My self-study record: the case of Java collections--iterative mode

package com.iotek.myiterator;

public interface Iterator<T> {
 public boolean hasNext();//Determine whether there is a next element
 public T next();//Get the next element

}

package com.iotek.myiterator;

public interface List<T> {
 public void add(T obj);//Add elements to the container
 public T get(int index);//Get the specified position element
 public int size();//Get the number of elements in the container
 public Iterator<T> iterator();//Get the specific iterator object
 
}

package com.iotek.myiterator;

public class MyIterator<T> implements Iterator<T> {
 private List<T> list=null;
 private int index=0;//Access the current subscript of the element in the container
 //When creating an iterator object, accept the iterable Container object
 public MyIterator(List<T> list){
  this.list=list;
 }
 @Override
 public boolean hasNext() {
 
  return index<list.size();
 }

 @Override
 public T next() {
 
  return list.get(index++);
 }

}

package com.iotek.myiterator;

public class ArrayList<T> implements List<T> {
 private Object [] obj=null;
 private int index;
 private int size;
 public ArrayList(){
  obj=new Object[10];
  index=0;
  size=0;
 }
 @Override
 public void add(T obj) {
  this.obj[index++]=obj;
  size++;
  
 }
 @SuppressWarnings("unchecked")
 @Override
 public T get(int index) {
  
  return (T)obj[index];
 }
 @Override
 public int size() {
 
  return size;
 }
 @Override
 public Iterator<T> iterator() {
  return new MyIterator<T>(this);
 } 

}

package com.iotek.myiterator;

public class Test {

 public static void main(String[] args) {
  ArrayList<String> nameList = new ArrayList<String>();
  nameList.add("zhang shan");
  nameList.add("lisi");
  nameList.add("wang wu");
  Iterator<String> it=nameList.iterator();
  while(it.hasNext())
   System.out.println(it.next());

 }