Answer:
No. Any order would work.
No. Any order would work.
A better way to organize the program is to put each class and interface into its own file.
If this is done, each class can be made public.
//File: Taxable.java
interface Taxable
{
}
//File: Goods.java
public class Goods
{
}
//File: Food.java
public class Food extends Goods
{
}
//File: Toy.java
public class Toy extends Goods implements Taxable
{
}
//File: Book.java
public class Book extends Goods implements Taxable
{
}
//File: Store.java
public class Store
{
}
Compile and run in the usual way.
The Java compiler looks for and compiles all the files it needs to compile Store.java.
The interface, also, compiles into a separate file, Taxable.class
C:\Temp>javac Store.java
C:\Temp>java Store
item: bubble bath price: 1.4
item: ox tails price: 4.45
calories: 1500.0
item: Legos price: 54.45
minimum age: 8
Tax is: 3.267
item: Emma price: 24.95
author: Austen
Tax is: 1.4969999999999999
C:\Temp>dir
08/22/2014 07:52 AM 811 Book.class
08/22/2014 07:47 AM 347 Book.java
08/22/2014 07:53 AM 708 Food.class
08/22/2014 07:52 AM 265 Food.java
08/22/2014 07:52 AM 750 Goods.class
08/22/2014 07:46 AM 355 Goods.java
08/22/2014 07:53 AM 1,157 Store.class
08/22/2014 07:44 AM 504 Store.java
08/22/2014 07:52 AM 179 Taxable.class
08/22/2014 07:50 AM 200 Taxable.java
08/22/2014 07:52 AM 825 Toy.class
08/22/2014 07:52 AM 443 Toy.java
12 File(s) 6,544 bytes
C:\Temp>