[数据结构]-数组实现栈

package com.cn.jichu.day08;

public class Stack<E> {

    /**
     * 数组
     */
    private E[] data;
    /**
     * 当前容纳元素个数
     */
    private int size;
    /**
     * 指针
     */
    private int pointer;

    public Stack(int capacity) {
        data = (E[])new Object[capacity];
        size = capacity;
        pointer = 0;
    }

    public Stack() {
       this(10);
    }

    /**
     * 入栈
     * @param e
     */
    public void push(E e){
        if(pointer == size){
            throw  new IllegalArgumentException("大哥，栈要溢出来了");
        }

        data[pointer] = e;
        pointer ++;
    }

    /**
     * 出栈
     * @return
     */
    public E pop(){
        if(pointer==0){
            throw  new IllegalArgumentException("大哥，栈中无元素哟");
        }
        E e = data[pointer-1];
        data[pointer-1] = null;
        pointer --;
        return e;
    }

    /**
     * 获取栈顶元素
     * @return
     */
    public E peek(){
        if(pointer==0){
            throw  new IllegalArgumentException("大哥，栈中无元素哟");
        }
        E e = data[pointer-1];
        return e;
    }


    @Override
    public String toString(){
        StringBuilder stringBuilder = new StringBuilder();
        stringBuilder.append("Stack [");
        for(int i=0;i<data.length;i++){
           stringBuilder.append(data[i] + " ");
        }
        stringBuilder.append("]");
        return stringBuilder.toString();
    }


}