package com.customArray0905;
public class CustomArraryList<E> {
 Object[] data;
 int Size;

 public int getSize() {
  return Size;
 }

 //返回数组下标为index的元素的值
 public E get(int index) {
  if(index<0 || index>=Size) {
   throw new IndexOutOfBoundsException();
   //否则return null
  }
  return (E) data[index];
 }

 //自定义更改下标为index的元素值的方法
 public void set(int index, E e) {
  if(index<0 || index>=Size) {
   throw new IndexOutOfBoundsException();
   //否则return null
  }
  data[index] = e;
 }

 public void add(E e) {
  ///创建新对象 容量扩大一个
  Object[] newdata = new Object[Size + 1];
  //将array中的元素重新存入更新容量后的newArray数组中去
  for (int i = 0; i < Size; i++) {
   newdata[i] = data[i];
  }
  data = newdata;
  data[Size++] = e;
 }
 //自定义移除下标为index的元素的方法
 public void remove(int index) {
  ///创建新对象 容量减少一个
  Object[] newdata = new Object[Size - 1];
  int j = 0;

  //判断index大小是否合适存在数组中
  if(index<0 || index>=Size) {
   throw new IndexOutOfBoundsException();
   //否则return null
  }
   //得到老对象里下标之前的所有元素并存入新对象
   for (int i = 0; i < index; i++) {
    newdata[j] = data[i];
    j++;
   }
   //得到老对象里下标之后的所有元素并存入新对象
   for (int i = index + 1; i < Size; i++) {
    newdata[j] = data[i];
    j++;
   }
   data = newdata;
   Size--;
 }
 //清除array中所有的元素
 public void clear() {
  for(int i = 0;i<Size;i++) {
   data[i] = null;
  }
  Size = 0;
 }

 public static void main(String[] args) {
  CustomArraryList<String> myList = new CustomArraryList<>();
  //Add
  System.out.println("测试1,ADD方法");
  myList.add("1");
  myList.add("2");
  myList.add("3");
  myList.add("4");
  myList.add("5");
  for (int i = 0; i < myList.getSize(); i++) {
   System.out.println(myList.get(i));
  }

  //Remove,Set
  myList.remove(2);
  myList.set(3, "7");
  System.out.println("测试2,移除index=2的数据,并设置index=3的数据值为7,");
  for (int i = 0; i < myList.getSize(); i++) {
   System.out.println(myList.get(i));
  }

  //Clear
  myList.clear();
  myList.add("1");
  for (int i = 0; i < myList.getSize(); i++) {
   System.out.println("测试3,clear方法，仅剩下新添加数据 "+myList.get(i));
  }
  //抛出错误
  System.out.println("测试4,抛出set错误");
  myList.set(2,"2");

 }
}