import org.omg.CORBA.PUBLIC_MEMBER;

import java.io.Serializable;

import java.util.*;

import java.util.function.Consumer;

import java.util.function.Predicate;

import java.util.function.UnaryOperator;

import java.util.stream.Stream;

public class MyArrayList<T> {

    int size;

    private Object array[];

    private static final Object[] EMPTY_ARRAY={};

    public MyArrayList()

    {

        this(10);

    }

    public MyArrayList(int initCapcity) {

        if (initCapcity < 0)

            throw new IllegalArgumentException("initCapcity必须大于0");

        else if (initCapcity==0)

        {

            this.array=EMPTY_ARRAY;

        }else {

            array=new Object[initCapcity];

        }

    }

    public MyArrayList(Collection<? extends T> c)

    {

        array=c.toArray();

        if((size=array.length)!=0)

        {

            if (array.getClass()!=Object[].class)

            {

                array=Arrays.copyOf(array,size,Object[].class);

            }

        }else {

            this.array=EMPTY_ARRAY;

        }

    }

    public boolean isEmpty()

    {

        return size==0;

    }

    public int size() {

        return size;

    }

    public boolean add(Object obj)

    {

        ensureCapacity();

        array[size++]=obj;

        return true;

    }

    public void add(int index,Object object)

    {

        rangeCheck(index);

        ensureCapacity();

        System.arraycopy(array,index,array,index+1,size-index);

        array[index]=object;

        size++;

    }

    public Object remove(int index)

    {

        rangeCheck(index);

        Object oldObject=array[index];

        if (array.length-index-1>0)

        {

            System.arraycopy(array,index+1,array,index,array.length-index-1);

        }

        array[size--]=null;

        return oldObject;

    }

    public boolean remove(Object object)

    {

        if (object==null)

        {

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

            {

                if (array[i]==null)

                    remove(i);

                return true;

            }

        }else {

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

            {

                if (object.equals(array[i]))

                {

                    remove(i);

                    return true;

                }

            }

        }

        return  false;

    }

    public Object get(int index)

    {

        rangeCheck(index);

        return array[index];

    }

    public void set(int index,Object object)

    {

        rangeCheck(index);

        Object oldObject=array[index];

        array[index]=object;

    }

    //判断索引是否越界

    public void rangeCheck(int index)

    {

        if (index>=size||index<0)

            throw new IndexOutOfBoundsException("索引不在范围内");

    }

    //数组容量与size相等时进行扩容

    public void ensureCapacity()

    {

        if (size==array.length)

        {

            Object []  newArray=new Object[2*size+1];

            System.arraycopy(array,0,newArray,0,array.length);

            array=newArray;

        }

    }

}

import java.util.ArrayList;

public class Demo1 {

    public static void main(String[] args)

    {

        MyArrayList myArrayList=new MyArrayList<String>();

        myArrayList.add("aaaaa");

        myArrayList.add("bbbbb");

        System.out.println(myArrayList.get(0));

        System.out.println(myArrayList.get(1));

        myArrayList.remove(0);

        System.out.println(myArrayList.get(0));

        myArrayList.set(0,"xujinfeng");

        System.out.println(myArrayList.get(0));

        System.out.println(myArrayList.size());

    }

}