Java单文件用于外部类

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英文:

Java Single File for External Classes

问题

我认为Java的做法是将外部类放在单独的文件中。因此，我最终的目录结构如下所示：

  1. /main/main.java
  2. /main/libs/class01.java
  3. /main/libs/class02.java
  4. /main/libs/class03.java

虽然这样做也可以，但其中一些类真的非常简单，例如，如果所有的类都只是：

  1. package libs;
  2. import java.util.*;
  4. public class class01 {
  5.     public Integer idno;
  6.     public String name;
  8.     public class01() {
  9.         idno = 1;
  10.         name = "First";
  11.     }
  12. }

那么单独的文件似乎有点过多。我想知道是否有一种方法将它们合并到单个文件中，类似于在.NET C#中使用命名空间的方式，如下所示：

  1. using System;
  2. using System.Data;
  4. namespace allClasses {
  6.     public class class01 {
  8.         public Integer idno;
  9.         public String name;
  11.         public class01() {
  12.             idno = 1;
  13.             name = "First";
  14.         }
  15.     }
  17.     public class class02 {
  19.         public Integer idno;
  20.         public String name;
  22.         public class02() {
  23.             idno = 2;
  24.             name = "Second";
  25.         }
  26.     }
  28.     public class class03 {
  30.         public Integer idno;
  31.         public String name;
  33.         public class03() {
  34.             idno = 2;
  35.             name = "Third";
  36.         }
  37.     }
  38. }

我可以在主程序中使用它们，就好像它们是分开的一样：

  1. using System;
  3. using allClasses;
  5. namespace main_module {
  7.     class main {
  9.         static void Main(string[] args) {
  11.             class01 newClass01 = new class01();
  12.             class02 newClass02 = new class02();
  13.             class03 newClass03 = new class03();
  14.         }
  15.     }
  16. }

对于比较两者，我感到抱歉，只是因为.NET C#是我能够展示我想要实现的内容的最佳示例。我还不知道如何在Java中做到这一点，非常感谢您提供指导。

英文:

I believe the Java way is to keep external classes in separate files. So I've ended up with a directory structure like the following

  1. /main/main.java
  2. /main/libs/class01.java
  3. /main/libs/class02.java
  4. /main/libs/class03.java

Which would be fine but some of the classes are really puny little things, for example if all the classes were just

  1. package libs;
  2. import java.util.*;
  3. public class class01 {
  5.     public Integer idno;
  6.     public String name;
  8.     public class01() {}
  9.         idno = 1;
  10.         name = "First";
  11.     }
  13. }

Then separate files seem like they could get a bit excessive. I'm wondering if there is a way to combine them into a single file similar to the way that you can do in .Net C# with namespaces like the following

  1. using System;
  2. using System.Data;
  4. namespace allClasses {
  6.     public class class01 {
  8.         public Integer idno;
  9.         public String name;
  11.         public class01() {}
  12.             idno = 1;
  13.             name = "First";
  14.         }
  16.     }
  18.     public class class02 {
  20.         public Integer idno;
  21.         public String name;
  23.         public class02() {}
  24.             idno = 2;
  25.             name = "Second";
  26.         }
  28.     }
  30.     public class class03 {
  32.         public Integer idno;
  33.         public String name;
  35.         public class03() {}
  36.             idno = 2;
  37.             name = "Third";
  38.         }
  40.     }
  42. }

Which I can use in my main as if they were all separate

  1. using System;
  3. using allClasses;
  5. namespace main_module {
  7.     class main {
  9.         static void Main(string[] args) {
  11.             class01 newClass01 = new class01();
  12.             class02 newClass02 = new class02();
  13.             class03 newClass03 = new class03();
  15.         }
  17.     }
  19. }

I'm sorry for comparing the two it's just that .Net C# is the best example I can show of what I am trying to achieve. I don't know a way of doing this yet in Java, some guidance would be very much appreciated

答案1

得分: 1

你可以将它们声明为另一个公共类内部的 public static class。
例如：

  1. public class Util {
  2.   public static class A {}
  3.   public static class B {}
  4. }

然后在主类中可以这样引用它们：

  1. new Util.A();

这样可以将源代码合并到一个单独的类中，但正如 @oleg-cherednik 提到的，编译后将会生成几个独立的类文件。

英文:

You can declare them as public static class within another public class.
E.g.

  1. public class Util {
  2.   public static class A {}
  3.   public static class B {}
  4. }

Then in your main class you can reference them as:

  1. new Util.A();

This will help you combine source code into a single class, but as @oleg-cherednik mentioned, when compiled there will be several separate class files.

huangapple
  • 本文由 发表于 2020年9月13日 18:42:00
  • 转载请务必保留本文链接：https://go.coder-hub.com/63869805.html
  • class
  • java
  • project-structure
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