Week 4 Recap

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.