One Public Class Per File

Feb 8, 2014

The compiler won't let me declare more than one class as "public". Am i correct in understanding that this is a java restriction ? This means i need to create a new file, for each public class that i want in a package ? The rest of the classes without access modifier will all be package-private. (Q has been asked before probably, but my search could not be narrowed).

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Non-Public Class In A Source File Doesn't Matching Its Name

Oct 20, 2014

I have a question about the following snippet concerning the steps the javac compiler follows to compile a program:

[...]at first, searching a class within a package is discussed if the latter doesn't contain a full package name[...]

It is a compile-time error if more than one class is found. (Classes must be unique, so the order of the import statements doesn't matter.)

The compiler goes one step further. It looks at the source files to see if the source is newer than the class file. If so, the source file is recompiled automatically. Recall that you can import only public classes from other packages. A source file can only contain one public class, and the names of the file and the public class must match. Therefore, the compiler can easily locate source files for public classes.

However, you can import nonpublic classes from the current package. These classes may be defined in source files with different names. If you import a class from the current package, the compiler searches all source files of the current package to see which one defines the class. I don't quite understand the red fragment. I wondered if the word "import" nonpublic classes from the current package weren't a synonym for the word "use", since why would we want to import a class from the same package when compiler searches the current package automatically anyway?

However I wanted to test nonpublic classes that are contained in source file which name doesn't match the class name:

NonpublicClass.java:

Java Code:

package com.work.company;
class NonpublicClass
{
public void description() {
System.out.println("Working!");
}
} mh_sh_highlight_all('java');

[Code] ....

Everything's fine when the source file names are the same as above. However, when I change NonpublicClass.java to a different name, there's an error "cannot find symbol" in:

Java Code: NonpublicClass v = new NonpublicClass(); mh_sh_highlight_all('java');

I noticed that the class file for NonpublicClass isn't even generated so that's probably the cause. If I change to the directory of the package the NonpublicClass is contained in and compile it directly, i.e. issue for example:

Java Code: javac NonpublicClass_different_name.java mh_sh_highlight_all('java');

Then a proper class file is generated with the class name, that is NonpublicClass.class, and afterwards I can compile the main program in Start.java.

So the question is what am I missing regarding the cited quote that reads:

If you import a class from the current package, the compiler searches all source files of the current package to see which one defines the class.

? Because adding such an import to CompanyClass.java:

import com.work.company.NonpublicClass;

didn't work either...