数组实现栈_用数组实现一个栈

import java.util.Arrays;

/**
 * @author roger
 * @create 2021-06-28 10:47
 */
public class MyStack {
    private int[] storage; // 存放栈中元素的数组
    private int capacity; // 栈的容量
    private int count; // 栈中元素的数量
    public static final int GROW_FACTOR = 2;

    public MyStack() {
        this.capacity = 8;
        this.storage = new int[8];
        this.count = 0;
    }

    public MyStack(int initialcapacity) {
        if (initialcapacity < 1) {
            throw new IllegalArgumentException("Capacity too small.");
        }
        this.capacity = initialcapacity;
        this.storage = new int[initialcapacity];
        this.count = 0;
    }

    // 入栈
    public void push(int value) {
        if (count == capacity) {
            ensureCapacity();
        }
        storage[count++] = value;
    }

    // 确保容量大小
    private void ensureCapacity() {
        int newCapacity = capacity * GROW_FACTOR;
        storage = Arrays.copyOf(storage, newCapacity);
        capacity = newCapacity;
    }

    // 返回栈顶元素并出栈
    private int pop() {
        if (count == 0) {
            throw new IllegalArgumentException("Stack is empty.");
        }
        count--;
        return storage[count];
    }

    // 返回栈顶元素不出栈
    private int peek() {
        if (count == 0) {
            throw new IllegalArgumentException("Stack is empty.");
        }
        return storage[count - 1];
    }

    // 判断栈是否为空
    private boolean isEmpty() {
        return count == 0;
    }

    // 返回栈中元素的个数
    private int size() {
        return count;
    }

    public static void main(String[] args) {
        MyStack myStack = new MyStack(3);
        myStack.push(7);
        myStack.push(6);
        myStack.push(5);
        myStack.push(3);
        myStack.push(4);
        myStack.push(2);
        myStack.push(1);
        myStack.push(10);
        System.out.println(myStack.peek());//8
        System.out.println(myStack.size());//8
        for (int i = 0; i < 8; i++) {
            System.out.println(myStack.pop());
        }
        System.out.println(myStack.isEmpty());//true
        myStack.pop();//报错：java.lang.IllegalArgumentException: Stack is empty.
    }
}

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