java - 如何在不使用任何用户定义的类的情况下开发 Java 应用程序？

Question

是否可以创建任何只能使用内置类的应用程序？应用程序，如添加或其他基本操作

ex 内置类，如 class String{} class Object{}

Answer 1

I don't understand what you mean fully. If you mean an application that doesn't instantiate any non-standard classes, then yes of course, here:

public class MyApplication {
    public static void main(String[] args) {
        System.out.println("hello world");
    }
}

If you mean an application in which we don't have any non-standard classes at all, then no: you need to have a main() method in some class somewhere.

Answer 2

Well, yeah. All existing libraries either use built-in methods or use another library that does, or somewhere down the chain built in methods will be used.

All you would be doing is recreating functionality someone already built.

Answer 3

"Any" application no.."an" application yes

Answer 4

You will need to write the class that contains your main(), so strictly speaking, no. But apart from that, you can get quite a lot done with the standard JRE library.

Answer 5

JAVA 是一种面向对象的语言，因此在正常使用中您将定义类。但是，您可以在 JAVA 中进行纯函数式编程，而无需实例化任何用户定义的对象。但是每个函数都必须包含在一个类中，因此您需要至少定义一个包含应用程序逻辑的类。

 class MyOnlyClassThatIDontInstantiate{
      public static void main(String args[]){
           System.out.println("Hello world!");
           System.out.println("2 + 3 = "+addNumbers(2,3));
      }
      public static int addNumbers(int a, int b){
          return a+b;
      }
 }

以上是一个徒劳的应用程序，只使用函数式编程。没有类被实例化，但主要方法必须包含在一个类中。