栈（Java实现）

package ch03;

public class MyStack {
    // 底层实现是一个数组
    private long[] arr;
    private int top;

    /**
     * 默认的构造方法
     */
    public MyStack() {
        arr = new long[10];
        top = -1;
    }

    /**
     * 带参数构造方法，参数为数组初始化大小
     */
    public MyStack(int maxsize) {
        arr = new long[maxsize];
        top = -1;
    }

    /**
     * 添加数据
     */
    public void push(int value) {
        arr[++top] = value;
    }

    /**
     * 移除数据
     */
    public long pop() {
        return arr[top--];
    }

    /**
     * 查看数据
     */
    public long peek() {
        return arr[top];
    }

    /**
     * 判断是否为空
     */
    public boolean isEmpty() {
        return top == -1;
    }

    /**
     * 判断是否满了
     */
    public boolean isFull() {
        return top == arr.length - 1;
    }
}

package ch03;

public class TestMyStack {
    public static void main(String[] args) {
        MyStack ms = new MyStack(4);
        ms.push(23);
        ms.push(12);
        ms.push(1);
        ms.push(90);
        System.out.println(ms.isEmpty());
        System.out.println(ms.isFull());
        
        System.out.println(ms.peek());
        System.out.println(ms.peek());
        
        while(!ms.isEmpty()) {
            System.out.print(ms.pop() + ",");
        }
        
        System.out.println(ms.isEmpty());
        System.out.println(ms.isFull());
    }
}