Refactoring. Replaced Integer with primitive type int

[ullenius]

Replaced Integer with primitive type int.

• No need for primitive type wrapper as Java does autoboxing (when using the value as a key for the HashMap)

• In this method the value can never be null since the method parameter defines an int (primitive type). Thus Integer is not needed

• Since Integer is immutable final int was used to clarify that this value will never be changed.

• The Integer(int value) constructor is deprecated as of Java 9. The Javadocs(https://docs.oracle.com/javase/9/docs/api/java/lang/Integer.html#Integer-int-) state:

"It is rarely appropriate to use this constructor. The static factory valueOf(int) is generally a better choice, as it is likely to yield significantly better space and time performance."

[coveralls]

Coverage remained the same at 68.578% when pulling 44a526222ce80a320196e6c48f1fc9489a2fd4e9 on ullenius:autoboxing into 7dbd34778e5b9ae498bb4efecb8d25d5e26ceb55 on mpatric:master.

[tmzkt]

I agree with your changes. Thank you for detailing all the reasons behind your change and for your contribution!