public interface Stack<E> {

    int getSize();
    boolean isEmpty();
    void push(E e);
    E pop();
    E peek();
}

public class Array<E> {

    private E[] data;
    private int size;  //大小

    // 构造函数 转入数组的容量capacity构造Array
    public Array(int capacity){
        data =(E[])new Object[capacity];
        size = 0    ;
    }

    // 无参的构造函数，默认数组的容量capacity = 10
    public Array(){
        this(10); //调用有参构造函数传入10设定初始大小
    }

    // 获取数组中元素个数
    public int getSize(){
        return size;
    }

    // 获取数组的容量
    public int getCapacity(){
        return data.length;
    }

    //返回数组是否为空
    public boolean isEmpty(){
        return size == 0;
    }

    // 向所有元素后添加一个新元素
    public void addLast(E e){

//         if(size == data.length) {
//             throw new IllegalArgumentException("AddLast failed. Array is full.");
//         }
//         data[size] = e;
//         size ++;
        add(size, e);
    }

    // 在所有元素前添加一个新元素
    public void addFirst(E e){
        add(0, e);
    }

    // 在第index个位置插入一个新元素e
    public void add(int index, E e){

        if(index < 0 || index > size ){
            throw new IllegalArgumentException("Add failed. Require index >=0 and index <= size.");
        }

        if(size == data.length) {
            resize(2 * data.length);
        }

        for(int i = size - 1 ; i >= index ; i  --){
            data[i + 1]=data[i];
        }
        data[index] = e;
        size ++;
    }

    // 获取index索引位置的元素
    public E get(int index){
        if(index < 0 || index >= size)
            throw new IllegalArgumentException("Get failed. Index is illegal.");
        return data[index];
    }

    public E getLast(){
        return get(size - 1);
    }

    public E getFirst(){
        return get(0);
    }

    // 修改index索引位置的元素为e
    public void set(int index, E e){
        if(index < 0 || index >= size)
            throw new IllegalArgumentException("set failed. Index is illegal.");
        data[index] = e;

    }

    // 查找数组中是否有元素e
    public boolean contains(E e){
        for(int i = 0 ; i < size ; i++)
        {
            if(data[i].equals(e))
                return true;
        }
        return false;
    }

    // 查找数组中元素e所在的索引，如果不存在元素e，则返回-1
    public int find(E e){
        for(int i = 0 ; i < size ; i++)
        {
            if(data[i].equals(e))
                return i;
        }
        return -1;
    }

    // 从数组中删除index位置的元素，返回删除的元素
    public E remove(int index){
        if(index < 0 || index >= size)
        {
            throw new IllegalArgumentException("Remove failed. Index is illegal.");
        }
        E ret = data[index];
        for(int i = index + 1 ; i < size ; i ++)
        {
            data[i-1] = data[i];
        }
        size --;
        data[size] = null; //让他自动回收 非必须写  loitering objects ！= memory leak

        if(size == data.length / 4 && data.length / 2 != 0)
            resize(data.length / 2);
        return ret;
    }

    // 从数组中删除第一个元素，返回删除的元素
    public E removeFirst(){
        return remove(0);
    }

    // 从数组中删除最后一个元素，返回删除的元素
    public E removeLast(){
        return remove(size-1);
    }

    // 从数组中删除元素e
    public void removeElement(E e){
        int index = find(e);
        if(index != -1)
            remove(index);
    }


    //system.out.print()所输出的类型toString覆盖
    @Override
    public String toString(){

        StringBuilder res = new StringBuilder();
        res.append(String.format("Array: size = %d, capacity = %d \n", size, data.length));
        res.append('[');
        for(int i = 0 ; i < size ; i ++){
            res.append(data[i]);
            if(i != size - 1)
                res.append(", ");
        }
        res.append(']');
        return res.toString();
    }

    private void resize(int newCapacity){
        E[] newData = (E[])new Object[newCapacity];
        for(int i = 0 ; i < size ; i ++)
            newData[i] = data[i];
        data = newData;
    }
}

public class ArrayStack<E> implements Stack<E> {

    Array<E> array; //动态数组

    public ArrayStack(int capacity){
        array = new Array<>(capacity);
    }

    public ArrayStack(){
        array = new Array<>();
    }

    @Override
    public int getSize(){
        return array.getSize();
    }

    @Override
    public boolean isEmpty(){
        return array.isEmpty();
    }

    public int getCapacity(){
        return array.getCapacity();
    }

    @Override
    public void push(E e){
        array.addLast(e);
    }

    @Override
    public E pop(){
        return array.removeLast();
    }

    @Override
    public E peek(){
        return array.getLast();
    }

    @Override
    public String toString(){
        StringBuilder res = new StringBuilder();
        res.append("Stack: ");
        res.append('[');
        for (int i = 0 ; i < array.getSize() ; i ++){
            res.append(array.get(i));
            if(i != array.getSize()-1)
                res.append(", ");
        }
        res.append("] top");
        return res.toString();
    }
}

public class Main {

    public static void main(String[] args){

       ArrayStack<Integer> stack = new ArrayStack<>();

       for(int i = 0 ; i < 5 ; i++){
           stack.push(i);
           System.out.println(stack);
       }

       stack.pop();
       System.out.println(stack);
    }
}