Using numbers as package names in java

I've already checked the following posts:

https://docs.oracle.com/javase/specs/jls/se7/html/jls-6.html#jls-6.2

and SO post:

Is this a valid java package name?

and

What package naming convention do you use for personal / hobby projects in Java?

I tried to create a package like this:

package 01;
public class Test
{
// ...
}

      

        
        
        
      

    

When I compile, I get this:

I:\code>javac 01\Test.java
01\Test.java:1: error: <identifier> expected
package 01;
       ^
1 error

      

        
        
        
      

    

I am looking for the syntactic correctness of the name, not the convention.

Is there an oracle / SUN link that maps the syntax for a package, or follows the same rules as variable names in java? May be a reference in the Java language specification that package names follow the same rules as variable names.