Refactoring (Part 3)

• Decompose/Consolidate Conditional
  You have a complicated conditional (if-then-else) statement - Extract methods from the condition : if and else parts
• Consolidate Duplicate Conditional Fragments
  The same fragment of code is in all branches of a conditional expression - Move it outside of the expression.
• Remove Control Flag
  You have a variable that is acting as a control flag for a series of boolean expressions - Use a break or return instead.
• Replace Nested Conditional with Guard Clauses
  A method has conditional behavior that does not make clear the normal path of execution - Use guard clauses for all the special cases : The guard clause either returns, or throws an exception.
• Replace Conditional with Polymorphism
  You have a conditional that chooses different behavior depending on the type of an object - Move each leg of the conditional to an overriding method in a subclass. Make the original method abstract.
• Introduce Null Object
  You have repeated check for a null value - Replace the null value with a null object.
• Introduce Assertion
  Make the assumption explicit with an assertion.