Constructors

• Along with constants, instance variables, and methods, the definition of a class may include constructors.
• Classes that are just used for their static methods and constants, like Utils in the Smarts program. do not need constructors, Other classes do. Constructors look like this:
  class-name (< parameters >) {
  < statements >
  }
• A class can have more than one constructor. Different constructors are distinguished by the number and/or the types of their parameters.
• To create a new instance of a class, you call the constructor preceded by the identifier new. For example, to create a new Brain, you would do something like new Brain(ui, sensor, effector, index), where ui, sensor, effector, and index are variables bound to UI, Sensor, Effector objects and some int respectively.
• When a constructor in a class is called (using new), it returns an object that is an instance of the class, but, unlike a method, the constructor does not have an explicit return statement.

© 2004. Indiana University and Michael Gasser. www.indiana.edu/~gasser/Q530/Notes/constructors.html 22 Sep 2004