从单独的类文件访问公共静态类的状态 [英] Access public static class' state from a separate class file

问题描述

我在另一个公共类中有一个公共静态类，如下所示：

I have a public static class within another public class as follows:

public class Foo<A> {
public static class Bar<A>{
    A firstBar;
    Bar(A setBar){
        this.firstBar=setBar;
    }
   }

public final Bar<A> instanceBar;

public Foo(A actualValue) {
    instanceBar = new Bar<A>(actualValue);
}

public Bar<A> getBar() {
    return instanceBar;
}

我的目标是访问 instanceBar 来自不带get方法的单独类文件的状态，并且没有更改 firstBar 的可见性。我如何做到这一点？

My objective is to access instanceBar's state from a separate class file without a get method and without changing the visibility of firstBar. How do I accomplish this?

例如，以下说不可见。

public class RetrieveFirstBar {
        public static void main(String[] args) {
             Foo z = new Foo(5l);
             Foo.Bar<Long> z2 = z.getBar();
             long k = z2.firstBar; //not visible!
        }

}

推荐答案

我想你的意思是

class Foo<A>

因为你写的是A firstBar;您提供对变量的包访问权限：
http：// docs .oracle.com / javase / tutorial / java / javaOO / accesscontrol.html

Since you write "A firstBar;" you give package access to the variable: http://docs.oracle.com/javase/tutorial/java/javaOO/accesscontrol.html

如果你在同一个包中有RetrieveFirstBar，你就不会有可见性问题。但是，如果你想从任何地方访问它，你应该写

If you have the RetrieveFirstBar in the same package you will not have visibility problems. But, if you want to access it from everywhere you should write

public A firstBar;

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