[Example implementation](https://github.com/exercism/java/blob/master/exercises/matrix/.meta/src/reference/java/Matrix.java)

- Class: define a class to resolve the problem

- Constructors: initializing values when object is created

- Methods: define methods to expose functionalities

- Argument: constructor and methods takes values as arguments

- Strings: input of problem is a `String`

- Integer: work with integer values

- Assignment: assign some objects to local variables

- Variables: define references to structures

- Static Variables: define static references

- Loops: iterate on input and structures

- Return values: methods should return requested values

- Regular Expression: use expressions to split the input

- Arrays: use multidimensional arrays to manipulate the input