package com.jalja.org.arith;

public class MyStack<E>{

    private Object [] arr;//存储

    private int index;//栈元素实际入栈索引

    private int maxSize;//栈的最大空间

    private MyStack(int maxSize) {

        this.arr=new Object[maxSize];

        this.index=0;

        this.maxSize=maxSize;

    }

    //入栈

    public void push(E e) {

        if(isFull()) {

            throw new RuntimeException("myStack  is full ");

        }

        arr[index++]=e;

    }

    //出栈

    public E pop() {

        if(isNull()) {

            throw new RuntimeException("myStack is null ");

        }

        E e=(E)arr[--index];

        return e;

    }

    //访问栈顶元素

    public E peek() {

        return (E)arr[index-1];

    }

    //栈是否为空

    public boolean isNull() {

        return this.index <= 0;

    }

    //栈是否满了

    public boolean isFull() {

        return index>=maxSize;

    }

    public static void main(String[] args) {

        MyStack<String> myStack=new MyStack(3);

        myStack.push("A0");

        myStack.push("A1");

        myStack.push("A2");

        System.out.println(myStack.peek());

        while(!myStack.isNull()) {

            System.out.println(myStack.pop());

        }

    }

}