1. 1. Cyclomatic complexity
Introduced by Thomas McCabe in 1976, it measures the number of linearly-independent paths through a program.
Cyclomatic complexity is a measure of source code complexity.
When computing the Cyclomatic Complexity, the result is returned as a number.
The bigger the number, the more complex the program is.

2. Complexity  V(G) = edges – nodes + 2
The metric tries to capture the number of paths through the code.
The complexity typically increases because of branch points.
To compute the Cyclomatic complexity:
Complexity  V(G) = edges – nodes + 2
Example:

3. Complexity  V(G) = edges – nodes + 2
If(success)
Do something;
Else
Do the other thing;
V(G) = 4 –4+2 = 2

4. 2. Comments percentage %
The goal is to maximize code understandability.
The more you provide documentation, the more people understand it.
Comments% = comment lines / total number of lines.

5. 3. Size (Number of Lines)
The size can be found by counting the non-empty lines.
Comment Lines, and Java_doc Lines are counted too.
4. Weighted Methods
The methods in a class are counted.
The more there are methods, the class becomes more complex

6. For each method, the number of lines is counted.