Cyclomatic complexity is the count of linearly independent paths in a program's source code. With the help of control flow graph, we can use the following formula to calculate this:

CC = E - N + 2P

Related
Control Flow Graph

A notation of all the paths that can be traversed by an executing program.

Common Constructs

Composition

Using some functionalities of a class but doesn't inherit (i.e. is-a relationship) it, is known as composition (i.e. has-a relationship).

Reasons to Favor Composition Over Inheritance

• Composition offers a better testability. Imagine a class composed of another class or interface. You can easily create a mock of the composed class for the sake of testing.
• Composition is more flexible than inheritance. It is easier to change the implemention of the composed class with better and improved version. Just create a new independent implementation (e.g. annonymously) of the composed class and change it at runtime.
• Both composition and inheritace supports code reuse. However, inheritance breaks encapsulation. Example, if a subclass is depending on its super class behavior for its operation, it becomes fragile. Try to imagine that you change the implementation on the super class. Did you consider the effect of the change on the subclasses that overrides it but partially depends on it. In composition there's no dependencies like this. Thus, you have more robust code.

A method that accepts the same set of inputs will always produce the same output.

Java Example

java.lang.Boolean.valueOf("TRUE")