學習筆記-用數組寫出棧的過程

小白一枚，勿噴。下邊上代碼
棧的過程先入後出，後入先出。

public class ArryStack {
    public static void main(String[] args) {
        ArrayStack as = new ArrayStack(4);
        String key = "";
        boolean flag = true;
        Scanner sc = new Scanner(System.in);
        while (flag){
            System.out.println("show: 顯示數據");
            System.out.println("exit: 退出");
            System.out.println("push: 添加");
            System.out.println("pop: 取出");
            System.out.println("請輸入你的選擇");
            key = sc.next();
            switch (key){
                case "show":
                    as.list();
                    break;
                case "exit":
                    flag = false;
                case "pop":
                    try {
                        int value = as.pop();
                        System.out.printf("出棧的數據是%d\n", value);
                    }catch (Exception e){
                        System.out.println(e.getMessage());
                    }
                    break;
                case "push":
                    System.out.println("請輸入你要添加的數據");
                    int value = Integer.parseInt(sc.next());
                    as.push(value);
                    break;
                default:
                    break;
            }
        }

    }
}


class ArrayStack{
    private int maxSize;
    private int[] stack;
    private int top = -1;

    //構造器
    public ArrayStack(int maxSize){
        this.maxSize = maxSize;
        stack = new int[this.maxSize];
    }
    //棧滿
    public boolean isFull(){
        return top == maxSize - 1;
    }
    //棧空
    public boolean isEmpty(){
        return top == -1;
    }
    //入棧-push
    public void push(int value){
        if (isFull()){
            System.out.println("棧滿");
            return;
        }
        top++;
        stack[top] = value;
    }
    //出棧-pop
    public int pop(){
        if (isEmpty()){
            throw new RuntimeException("棧空");
        }
        int value = stack[top];
        top--;
        return value;
    }
    //顯示棧的情況
    public void list(){
        if (isEmpty()){
            System.out.println("棧空");
            return;
        }
        for (int i = top; i >= 0; i--){
            System.out.printf("stack[%d]的數據爲%d\n", i, stack[i]);
        }
    }
}