Access Control and Misc Terms

• Fields and methods can have any of the following access level. Classes can only have public and default access.

  Modifier	Same Class	Same Package	Subclass	Universe
  public	Yes	Yes	Yes	Yes
  protected	Yes	Yes	Yes
  default (no specified access mode)	Yes	Yes
  private	Yes

• The term binding refers to when the use of a variable, class, or method is resolved.
• Dynamic binding means that the reference is resolved at runtime.
• Static binding means that the reference is resolved at compile-time.
• Keep an eye out for examples of dynamic binding in Java.
• The term virtual method call refers to the way that polymorphism works in java - when a method is called, it is "virtual" because it is dynamically bound at runtime based on the class of the object being used.
• Static binding is more efficient because the compiler binds the call at compile-time.

• The keyword final indicates that the identifier is in some sense constant.
• You cannot subclass a final class
• You cannot override a final method
• Methods declared as final are sometimes used for optimization, since virtual method invocation will not be used.
• Methods marked as static or private are automatically final because dynamic binding cannot be applied in either case.
• A final variable is a constant
• If you mark a reference as final, that reference cannot refer to any other object. (But you can still change the contents of the object)
• You can set a final variable only once, but that assignment can occur independently of the declaration; this is called "blank final variable"
• The last opportunity to set a blank final instance field is in the constructor
• A blank final local variable (i.e. declared in a method) must be set in the method body before being used

• A class can contain code in a static block that does not exist within a method body
• Static block code executes only once, when the class is loaded
• A static block is usually used to initialize static (class) attributes
• Different static blocks within a class are executed in the order of their appearance in the class.

Constructor Invocation

Memory is allocated and initialized when a constructor is called. Instance variable initialization uses these steps recursively:

1. Bind constructor parameters.
2. If explicit this(), call recursively, and then skip to step 5.
3. Call recursively the implicit or explicit super call, except for Object.
4. Execute the explicit instance variable initializers.
5. Execute the body of the current constructor.