答 iterator --------------------编程问答-------------------- 不要把iterator单单理解为一个接口，把它看成是一个容器，就很好理解了，实现Iterator肯定要重写方法的，next返回类型为Object --------------------编程问答-------------------- 1.iterator（）方法返回的是个迭代器，实现了Iterator接口，Iterator接口有hasnext（），next（），remove（）三个方法，而Iterator接口与Collection没有任何父子关系。所以实现collection接口的类没有实现了以上的那三个iterator方法，实现这个方法的只是Iterator.三个方法在AbstractCollection里面重写了。
2.如果是一个非抽象类,实现一个接口或者继承抽象类,此非抽象类,必须实现接口所有方法或者抽象类的所有抽象方法的.这是java的语法规定.
3.
AbstractList.class：
public Iterator<E> iterator() {
return new Itr();
}
private class Itr implements Iterator<E> {
/**
* Index of element to be returned by subsequent call to next.
*/
int cursor = 0;
/**
* Index of element returned by most recent call to next or
* previous. Reset to -1 if this element is deleted by a call
* to remove.
*/
int lastRet = -1;
/**
* The modCount value that the iterator believes that the backing
* List should have. If this expectation is violated, the iterator
* has detected concurrent modification.
*/
int expectedModCount = modCount;
public boolean hasNext() {
return cursor != size();
}
public E next() {
checkForComodification();
try {
E next = get(cursor);
lastRet = cursor++;
return next;
} catch (IndexOutOfBoundsException e) {
checkForComodification();
throw new NoSuchElementException();
}
}
public void remove() {
if (lastRet == -1)
throw new IllegalStateException();
checkForComodification();
try {
AbstractList.this.remove(lastRet);
if (lastRet < cursor)
cursor--;
lastRet = -1;
expectedModCount = modCount;
} catch (IndexOutOfBoundsException e) {
throw new ConcurrentModificationException();
}
}
final void checkForComodification() {
if (modCount != expectedModCount)
throw new ConcurrentModificationException();
}
}
补充：Java , Java SE
