Scope

• Scope rules determine where in your code an identifier can be referenced.
  

• In Java, scope is determined by blocks of code (code within curly braces) and the class hierarchy of the current instance (more on hierarchies later, if time allows).
  

• When Java needs to resolve an issue of scope, it looks for an identifier's definition in the following order (and stops looking when the identifier is found):
  
  
  1. the current block
     
     
  2. surrounding blocks
     
     
  3. the class of the current instance (or current object)
     
     
  4. the superclasses of the current instance's class hierarchy
  
  
• This means that a local object with the same name as an instance variable will be found and used, not the instance variable.
  
  
• It is a good idea to avoid using the names in a class or its superclass(es) for local variables.
  
  
• If you do have local variables with the same identifier names and want to access the instance variables, use this.

• An identifier can only be referenced within the same block in which it has been declared, or if it has been declared in a surrounding block.
  
  
• Remember a block starts with an open curly brace and ends with a close curly brace.
  
  
• Since the outer-most curly braces is the class, this is the last block searched.
  
  
• An object that is declared within a method's block of code surrounded by curly braces is called a local object.
  

• An object declared in a method's signature is called a local parameter.