java Package declarations

Each file may have a package declaration which precedes all non-comment code. The package name must be the same as the enclosing directory.

Default package. If a package declaration is omitted, all classes in that directory are said to belong to the "default" package.

Here are two files in the packagetest directory.

package packagetest;

class ClassA {
   public static void main(String[] args) {
       ClassB.greet();
   }
}

and

package packagetest;  // Same as in previous file.

class ClassB {
   static void greet() {
       System.out.println("Hi");
   }
}

Note that these source files must be named ClassA.java and ClassB.java (case matters) and they must be in a directory named packagetest.