Static variables and methods

• Class variables are declared using the keyword static. A class variable belongs to an entire class; it can have only one value. A class variable is accessed from outside of the class with the class name followed by the dot operator. For example, in Brain there is a class variable for the exploitation rate used in making decisions. It is declared like this:

  public static double exploitationRate;
  

  And to access the value of the variable from another class, we do Brain.exploitationRate.
• A static method (class method), like a class variable, belongs to a whole class and is declared using the keyword static. A static method cannot make reference to any object instance variables or dynamic (non-static) methods in its body (since it can't possibly know which object is referred to), unless these are explicitly associated with particular objects. A static method is called from outside its class using the class name followed by the dot operator. For example, to call the static method random() from the built-in Math class, we do Math.random().

© 2004. Indiana University and Michael Gasser. www.indiana.edu/~gasser/Q530/Notes/static.html 11 Oct 2004