这里没有扩展这个AbstractList，你可以自己实现很多的方法什么的，这是模仿ArrayList的一些方法
public class MyArrayList {
 
    private Object[] datas;// 存放数据
    private int size;// 存放大小
 
    public MyArrayList() {
        this.size = 0;
        //这个地方你可以加一个常量
        datas = new Object[100000];
    }
 
    public boolean add(Object obj) {
        ensureCapacity(size + 1);
        datas[size++] = obj;
        return true;
    }
     
    public Object remove(int index){
        RangeCheck(index);
        Object oldValue =  datas[index];
 
        int numMoved = size - index - 1;
        if (numMoved > 0)
            System.arraycopy(datas, index+1, datas, index,
                     numMoved);
        datas[--size] = null;
 
        return oldValue;
    }
     
    public Object set(int index,Object obj){
        RangeCheck(index);
        Object oldValue =  datas[index];
         
        datas[index] = obj;
        return oldValue;
    }
    public int size() {
        return size;
    }
     
    public void clear(){
        for (int i = 0; i < datas.length; i++) {
            datas[i] = null;
        }
         
        size = 0;
    }
     
    public void ensureCapacity(int minCapacity) {
        int oldCapacity = datas.length;
        if (minCapacity > oldCapacity) {
            int newCapacity = (oldCapacity * 3) / 2 + 1;
            if (newCapacity < minCapacity)
                newCapacity = minCapacity;
            datas = Arrays.copyOf(datas, newCapacity);
        }
    }
     
    private void RangeCheck(int index) {
        if (index >= size)
            throw new IndexOutOfBoundsException(
            "Index: "+index+", Size: "+size);
        }
}