访问其他类中的变量（Java） [英] Accessing variables in other classes (Java)

问题描述

以下程序为什么不返回 0 ，因为我正在从新A（）访问 p ，而该A（）没有主要打电话吗？

Why doesn't the following program return 0, since I am accessing p from a new A(), which has not had main called on it?

 public class A {

         public static int p = 0;

         public static void main(String[] args) {

                p = Integer.parseInt(args[0]);
                new B().go();

            }

        }


       class B {
            public void go() {
                System.out.println(new A().p);
            }
        }

推荐答案

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可能您将 p 设为静态，然后进行了更改。现在编写的方式无法编译。

Probably you had p as static and than you change it. The way it is written now, doesn't compile.

$ javac A.java 
A.java:7: non-static variable p cannot be referenced from a static context
            p = Integer.parseInt(args[0]);
            ^
1 error

编辑

现在，您已更正代码，答案为：

Now that you have corrected your code the answer is:

该程序不会打印 0 ，因为您看到的是在第7行中分配的值。在这种情况下， p

This program doesn't print 0 because what you see is the value assigned in line 7. In this case p is a class variable.

 p = Integer.parseInt(args[0]);

所以当您执行时：

 System.out.println(new A().p);

您期望看到 0 认为新A将拥有自己的 p 副本，但并非如此。

And you expect to see 0 thinking the "new A" will have it own copy of p but is not the case.

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