/**

 * 顺序表，重点是数组动态扩容，插入

 * 底层采用数组，长度可以动态变化,此处采用增长一倍，而java.util.ArrayList每次增长50%

 *  int newCapacity = oldCapacity + (oldCapacity >> 1);

 *

 */

public class ArrayList implements List{

     private Object[] elementData;//底层数组

     private int size;//元素个数

     public ArrayList(int initialCapacity) {

        //给数组分配指定数量空间

         elementData = new Object[initialCapacity];

        //指定顺序表元素个数，默认是0

        //size = 0;

     }

     public ArrayList() {

       //没有指定长度，默认initialCapacity是4

         this(4);

      //没有指定长度，长度是0

//         elementData = new Object[]{};

     }

    @Override

    public int size() {

        // TODO Auto-generated method stub

        return size;

    }

    @Override

    public Object get(int i) {

        if(i<0||i>size-1){

            throw new RuntimeException("数组指针越界:"+i);

        }

        return elementData[i];

    }

    @Override

    public boolean isEmpty() {

        // TODO Auto-generated method stub

        return size == 0;

    }

    @Override

    public boolean contains(Object e) {

        // TODO Auto-generated method stub

        return false;

    }

    @Override

    public int indexOf(Object e) {

        // TODO Auto-generated method stub

        return 0;

    }

    @Override

    public void add(int i, Object e) {

        if(i<0||i>size){

            throw new RuntimeException("数组指针越界异常:"+i);

        }

       if(size == elementData.length)

        {

            grow();

        }

        for(int j =size ; j>i  ; j--){

            elementData[j] = elementData[j-1];

        }

        elementData[i] = e;

        size++;

    }

    @Override

    public void add(Object e) {

        this.add(size, e);

//    //动态扩容

//    if(size == elementData.length)

//    {

//        grow();

//    }     //        elementData[size] = e;

//        size++;

//        //System.out.println("length="+elementData.length);

    }

    public void grow(){

//        Object[] newArr = new Object[size*2];

//        for(int i = 0; i<size;i++){

//            newArr[i] = elementData[i];

//        }

//        elementData = newArr;

    elementData = Arrays.copyOf(elementData, elementData.length*2);

    }

}