import java.util.Iterator;

import java.util.NoSuchElementException;

public class MyArrayList<T> implements Iterable<T> {

    //默认数组大小

     private static final int DEFAULT_CAPACITY=;

     //表大小

     private int theSize;

     //数组存储

     private T[] theItems;

     //初始化表

     public MyArrayList(){

         doClear();

     }

    private void doClear() {

        // TODO Auto-generated method stub

        theSize=;

        ensureCapacity(DEFAULT_CAPACITY);

    }

    //清空表

    public void Clear(){

        doClear();

    }

    //判断是否为空

    public boolean isEmpty(){

        return size()==;

    }

    //将此 ArrayList 实例的容量调整为列表的当前大小

    public void trimToSize(){

        ensureCapacity(size());

    }

    public T get(int index){

        if(index<||index>size()){

            throw new ArrayIndexOutOfBoundsException();

        }

        return theItems[index];

    }

    public T set(int index,T val){

        if(index<||index>size()){

            throw new ArrayIndexOutOfBoundsException();

        }

        T old=theItems[index];

        theItems[index]=val;

        return old;

    }

    public boolean add(T val){

        add(size(),val);

        return true;

    }

    public  void add(int index, T val) {

        // TODO Auto-generated method stub

        if(theItems.length==size()){

            ensureCapacity(size()*+);

        }

        for(int i=theSize;i>index;i--){

            theItems[i]=theItems[i-];

        }

        theItems[index]=val;

        theSize++;

    }

    public T remove(int index){

        T removedItem=theItems[index];

        for(int i=index;i<size()-;i++){

            theItems[i]=theItems[i+];

        }

        theSize--;

        return removedItem;

    }

    public java.util.Iterator<T> iterator(){

        return  new ArrayListIterator();

    }

    private class ArrayListIterator implements java.util.Iterator<T>{

        private int current=;

        public boolean hasNext(){

            return current<size();

        }

        public T next(){

            if(!hasNext()){

                throw new NoSuchElementException();

            }

            return theItems[current++];

        }

        public void remove(){

            MyArrayList.this.remove(--current);

        }

    }

    private void ensureCapacity(int newCapacity) {

        // TODO Auto-generated method stub

        if(newCapacity<theSize){

            return;

        }

        T[] old=theItems;

        theItems=(T[]) new Object[newCapacity];

        for(int i=;i<size();i++){

            theItems[i]=old[i];

        }

    }

    private int size() {

        // TODO Auto-generated method stub

        return theSize;

    }

}