Why the name of the public class should be the name of the file as well

[Avinash Haridasu]

In Java,

When a file contains public class

public class Demo{
}

The code above should be saved with a file name Demo.java


Why it does not get compiled if the file name is not Demo.java ??
Is there any reason for that ??

[Stephan van Hulst]

Yes. This is so the compiler can easily find files when a class from outside the package refers to it. And not only the compiler: imagine how annoying it would be when you're looking for the source code of some class, so you can understand the implementation. You would have to open every file in the package to find the class, or write a program to look for it.

[Campbell Ritchie]

If you search, you will find many threads about the same question.