Java引用同一目录中的类 [英] Java referencing a class in the same directory

问题描述

我用Java创建了一个 Pair 类(类似于c ++对)，但在从另一个Java文件中引用它时遇到了麻烦.我正在处理Java文件，我们将其称为 fileA ，与 Pair.class在同一目录中.另外，我在两个文件的顶部都写了 package当前目录.

I created a Pair class in Java (similar to the c++ pair) and am having trouble referencing it from a different java file. I am working inside a Java file, let's call it fileA in the same directory as Pair.class. Additionally, I have written package current-directory at the top of both files.

但是，当我尝试 javac fileA 时，我所有的错误都是找不到符号，并且小箭头指向了我的自定义 Pair 类型.

However, when I try javac fileA all my errors are cannot find symbol and the little arrow points to my custom Pair type.

如何让Java编译器在 fileA 中看到 Pair.class ?

How do I get the java compiler to see Pair.class inside of fileA?

感谢所有帮助

推荐答案

Java由一些基本约定驱动，包括目录结构遵循包结构，并且java文件以它们定义的类命名.

Java is driven by some basic conventions, including that directory structure follows package structure, and java files are named after the classes they define.

您应该像这样将fileA定义为fileA.java内部的类:

You should have defined fileA as a class inside of fileA.java like so:

public class fileA {
    public static void main(String[] args) {
        Pair p = new Pair(0, 1);
        System.out.println("a is "+p.a+" and b is "+p.b);
    }
}

和相应的Pair类:

public class Pair {
    public final int a;
    public final int b;
    public Pair(int a, int b) {
        this.a = a;
        this.b = b;
    }
}

如果要从与两个java文件相同的目录中调用javac，则不应在顶部声明程序包，因为它们位于默认程序包"中.因此，上面的方法应该起作用.

If you are calling javac from within the same directory as both java files, you should not declare a package at the top, as they are within the 'default package'. As such, the above should work.

使用默认程序包提供了一些便利，但也提供了一些我将不详述的限制，但是现在您已经知道了默认程序包，可以查找它了.我建议使用软件包名称，就像添加名称一样简单:

Using the default package provides some convenience but also some restrictions which I won't elaborate on, but now that you know about the default package you can look it up. I recommend using package names, which is as simple as adding, as you did, something like:

package kugathasan;

每个文件开头的

.如果这样做，则应将两个文件都放在一个名为kugathasan的目录中，并从包含kugathasan的目录中调用javac.

at the beginning of each file. If you do this though, you should put both files in a directory called kugathasan and call javac from the directory containing kugathasan.

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