数组实现栈

package com.yudaodata.protocol809.task;


import java.util.Arrays;
import java.util.EmptyStackException;

public class ArrayStack<T> {
    private Object[] elements = new Object[16]; //数组大小默认16
    private int count; //1.-1后指向栈内末尾的元素 2.统计栈内元素的数量

    public void push(T e) {
        //数组扩容
        if (count == elements.length) {
            elements = Arrays.copyOf(elements, 2 * count + 1);
        }
        elements[count++] = e;
    }

    public T pop() {
        if (count == 0) {
            throw new EmptyStackException();
        }
        T o = (T) elements[--count];
        elements[count] = null; //防止内存泄漏
        return o;
    }

    public static void main(String[] args) {
        ArrayStack<Integer> arrayStack = new ArrayStack<>();
        arrayStack.push(1);
        arrayStack.push(2);
        arrayStack.push(3);
        System.out.println(arrayStack.pop()); //2
        System.out.println(arrayStack.pop()); //1
        System.out.println(arrayStack.pop()); //1
    }

}