point-of-sale scanning API（java）

Andrew Liu

Structure

instruction

Used strategy design pattern to calculate the price. right now I used Singleton for service class. because it is only execute by one customer right now. and it is mulithread-safe.

In the future, for extensive purpose, we can have a HashMap<User, Service> to process the request for mulitple customers.

And for the state transition of App class, it also could be implemented by state design pattern

Why use strategy design pattern?

1.GetFreeFirstStrategy -> Consider the buy 1 get 1 free first when calculate the total price
2.VolumeSaleFirstStrategy -> Consider the volume sale first when calculate the total price

case 1:

A |$2.0 each or 4 for $7.0
B |$10.0 buy 1 B get 1 A free

scan("AAAAABB") -> 5As 2Bs

1.GetFreeFirstStrategy -> the total price = (2 * 3 + 10 * 2) *(1 + tax) = 26 * 1.1 = 28.6
2.VolumeSaleFirstStrategy -> the total price = (7 + 10 * 2) * (1 + tax) = 27 * 1.1 = 29.7
So, in this case, the correct total price is 28.6(GetFreeFirstStrategy)

case 2:

A |$1.0 each or 6 for $5.0
B |$10.0 buy 1 B get 1 A free

scan("AAAAAAABB") -> 7As 2Bs

1.GetFreeFirstStrategy -> the total price = (1 * 5 + 10 * 2) *(1 + tax) = 25 * 1.1 = 27.5
2.VolumeSaleFirstStrategy -> the total price = (5 + 10 * 2) * (1 + tax) = 25 * 1.1 = 27.5
So, in this case, the correct total price is 27.5(both these 2 strategies right)

case 3:

A |$1.0 each or 7 for $5.0
B |$2.0 buy 1 B get 1 A free

scan("AAAAAAAABB") -> 8As 2Bs

1.GetFreeFirstStrategy -> the total price = (1 * 6 + 10 * 2) *(1 + tax) = 26 * 1.1 = 28.6
2.VolumeSaleFirstStrategy -> the total price = (5 + 10 * 2) * (1 + tax) = 25 * 1.1 = 27.5
So, in this case, the correct total price is 27.5(VolumeSaleFirstStrategy)

1.Run this code

$ javac src/*.java
$ cd src/
$ java Main

When the application starts, it will print the main with price.
continue -> input product code -> input 'r' to get the total price
set -> set the Unit Price, Volume Size(optional) or Volume Price(optional).
exit -> terminate this process

Product Code | Price
A                        |$2.0 each or 4 for $7.0
B                        |$10.0 each
C                        |$1.25 each or 6 for $6.0
D                        |$0.15 each or 4 for $7.0
E                        |$2.0 each AND if buy one B get one E
Please enter 'continue' to continue with current pricing or 'set' to add new pricing
Please enter 'exit' to exit this program

2.Continuing with exiting pricing

continue with existing price enter continue continue -> input product code -> input 'r' to get the total price

>>>continue
Enter the products code you want to buy in a single line then Enter 'r' to get the total price(no space)
>>>ABCDE
Enter the products code you want to buy in a single line then Enter 'r' to get the total price(no space)
>>>r
The total price is $14.74
Please enter 'continue' to continue with current pricing or 'set' to add new pricing
Please enter 'exit' to exit this program
>>>

before enter 'r', you can scan as much as you want to the cart

Enter the products code you want to buy in a single line then Enter 'r' to get the total price(no space)
>>>A
Enter the products code you want to buy in a single line then Enter 'r' to get the total price(no space)
>>>B
Enter the products code you want to buy in a single line then Enter 'r' to get the total price(no space)
>>>C
Enter the products code you want to buy in a single line then Enter 'r' to get the total price(no space)
>>>r
The total price is $14.575
Please enter 'continue' to continue with current pricing or 'set' to add new pricing
Please enter 'exit' to exit this program

if the cart is empty, you don't need to check out

Please enter 'continue' to continue with current pricing or 'set' to add new pricing
Please enter 'exit' to exit this program
>>>continue
Enter the products code you want to buy in a single line then Enter 'r' to get the total price(no space)
>>>r
no select
Invalid order!!! do it again!

if you entered unexist product code(it will be double checked in service class)

>>>ABCDF
Enter the products code you want to buy in a single line then Enter 'r' to get the total price(no space)
>>>Invalid product code(Only A - E)

the checkout will not success when the stock is not enough

Enter the products code you want to buy in a single line then Enter 'r' to get the total price(no space)
>>>AAA
Enter the products code you want to buy in a single line then Enter 'r' to get the total price(no space)
>>>r
Stock of A is  not enough for this order!   Stock for this product :2

3.Continuing with another order

Please enter 'continue' to continue with current pricing or 'set' to add new pricing
Please enter 'exit' to exit this program
>>>continue
Enter the products code you want to buy in a single line then Enter 'r' to get the total price(no space)
>>>

4. update a new price

set -> set the Unit Price, Volume Size(optional) or Volume Price(optional).

>>>set
Enter new Pricing in the format <Product Code> <Per Unit Price> <Volume Size(optional)> <Volume Price(optional)>, split with one space
>>>

For example, enter A 9.9 if the code executed sucessed, the menu will show again to indict the next step.

>>>A 9.9
Product Code | Price
A                        |$9.9 each or 4 for $7.0
B                        |$10.0 each
C                        |$1.25 each or 6 for $6.0
D                        |$0.15 each or 4 for $7.0
E                        |$2.0 each AND if buy one B get one E
Please enter 'continue' to continue with current pricing or 'set' to add new pricing
Please enter 'exit' to exit this program
>>>

If we want to update the volunm size and volunm price, volunm size and volunm price are optional

>>> >>>A 9.9 10 86.6
Product Code | Price
A                        |$9.9 each or 10 for $86.6
B                        |$10.0 each
C                        |$1.25 each or 6 for $6.0
D                        |$0.15 each or 4 for $7.0
E                        |$2.0 each AND if buy one B get one E

use regex to check if the input is vaild

>>>FF 9.9 9.9 9.9
NO MATCH!! Invalid input
>>>F 9.9 99 99.9
NO MATCH!! Invalid input

5. EXIT

exit -> terminate this process

>>>exit //then the execution will be terminated

test case

Scan these items in this order: ABCDABAA; Verify the total price is $31.24.

>>>ABCDABAA
Enter the products code you want to buy in a single line then Enter 'r' to get the total price(no space)
>>>r
The total price is $31.24

Scan these items in this order: CCCCCC; Verify the total price is $6.6.

Enter the products code you want to buy in a single line then Enter 'r' to get the total price(no space)
>>>CCCCCC
Enter the products code you want to buy in a single line then Enter 'r' to get the total price(no space)
>>>r
The total price is $6.6

Scan these items in this order: ABCD; Verify the total price is $14.74. Because get 1 B will get 1 E free, so the total price for ABCDE is also $14.74.

>>>ABCD
Enter the products code you want to buy in a single line then Enter 'r' to get the total price(no space)
>>>r
The total price is $14.74


Enter the products code you want to buy in a single line then Enter 'r' to get the total price(no space)
>>>ABCDE
Enter the products code you want to buy in a single line then Enter 'r' to get the total price(no space)
>>>r
The total price is $14.74

Scan these items in this order: ACDE; Verify the total price is $5.94.

Enter the products code you want to buy in a single line then Enter 'r' to get the total price(no space)
>>>ACDE
Enter the products code you want to buy in a single line then Enter 'r' to get the total price(no space)
>>>r
The total price is $5.94