Java Packages - refer to a class from a different package

Question

In the (default package) I have a class called "Bird" that has a method called "dialog".

I can create a class called Class1 within the same package, like this:

public class Class1
{
    public static void main(String[] args) 
    {
        Bird b = new Bird("Alexander",true,5);
        b.dialog("tweet!");
    }
}

This actually works and I actually get to see tweet! in the console.

My question is: what do I need to add in the code if Class1 is located in the package Fundamental (whereas the class Bird is located in the "default package")? I get an error: "Bird type not recognised" in this case. I should probably indicate the package somehow.

Side questions: 1. What is a classpath and how do you change it? I have seen this term vaguely used in the context of several package-related discussions, but none with clear examples as I just gave. 2. I have seen many times packages called xxx.bla.zzz - is this a standard? I only usually use a common name (not three separated by .) I understand a package is Java's replacement for namespaces in other languages. If there are several solutions solutions worth mentioning, I'd appreciate. Thank you!

Answer 1

You should never use the default package, it is not a good practice and you can't import classes from the default package. Always declare your package structure.

In the class Bird in the first line add:

package animals;

In the first line of your Class1.java write your package name

package foo;

import animals.Bird;

Note that for this to work the class Bird and the class Class1 should be respectively in the folder "animals" and the folder "foo"