Is there a methodology or any objective standard to determine whether the code of the project is well-written? How to measure in a structural and scientific manner to access the quality of the code?

Many people say code review is important and always do encapsulation and data abstraction to ensure the quality. How can we determine the quality?

Can a structural, organised software design diagrams drawn implies good quality of code ?

If we type the code with good cautions of encapsulation and data abstraction, why review anyway?