java 自定义容器，实现foreach

import java.util.Arrays;
import java.util.Iterator;

public class ArrayList implements Iterable<Integer> {
    public int size;
    public int current = 0;
    Object[] objects = new Object[2];
    public void add(Object o) {
        //当index超出最初定义数组的长度时，自动扩容
        if(size == objects.length){
            System.out.println("extend................");
            System.out.println(size);
            objects = Arrays.copyOf(objects, objects.length + (objects.length << 1));
            System.out.println(objects.length);
        }
        objects[size] = o;
        size++;
    }

    public int size(){ return size; }

    public int get(int i) {return (int)objects[i]; }

    public Iterator<Integer> iterator() {
        class iter implements Iterator<Integer> {
            @Override
            public boolean hasNext() {
                return (current < size);
            }

            @Override
            public Integer next() {
                return (int)objects[current++];
            }

            @Override
            public void remove() {

            }
        }

        return new iter();
    }

    public static void main(String[] args) {
        ArrayList a = new ArrayList();
        a.add(23);
        a.add(67);
        a.add(98);
        a.add(989);
        a.add(9897);
//        for (int i = 0; i < a.size(); i++)
//            System.out.println(a.get(i));
        for (Integer abc : a) {
            System.out.println(abc);
        }
    }
}