.java file path to class name

Question

What's the most efficient way of getting the class(es) created on a .java file? I have the .java file path and I need to get the class full name.

I can only remember:

1. Compile it with JavaCompiler
2. Using the file text to parse it with Eclipse ASTParser (or another)
3. Infer the class name through part of the file path, but I don't know if this works for every cases
4. Somehow, use a tool like javap (dind't really thought about this one)

EDIT

I have this file, located at C:\myfolder\MyClass.java (let's ignore package and folder association conventions):

package mypackage.mysubpackage;

public class MyClass 
{
    // my class implementation here

    public class MyInnerClass 
    {
        // my inner class implementation here
    } 
}

The full name of the classes declared in this file are:

1. mypackage.mysubpackage.MyClass
2. mypackage.mysubpackage.MyClass.MyInnerClass (I don't know if this one it's correct, but let's pretend it is)

How can I get those class when I only have the .java file path (C:\myfolder\MyClass.java) ?

Answer 1

The only way to reliably obtain the names of the classes (mind that it may also define interfaces) files a .java file declares would be to really parse the java language contained in that file.

And even then you will need to know which compiler will be/has been used to compile the .java file, as a java compiler could use any naming convention it likes for anonymous classes (the Oracle compiler uses $1, $2..., but there is no strict need to mimic that behavior).

Considering these obstacles I believe its very hard to do from the .java files contents and simply impossible with the .java files path alone.

Answer 2

The most effective way is Class.forName().getName()

Answer 3

I have the .java file path and I need to get the class full name.

Which means, you know the path of .java file and you want the class name of each class file.

class Filter {

public static void main(String[] a) {
    Filter f = new Filter();
    String dirName = "D:\\Yourfolder\\";  // assuming your java file are located in D:\Yourfolder\
    f.finder(dirName);  // call the method for listing all the class file
}

public File[] finder(String dirName) {

    File dir = new File(dirName);

    return dir.listFiles(new FilenameFilter() {

        public boolean accept(File dir, String filename) {
            if(filename.endsWith(".class"))
            {
            System.out.println(filename);
            }
            return filename.endsWith(".class");

        }
    });

}

}

Replace dirName with your .java directory path.

Answer 4

One approach is to scan the directory tree where your Java source files are located, and for each file ending in ".java", you take its full folder path as a String and convert each dir separator to a '.' character. This will give you the fully qualified class name (FQCN). For example, if the path is: com\foo\fee\Foo.java, that becomes com.foo.fee.Foo.

Of course, this does not give you inner or nested classes and other advanced things, but these are created when you compile.

I have seen this kind of directory scanning in many frameworks, even Spring.

I am working on this in Groovy, so far I have:

File file = new File(rootSourcePath)

file.eachFileRecurse(FILES){
    def path =it.getAbsolutePath()
    println path

    if(path.endsWith(".java")){
           // to do the conversion here
    }
}

Hope this interpreted your question correctly.

Answer 5

To get the name of the class file Try this

      void printClassName(String classname) 


        {

          System.out.println("The class name " + classname +" is " + classname.getClass().getName());

        }