LeetCode题解—实现一个栈

public class ArrayStack {
    // 数组
    private String[] items;  
    // 栈中已有元素个数
    private int count; 
    // 栈（数组）的大小
    private int n;           

    // 初始化数组
    public ArrayStack(int n) {
        this.items = new String[n];
        this.n = n;
        this.count = 0;
    }


    //返回栈顶元素
    public String peek() {
        String t = null;
        if (count > 0)
            t =  items[count-1];
        return t;
    }

    // 入栈
    public boolean push(String item) {
        //判断是否扩容栈
        expandCapacity(count + 1);
        System.out.println("count="+count+"n="+n);
        items[count] = item;
        count++;
        return true;
    }

    // 出栈
    public String pop() {
        if (count == 0) return null;
        String tmp = items[count-1];
        count--;
        return tmp;
    }

    // 扩大容量
    public void expandCapacity(int size) {
        if (size > n) {
            //每次扩容50%
            n = size * 3 / 2 + 1;
            items = Arrays.copyOf(items, n);
        }
    }
}