CatchProcessor detects empty catch blocks.
ReferenceProcessor detects circular references between packages.
Factory example detects wrong uses of the factory pattern.
NotNullProcessor adds a not-null check for all method parameters.
MutationProcessor randomly mutates some parts of the abstract syntax tree for mutation testing.
The Nton example introduces a Nton design pattern (extension of singleton but for N instances) into a target class. It inserts static fields, methods, and initializer code into constructors.
The Database access example shows how to use annotation processing to add persistence into a POJO.
The Visitor example implements a visitor pattern by automatically introducing an accept method in a visited type hierarchy.
The Field Access example implements a refactoring that introduces setters and getters for the fields annotated with the Access annotation and that replaces all the direct accesses to these fields by calls to its new getters and setters.
The Distributed Calculus example creates a fun new language for distributed computing using Java and Spoon.