add slides for lecture 11

this is about code quality and more specific tools such are Checkstyle
and Spotbugs

lectures/revealjs/11-code-quality.adoc

+= Code quality 
+:customcss: slides.css
+:icons: font
+:includedir: revealjs/includes/
+:LECTURE_TOPIC: Code quality 
+:LECTURE_NO: 11th Lecture
+
+include::{includedir}header.adoc[]
+
+[.smaller-80][.center-paragraph]
+IT1901 Fall 2020 - {LECTURE_NO}
+
+
+[background-color = "#124990"]
+[color = "#fff6d5"]
+== Code quality
+
+== Code quality
+
+- automated tests
+- coding standards and consistent formatting
+- check for higher level types of errors (bug patterns)
+
+
+== Tools for automatic code checking
+
+- Checkstyle (https://checkstyle.sourceforge.io/index.html) 
+- Spotbugs (https://spotbugs.readthedocs.io/en/latest/index.html)
+- Pmd (https://pmd.github.io)
+- Sonarcube (https://www.sonarqube.org/)
+- ... 
+
+== Checkstyle
+
+- static analysis
+- finds errors like
+** references to variables with undefined value
+** variables that are never used
+** syntax and coding standards violations
+** dead code blocks 
+
+== Checkstyle (2)
+
+- naming conventions
+- line length
+- whitespace
+- Javadoc comments
+- annotations
+ 
+== Checkstyle (3)
+
+- can be configured to use a certain set of checks
+- extendable - one can write own checks
+- plugins for IDEs
+ 
+[background-color = "#124990"]
+[color = "#fff6d5"]
+== Checkstyle examples 
+
+ 
+== Spotbugs
+
+- checks bytecode and not the source
+- looks for "bug patterns"
+- example:
+
+```
+An apparent infinite loop (IL_INFINITE_LOOP)
+This loop doesn't seem to have a way to terminate (other than by perhaps throwing an exception).
+```
+
+== Spotbugs (2)
+
+- extendable
+- plugins for Maven Gradle Ant
+- Eclipse IDE integration 
+
+[background-color = "#124990"]
+[color = "#fff6d5"]
+== Spotbugs examples
+
+
+
+include::{includedir}footer.adoc[]
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