1. Introduction to Programming
Ms. Knudtzon
C Period
Monday Sep 27
Week 4

2. Introduction to Commenting Code
Comments before signature of methods
To tell what the method does
Comments for variables
To explain what the variable holds, what they are used for
Comments within methods
To explain what is going on; used when it is not immediately clear from looking at the code
Also, this allows me to see what you are trying to do, even if your code doesn’t work!
Make the comments be pseudocode if you can’t get your code to work!
Look at Circle Class with only has comments before signature of methods – but all the stuff Circle code does is straight-forward
Look at Java Eyes – sometime there is no comment before a method (Bad Programming Practice)  look at the setPhysics method – we have no way when just looking at that method to know what the int we pass in is used for or what values work for the parameter
But in that code there are comments that explain exactly what variables hold and what they are used for and there are several examples where the comments explain what a block of code does  these kind of comments help people who are reading this code figure out what it does, and it helps you when you go to change the code to understand where to begin
Week 4

3. Objects as Data Types
Object data types are not the same as primitive data types
They are references to the object, instead of containers holding the object
A reference is like a pointer or an address of an object
A good way to think of this object reference is as a remote control
BlueJ gives you a good way of looking at the references too…
Week 4

4. The Dot Operator
A Dog remote control would have buttons to do something (to invoke the dog’s methods)
Dog myDog = new Dog();
myDog.bark();
DOG
Eat
Bark
Wag
Built-in data type containers hold the actual value (Java has made the storage for them)
But object data types (like Strings and objects we create) tell a way to get to the object so that you can tell the object what you want it to do.
Dog myDog  Declare a reference variable
new Dog()  creates the object (make space for this object to exist – “on the heap”
Dog myDog = new Dog()  link the object and the reference together (Program the remote control)
Think of the dot operator like pushing a
button on a remote control
Imagine this is a
Remote control
Week 4

5. Objects starting other objects
Objects can create other objects
Why would they want to do this?
How do they do this?
DMV dmv = new DMV();
dmv.getLicensePlate();
Talk about why in class
Week 4

6. Grades Homework Handout: Let’s look at this
How would we model the classes we need to make?
How do we start?
Week 4

7. Introduction to Programming: Review for Test
Ms. Knudtzon
C Period
Tuesday Sep 28
Week 4

8. Introduction to Programming: Test 1
Ms. Knudtzon
C Period
Wednesday Sep 29
Week 4

9. Introduction to Programming
Ms. Knudtzon
C Period
Thursday Sep 30
Week 4

10. Conditional Statement
Used for checking if a certain condition has been met
int amount; //this is set somewhere else
if (amount > 0){ /*in () is a statement that
gives a true or false result */
//do something }
else{
//do something else
Week 4

11. What if there are several conditions you want to check?
int amount; //this is set somewhere else
if (amount == 0){ //notice the ==
//do something }
else if (amount < 0) {
//do something else
else { // amount must be > 0…
//do something different
Week 4

12. What if two things have to be true?
if (amount > 0 && open > 0){
//do something }
&& means “and” – it joins together the two boolean conditional statements and IF both are true, then the entire statement is true, if only one is true, then the statement is false
Week 4

13. What if one of two things could be true but both don’t have to be?
if (amount > 0 || open > 0){
//do something }
|| means “or”
Week 4

14. What if you already have a boolean value?
boolean flag;
if (flag){
//if flag is true this happens }
else {
//flag is false so this happens
Week 4

15. Tricking you…
The brackets in the “if” and “else” statements are optional in Java
BUT only if you want to execute ONE statement after the if or else statement
if (amount == 0)
System.out.println(“okay”);
else
System.out.println(“nonzero amount”);
if(amount == 0)
amount = 500;
System.out.println(“amount equal to 0”);
amount = 200;
System.out.println(“amount was not equal to 0”);
AP tests tries to trick you with questions like this!!
Week 4

16. More Nesting if (grade > = 90){ System.out.println(“A”); }
else if (grade > = 80) {
System.out.println(“B”);
else if (grade > = 70){ System.out.println(“C”);
else if (grade > = 60){ System.out.println(“D”);
else {
System.out.println(“F”);
Week 4

17. while Loop while (amount > 0){ /* do something
and only stop doing it if
the amount becomes 0 or less */ }
Week 4

18. Reading
D&D : Chapter 4: Conditional Statements: Part 1 (Can read or skim – covers if/else and while)
Note: The reading introduces the code without brackets first… (I think it’s a bad programming practice, especially for beginners  see Good Programming Practice 4.4)
Also note: D&D puts everything in a main method – there are good reasons why we have not learned to program this way
D&D : Chapter 5: Conditional Statements: Part 2 (Sections – covers for loops)
Week 4

19. Introduction to Programming
Ms. Knudtzon
C Period
Friday Oct 1
Week 4

20. Funny PseudoCode Dave writes: Georg writes:
if(you're around at the right time && georg does not do it
instead) {i'm there}
else {i sit in my cubicle and cry.}
Georg writes:
while(I don't like showing off && !kids_saw_the_printer) {
Dave shows off the printer;
kids_saw_the_printer = true; }
we go to the pixar talk;
we go to cake love;
return to home;
Week 4

21. Getting Input From A User
I’ve made a class for you to use to get input from the terminal window
InputReader
What is input?
How is different from calling a method and typing in a parameter?
Week 4

22. Input
Input is something a non programmer might input to your computer program.
It could be anything
Text:
Inputting a password
Filling out forms
Doing math equations
Asking the computer questions
Telling the computer your feelings
But Also: Mouse/ Joystick Input
Clicking buttons to do something
Commands to a video game
etc
Week 4

23. Can Machines Think?
Turing (1950) describes the following kind of game. Suppose that we have a person, a machine, and an interrogator. The interrogator is in a room separated from the other person and the machine. The object of the game is for the interrogator to determine which of the other two is the person, and which is the machine. The interrogator knows the other person and the machine by the labels ‘X’ and ‘Y’ -- but, at least at the beginning of the game, does not know which of the other person and the machine is ‘X’ -- and at the end of the game says either ‘X is the person and Y is the machine’ or ‘X is the machine and Y is the person’. The interrogator is allowed to put questions to the person and the machine of the following kind: “Will X please tell me whether X plays chess?” Whichever of the machine and the other person is X must answer questions that are addressed to X. The object of the machine is to try to cause the interrogator to mistakenly conclude that the machine is the other person; the object of the other person is to try to help the interrogator to correctly identify the machine.
Week 4

24. Turing Test http://en.wikipedia.org/wiki/Turing_test
Eliza – The Computer Therapist (better than my simple one)
Loebner Prize
Contest each year, up to a $100,000 award
Loebner Prize
$2,000 for the most human seeming of all bots for that year - awarded every year
$25,000 for the first bot that judges cannot distinguish from a real human in a text-only based Turing Test (awarded once only)
$100,000 to the first bot that judges cannot distinguish from a real human in a Turing Test that includes deciphering and understanding text, visual, auditory (and tactile?) input.
The Loebner Prize dissolves once the $100,000 prize is won.
Week 4

25. What else can input do? Two Simple Demos: Math program
Bad Turing test contender
Week 4

26. Pop-up windows Like the javax.swing.JOptionPane
String input = JOptionPane.showInputDialog(“Enter first number”);
int num = Integer.parseInt(input);
//Display Final Results
String result = "program got input: " + num;
JOptionPane.showMessageDialog(null, result, “Program Results”, JOptionPane.INFORMATION_MESSAGE);
But this program does not check to make sure the user actually inputs an integer  can get a run-time error! (The InputReader program forces the user to keep entering input until they input the expected type)
From Java Docs, look up JOption Pane to see what it does
showMessageDialog(Component parentComponent, Object message, String title, int messageType)
parentComponent - determines the Frame in which the dialog is displayed; if null, or if the parentComponent has no Frame, a default Frame is used
message - the Object to display
title - the title string for the dialog
messageType - the type of message to be displayed: ERROR_MESSAGE, INFORMATION_MESSAGE, WARNING_MESSAGE, QUESTION_MESSAGE, or PLAIN_MESSAGE
Week 4

27. Beyond while loops…
What happens if you want to do the same thing a number of times (5 times, 10 times, etc)
Also what if you want to do some sort of calculation a certain number of times
Use a “FOR” loop
for(int x = 0; x < 5; x++){
System.out.println(“hello”); }
Week 4

28. What’s ++ Other math shortcuts
++ is a shortcut (unary increment operator)
x++  x = x+1
Other math shortcuts
x-- (unary decrement operator)
x+=5
x-=10
x*=3
Note: x++ is different than ++x (Pre versus post operators)
++x -- Preincrement – increment x by 1 first then use the new value of x in anything that follows
X++ - post increment – use current value of x in anything that follows and then increment it by 1
Week 4

29. Let’s examine this for(int x = 0; x < 5; x++){
//the body of the loop }
Loop conditions:
1st: declare a starting value for the loop
2nd: define when the loop will stop (any conditional statement)
3rd: declare how the loop variable is incremented
Keyword “for” starts out the loop
() around the loop conditions
1st: declare a starting value for the loop
2nd: define when the loop will stop (any conditional statement)n  “Loop-continuation condition”
3rd: declare how the loop variable is incremented
In loop conditions – declare a looping variable, in this case I am declaring a variable called x (looping variables are also ints – because you have to do something a specific integer number of times), then I initialize that value to 0 (you could initialize it to whatever you want, then set the stopping condition – this stops when x < 5 (which means that when x==5, the statement inside the loop won’t be called because x is no longer less than 5.) The last statement in the loop condition increments the loop variable (which actually happens after the loop body is executed) Note: the loop variable can be incremented by any int value you want)
Week 4

30. Class Exercises
Write a for loop that prints the numbers 10 to 100 (in increments of 10)
for(int i = 10; i <=100; i= i+10){
System.out.println(i); }
Week 4

31. Weekend Homework Reading (Deitel & Deitel) Journal
Explore your progress thus far and your thoughts about the class. Are we moving too fast? Too slow? Do you think the material is explained clearly? What more could I do to help you learn better in this course?
Week 4