第十七题：使用数组结构实现大小固定栈（Java）

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题目要求：

如标题

代码实现：

package com.isea.brush;

/**
 * 使用数组结构实现固定长度的栈结构
 * 实现思路：index位置表示的是如果要入栈，元素应该存放数据的位置
 */
public class ArrayStack {
    private Integer data[];
    private int index;

    public ArrayStack(int initalSize) {
        if (initalSize <= 0) {
            throw new IllegalArgumentException("The init is less than 0...");
        }
        data = new Integer[initalSize];
        index = 0;
    }

    public void push(int value) {
        if (index == data.length) {
            throw new IllegalArgumentException("The stack is full...");
        }
        data[index++] = value;
    }

    public int pop() {
        if (index == 0) {
            throw new IllegalArgumentException("The stack is empty...");
        }
        return data[--index];
    }

    public int peek() {
        if (index == 0) {
            throw new IllegalArgumentException("The stack is empty...");
        }
        return data[index - 1];
    }
}