1. Week 4 Recap CSE 115 Fall 2006 Section C

2. Decoupling Separation of concerns Defining what an object can do, not how it does it

3. Interfaces One way to achieve decoupling in Java is through interfaces. An interface definition consists of an interface header and an interface body.

4. Interface Header public interface Name  public: keyword – meaning the same as before  interface: keyword – indicating the start of an interface definition  Name: identifier – name of interface. Interface names by convention start off with a capital I, but then use same conventions as class names

5. Interface Body Enclosed in { } Contains what capabilities elements should have if they implement the interface.

6. Methods Formal specifications of capabilities inside our classes Method definitions consist of a method header and a method body

7. Method Definition (Method Header – Part 1) public type name()  public: keyword – as before  type: indication of the return type of the method – what information comes back from a method call? If no information comes back return type is void (another keyword)

8. Method Definition (Method Header – Part 2) public type name()  name: identifier for method – method names follow conventions of class names, except the names begin with a lower case letter.  (): called a formal parameter list – gives us a list of information that the method needs to finish its task.

9. Formal Parameter Lists Comma-separated list of formal parameters Formal parameters are listed giving the type of the parameter followed by a name (type1 name1, type2 name2, type3 name3…)

10. Calling methods To get the actions of a method to be performed, we need to call (or invoke) the methods Methods are called on objects  How do we get an object?

11. Method calls object.methodToBeCalled() Recall the dot (.) operator [or member access operator] Notice the () here – this is an actual parameter list. If the method needs a parameter, we need to give an actual value to the method when we call it.

12. Important Note Two methods in Java can not have the exact same method header.