ImmutableCar

A demonstration of an immutable class with a variety of Java features, including the following:

Immutability:

• denoted by the usage of the 'final' keyword on both the class fields and the class itself
• promotes thread safety in multithreaded environments
• prevents unexpected side effects
• protects against null reference errors

Exceptions and argument checks:

• arguments supplied to the constructor are verified to be both non-null and valid
• failure to meet these criteria results in throwing the proper exception
• it is better to fail earlier than later

Enums and constants

• enum is preferred where a limited set of values are to be expected
• constants are utilized in testing for model names
• enums and constants prevent errors caused by using "magic" numbers and values

Encapsulation

• class fields are marked private and accessible only by the getter/accessor methods
• no setters/mutators are present because it is an immutable class

Overriding

• equals() and hashCode() have both been overridden, following the same ordering of fields utilized
• compareTo() has been overridden, as required by implementing the Comparable interface, following the same ordering of fields as equals() and hashCode()
• toString() has been overridden such that it returns a human-readable value

Testing

• JUnit unit tests
• full test coverage (class, method, and line coverage)