hello-algo/codes/java/chapter_stack_and_queue/array_stack.java

/*
 * File: array_stack.java
 * Created Time: 2022-11-25
 * Author: Krahets (krahets@163.com)
 */

package chapter_stack_and_queue;

import java.util.*;

/* 基于数组实现的栈 */
class ArrayStack {
    private ArrayList<Integer> stack;
    public ArrayStack() {
        // 初始化列表（动态数组）
        stack = new ArrayList<>();
    }

    /* 获取栈的长度 */
    public int size() {
        return stack.size();
    }

    /* 判断栈是否为空 */
    public boolean isEmpty() {
        return size() == 0;
    }

    /* 入栈 */
    public void push(int num) {
        stack.add(num);
    }

    /* 出栈 */
    public int pop() {
        if (isEmpty())
            throw new EmptyStackException();
        return stack.remove(size() - 1);
    }

    /* 访问栈顶元素 */
    public int peek() {
        if (isEmpty())
            throw new EmptyStackException();
        return stack.get(size() - 1);
    }

    /* 访问索引 index 处元素 */
    public int get(int index) {
        if (index >= size())
            throw new IndexOutOfBoundsException();
        return stack.get(index);
    }

    /* 将 List 转化为 Array 并返回 */
    public Object[] toArray() {
        return stack.toArray();
    }
}

public class array_stack {
    public static void main(String[] args) {
        /* 初始化栈 */
        ArrayStack stack = new ArrayStack();

        /* 元素入栈 */
        stack.push(1);
        stack.push(3);
        stack.push(2);
        stack.push(5);
        stack.push(4);
        System.out.println("栈 stack = " + Arrays.toString(stack.toArray()));

        /* 访问栈顶元素 */
        int peek = stack.peek();
        System.out.println("栈顶元素 peek = " + peek);

        /* 访问索引 index 处元素 */
        int num = stack.get(3);
        System.out.println("栈索引 3 处的元素为 num = " + num);

        /* 元素出栈 */
        int pop = stack.pop();
        System.out.println("出栈元素 pop = " + pop + "，出栈后 stack = " + Arrays.toString(stack.toArray()));

        /* 获取栈的长度 */
        int size = stack.size();
        System.out.println("栈的长度 size = " + size);

        /* 判断是否为空 */
        boolean isEmpty = stack.isEmpty();
        System.out.println("栈是否为空 = " + isEmpty);
    }
}