封装一个简单的动态数组

package com.immoc;

import java.util.ArrayList;
import java.util.List;

/**
 * 实现动态数组
 * */
public class Array <E> {

    private E[]data;;
    private int size;
    public Array(int capacity){
        data = (E[]) new  Object[capacity];
        size = 0;
    }
    public Array(){
        this(10);
    }
    public int getSize(){
        return size;
    }
    public int getCapacity(){
      return data.length;
    }
    public boolean isEmpty(){
        return size==0;
    }
    //在数组的最后添加一个元素
    public void addList(E e){
        add(size, e);
    }
    //在数组的最后加入一个元素
    public void addFirst(E e){
        add(0, e);
    }
    //数组中插入一个元素
    public void add(int index,E val){

        if(index<0||index>size){throw new IllegalArgumentException("传入的参数超过数组的长度");}
        if(size==data.length){resize(2*getCapacity());}
        for(int i = size - 1;i >= index;i --){
            data[i + 1] = data[i];
        }
        data[index]=val;
        size++;
    }
    //查询某个元素
    public E query(int index){
        if(index < 0 || index >= size){throw new NullPointerException("null");}
        return data[index];
    }
    //修改某个元素
    public void update(int index, E val){
        if(index < 0 || index >= size){throw new NullPointerException("null");}
        data[index]  = val;
    }
    //toString方法
    @Override
    public String toString(){
        StringBuffer sb = new StringBuffer();
        sb.append("数组的长度:"+size+"\t" + "数组的容量："+data.length + "\n");
        sb.append("[");
        for (int i = 0; i < size; i++) {
            sb.append(data[i]);
            if(i !=size-1){
                sb.append(",");
            }
        }
        sb.append("]");
        return sb.toString();
    }
    //是否包含
    public boolean isContain(E val){
        for (int i = 0; i < size; i++) {
            if(val.equals(data[i])){
                return true;
            }
        }
        return false;
    }

    //删除某个
    public E delete( int index ){
        if(index < 0 || index >= size){throw new NullPointerException("null");}
        E ret = data[index];
        for (int i = index; i < size; i++) {
            data[i] = data[i+1];
        }
        size --;
        if (size < data.length/2){
            resize(size);
        }
        return ret;
    }
    //寻找下标
    public int findIndex(E val){
        Array a = new Array();
        for (int i = 0; i <size; i++) {
            if (val.equals(data[i])){
                return i;
            }
        }
        return -1;
    }
    //寻找所有下标
    public List findIndexs(E val){
        List l = new ArrayList();
        for (int i = 0; i <size ; i++) {
            if(val.equals(data[i])){
                l.add(i);
            }
        }
        return l;
    }
    //改变容量长度
    public void resize(int capacity){
        E[] newData = (E[]) new Object[capacity];
        for (int i = 0; i <size; i++) {
            newData[i] = data[i];
        }
        data = newData;
    }



}