Java Keywords

Some Java keywords for visibility:

• public
  • class - Class with main must be public and there can be only one public class per file.
  • method - Whether the method can be called from the world.
  • field - Is the field available from outside the package
• private
  • class - only accessible from within the package
  • method - only accessible from within the class
  • field - only accessible from within the class
• protected
  • class - ?
  • method - visible to package and all subclasses
  • field - visible to package and all subclasses
• default
  • all - visible to the package

Some other Java keywords:

• static
  • method - Whether you need an instance to call it (e.g. Math.pow())
  • field - see method.
• final
  • class - cannot be extended
  • method - cannot be overriden
  • field - value can be changed once (at construction), after that it cannot be changed. Beware of value vs reference issue!
• abstract
  • class - cannot be instantiated. Only useful for inheritance or variable types. Note: Not all methods are abstract.
  • method - method is not implemented, but must be implemented in children classes.
• transient - means not serializable, used with fields