java实现栈的简单操作

public class stract {
    public static void main(String[] args) {
        MyStack stack = new MyStack(20);

        stack.push(10);
        stack.push(20);
        stack.push(30);

        System.out.println(stack);
        System.out.println(stack.peek());
        stack.pop();
        System.out.println(stack);
        stack.pop();
        System.out.println(stack);
    }
}

class MyStack {
    // 底层用数组实现
    private long[] arr;

    private int pop;

    public MyStack() {
        arr = new long[10];
        pop = -1;
    }

    public MyStack(int maxsize) {
        arr = new long[maxsize];
        pop = -1;
    }

    public void push(long data) { //入栈
        arr[++pop] = data;
    }

    public long pop() {//弹栈
        return arr[pop--];
    }

    public long peek() {//查看栈顶数据
        return arr[pop];
    }

    public String list() {//遍历数据
        String str = "";
        for (int i = 0; i <= pop; i++) {
            str += arr[i] + " ";
        }
        return str;
    }

    public String toString() {
        return list();
    }
}