Refactoring Java project with one Junit test file

Job ID: 32193663

Budget: $10 – $30 USD

Refactor Java Classes to improve code.
Clients need to be able to build Vehicle with combination of parts.
Clients need to able to choose default or their combination of parts.
Current Project Code is available.
It works with few combination of parts only.

Explain the Design Pattern that will best suit it.
Explain how code is refactored and how the new code improves it.