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# Fields/state

* A field is a data member of a class. Unless specified otherwise, a field can be public, static, not static and final

## static final

## final

## static variables

## Variable scope

## When to use fields

* If it will be used by the whole class not just a method
  * This depends if the class is a single method class (command pattern)
* It is the state of the instance
* There is only one instance of the object passed into the field which is fixed at compile time
  * If using dependency injection, this implementation can be different at runtime
* You should never use a field to simplify passing data from one method to another method.
* The object of the field will always be used in same way ie call to some instance method to apply some logic
  * Where as the parameter, depending on its state may be used differently

### When to use over a method variable or parameters

* Parameters constantly change, when the method is called.

## Links