为什么类编译为.class但接口不编译为.interface

Question

是否有任何具体原因导致接口未编译成编译成.interface文件的MyInterface.java？但是任何类都被编译成.class文件。

Answer 1

因为要点是指示文件是Java字节代码 （而.class是为其选择的扩展名），而不是特定的语言结构。

Answer 2

The physical representation of the byte-code on the file system doesn't matter.

It's the logical realization (whether class or interface) that matters.

Answer 3

Java treats interfaces almost like classes, eg they share the same namespace (you can't have an interface that has the same name as a class) and a compiled interface is almost identical to a compiled abstract class.

So it would not make any sense to store them in a different format or with a different file extension. On the contrary, this would make many things harder. For example, when you load a class or interface by name (Class.forName("my.class.name")) Java does not know whether it is a class or an interface. If there would be two different extensions, Java would have try to find a file "my/class/name.class" and then "my/class/name.interface", instead of only trying the first one.

Answer 4

That's the way the language designers decided.

It makes sense in several ways:

• .class files are a byproduct that you don't normally see or manipulate by hand.
• The less different extensions a program uses, the easier it is to maintain.
• In many cases, there's no distinction in the code between a class and an interface, so it's logical that the binary files look alike.

Frankly, I can't think of a good reason to have different extensions for compiled classes and interfaces. Why would it be important to distinguish between them?

Answer 5

In java, you have source files, called .java and binaries called .class. Its just a choice of naming.

Also for java classes and interface's don't differ that much (a class just contains a lot of extra information like method bodies).

Answer 6

It is just a choice they made. I wouldn't bother about it. It is a binary file anyway. One way to think is "Even it is an interface it is still in a file.java".