javax.tool.JavaFileManager.getFileForInput(): spec for packageName parameter isn't actual

The spec states:
packageName - a package name as defined in the Java Language Specification

It seems to be wrong.

Note: I think packageName parameter for getFileForInput method is superfluous because any file (especially non-JavaFileObject) can be fully specified via relativeName. Now the same file can be specified using different sets of parameters.

What about non-letter characters in file path?

test:
----------------------
import javax.tools.*;
import java.io.File;
import java.net.URI;
import java.util.Collections;

public class test4 {
    static public void main(String[] args){
        URI uri = new File(".").toURI().normalize();
        File dir = new File( uri );

        StandardJavaFileManager sfm =
            ToolProvider.getSystemJavaCompilerTool().
                getStandardFileManager( new DiagnosticCollector<JavaFileObject>() );

        JavaFileManager.Location location = StandardJavaFileManager.StandardLocation.SOURCE_PATH;
        sfm.setLocation( location, Collections.singleton(dir) );

        try {
            String packageName = "tra-la-la/..";
            FileObject fo = sfm.getFileForInput( location, packageName, URI.create("test4.java") );
            if( fo != null )
                System.out.println( "package name = " + packageName );
        } catch( java.io.IOException x ){
            x.printStackTrace(System.out);
        }
    }
}
----------------------
result:
----------------------
package name = tra-la-la/..
Is it possible to specify results of this method more precisely in exceptions part?
For example, to remove 'may be thrown'.