1	Object Oriented Programming Chapter 2 introduces Object Oriented Programming. OOP is a relatively new approach to programming which supports the creation of new data types and operations to manipulate those types. This presentation introduces OOP.
2	What is this Object ? There is no real answer to the question, but we’ll call it a “thinking cap”. The plan is to describe a thinking cap by telling you what actions can be done to it.
3	Using the Object’s Slots You may put a piece of paper in each of the two slots (green and red), with a sentence written on each. You may push the green button and the thinking cap will speak the sentence from the green slot’s paper. And same for the red button.
4	Example
5	Example
6	Example
7	Thinking Cap Implementation We can implement the thinking cap using a data type called a class.
8	Thinking Cap Implementation The class will have two components called greenWords and redWords. These compnents are strings which hold the information that is placed in the two slots. Using a class permits two features . . .
9	Thinking Cap Implementation The two components will be private instance variables. This ensures that nobody can directly access this information. The only access is through methods that we provide for the class.
10	Thinking Cap Implementation In a class, the methods which manipulate the class are also listed.
11	Thinking Cap Implementation
12	Thinking Cap Implementation
13	Using the Thinking Cap A program that wants to use the thinking cap can import the ThinkingCap class.
14	Using the Thinking Cap Just for fun, the example program will declare two ThinkingCap variables named student and fan.
15	Using the Thinking Cap The variables are examples of reference variables, which means that they have the capability of refering to ThinkingCap objects that we create with the new operator.
16	Using the Thinking Cap Once the ThinkingCaps are created, we can activate methods such as slot for the student thinking cap.
17	Using the Thinking Cap Once the ThinkingCaps are created, we can activate methods such as slot for the student thinking cap.
18	Using the Thinking Cap The method activation consists of four parts, starting with the variable name.
19	Using the Thinking Cap The variable name is followed by a period.
20	Using the Thinking Cap After the period is the name of the method that you are activating.
21	Using the Thinking Cap Finally, the arguments for the method. In this example the first argument (newGreen) is "Hello" and the second argument (newRed) is "Bye".
22	A Quiz How would you activate student's pushGreen method ? What would be the output of student's pushGreen method at this point in the program ?
23	A Quiz Notice that the pushGreen method has no arguments. At this point, activating student.pushGreen will print the string Hello.
24	A Quiz Trace through this program, and tell me the complete output.
25	A Quiz Hello Go Cougars! Bye
26	What you know about Objects Class = Data + Methods. You know how to write a new class type, and place the new class in a package. You know how to import the class into a program that uses class type. You know how to activate methods. But you still need to learn how to write the implementations of a class’s methods.
27	Thinking Cap Implementation
28	Thinking Cap Implementation There is one feature about a method’s implementation . . .
29	Thinking Cap Implementation Within the body of the method, the class’s instance variables and other methods may all be accessed.
30	Thinking Cap Implementation Within the body of the method, the class’s instance variables and other methods may all be accessed.
31	Thinking Cap Implementation Within the body of the method, the class’s instance variables and other methods may all be accessed.
32	Thinking Cap Implementation Within the body of the method, the class’s instance variables and other methods may all be accessed.
33	Thinking Cap Implementation Here is the implementation of the pushGreen method, which prints the green Words:
34	Thinking Cap Implementation Here is the implementation of the pushGreen method, which prints the green Words:
35	A Common Pattern Often, one or more methods will place data in the instance variables...
36	Summary Classes have instance variables and methods. An object is a variable where the data type is a class. You should know how to declare a new class type, how to implement its methods, how to use the class type. Frequently, the methods of an class type place information in the instance variables, or use information that's already in the instance variables. In the future we will see more features of OOP.
37	THE END