Summary 7

• A subclass inherits the public variables and methods of the superclass, and has access to the public constructors of the superclass.

• Superclasses have no access to the methods of their subclasses; subclasses have no direct access to private variables of their superclasses.
• To write a subclass, we must include the keyword extends and the name of the class we are extending in the class definition.

  public class Subby extends TheSuper { }

• The keyword this is used to call methods - both inherited and native - of the current instance of a class.
• A method in the subclass which has the same name as a method of the superclass, overrides the superclass method.
• The keyword super is used to access a method of the superclass:

  super.aMethod()  //calls a superclass method

• The syntax super(arguments) is used to call a constructor of the superclass. This call must be the first line of code in a subclass constructor.
• Javadoc will correctly generate documentation for a superclass and its subclasses if all the required files are placed in the same folder in which javadoc is called.
• If more than one constructor is present in the same class, the constructor is overloaded. Overloaded constructors must carry different parameters, or a different number of parameters if the data type of the parameters is the same.
• Methods are overloaded in a class by giving them the same name, but a different number or type of parameter(s). Merely a different return data type is not sufficient to overload a method, and is not legal.
• The Math.random() method is used to generate random numbers.
• The System.out.print() method prints to the current line in the console.  

 © G. Hearn, & University of the Western Cape, 2006