堆栈-未经检查/不安全的操作 [英] Stack - unchecked/unsafe operations

问题描述

因此，我尝试在此处运行此简单程序：

So I'm trying to run this simple program here:

import java.util.*;

class StackDemo
{
    public static void main(String[] args) {
        Stack s = new Stack();
        s.push(5);
        s.push("dog");
        System.out.print(s);
    }
}

StackDemo.java 使用未经检查或不安全的操作。
注意：有关详细信息，请使用 -Xlint：unchecked 重新编译。
处理完成。

StackDemo.java uses unchecked or unsafe operations. Note: Recompile with -Xlint:unchecked for details. Process completed.

它显示预期结果，即 [5，dog] 但我不明白构建输出窗口中的消息。
这里可能有什么问题？

It displays the expected result, which is "[5, dog]" but I don't understand that message on the Build Output window. What could possibly be wrong here?

推荐答案

堆栈是一个通用类，您可以根据需要使用它来存储特定类型的对象（例如， Stack< String> 将用于存储字符串）。使用裸类而没有类型说明符通常被认为是一种不好的做法，因为您会丢失集合的类型安全性。

Stack is a generic class, which you can use, if you wish, to store objects of a specific type (e.g., Stack<String> would be used to store strings). Using bare classes, without a type specifier is usually considered a bad practice, as you're losing the type safety of the collection.

如果确实存在用例，想要将 5 和 dog 都存储在堆栈中，则应使用最常见的堆栈定义堆栈两者之间的分母- Object ：

If there is indeed a usecase where you'd like to store both 5 and "dog" in your stack, you should define your stack with the greatest common denominator between the two - Object:

Stack<Object> s = new Stack<>();

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