1. CS Week 4
Jim Williams, PhD

2. Understand vs. Apply Steph Curry, NBA Golden State Warriors
Basketball Analogy
Demonstration vs. Practice
Declarative Knowledge vs Procedural Knowledge
Importance of Practice for learning
If you watch the same video or even 10 different videos on how to shoot a basketball do you get better at shooting a basketball?
Steph Curry, NBA Golden State Warriors

3. This Week Team Lab: Using Objects Program(s) 3 (due Thurs):
Exam 1 conflicts: Scheduling rooms and alternatives we can offer. Expect alternative offering late next week.
Consulting hours: Request Help Queue
Lecture: Using Objects, Branches

4. What are values of variables?
name: Minsub\n
age: 22\nCS
major:
name: Minsub\n22\CS
age:
name: Minsub
age: 22
String note = "Minsub\n22\nCS";
Scanner input = new Scanner( note);
String name = input.nextLine();
int age = input.nextInt();
String major = input.nextLine();

5. Eclipse IDE Opening project, copying in files
Style and Commenting Guides
Strings
I/O
Calling methods
Compiler & Runtime Errors
Scanner reading a number

6. What are values of variables?
name: Minsub\n22\CS
age:
major:
name: Minsub
age: 22
name: Minsub
major: CS
String note = "Minsub\n22\nCS";
Scanner input = new Scanner( note);
String name = input.nextLine();
int age = input.nextInt();
String major = input.nextLine();

7. What are values of variables?
score1: 20
score2: 25
title: scores
title:
score1:
score2: scores
String note = "20 25\nscores";
Scanner input = new Scanner( note);
int score1 = input.nextInt();
int score2 = input.nextInt();
String title = input.nextLine();

8. java.util.Random Random randGen; //Declare reference variable
randGen = new Random(); //create instance
// randGen.setSeed( 123); //set state
int valueA = randGen.nextInt( 5); //get a value
int valueB = randGen.nextInt( 5);
int valueC = randGen.nextInt( 5);

9. Relational and Equality Operators
< <= > >= == !=
int n = 6;
boolean result = n != 5;
result: true
result: false

10. Logical Operators && (AND) both sides true to be true, else false
|| (OR) either side true then true, else false
! (NOT) if true then false, and vice-versa
!(a && b) == !a || !b //is this true or false?

11. Does !(a && b) == !a || !b Truth Table: a b a && b !(a && b) !a !b

12. What is result? boolean result = flag = false || flag; flag
true
false
try it.

13. == vs String equals() String str1 = "hello"; String str2 = "hello";
String str3 = new String("hello");
System.out.println( str1 == "hello" );
System.out.println( str1 == str2);
System.out.println( str1.equals("hello"));
System.out.println( str3 == str1);
System.out.println( str3.equals( str2));

14. Are these equivalent? boolean tired = true; if ( tired) {
Same result in all cases
Different result sometimes
Error
boolean tired = true;
if ( tired) {
//take break
tired = false; }
if ( !tired) {
//keep working
boolean tired = true;
if ( tired) {
//take break
tired = false;
} else {
//keep working }

15. Floating Down a River

16. Side Trip, maybe multiple side trips
boolean tired = true;
if ( tired) {
System.out.println(“take break”); }

17. One side of the Island or the other
boolean sunny = false;
if ( sunny) {
System.out.print(“sunny”);
} else {
System.out.print(“not sunny”); }
System.out.println( “ and back together”);

18. Equivalent? Yes No char chr = //any valid char out = 'W';
if ( chr == 'A') {
out = 'X';
} else if ( chr == 'B') {
out = 'Y';
} else {
out = 'Z'; }
char chr = //any valid
char out = 'W';
if ( chr == 'A') {
out = 'X';
} if ( chr == 'B') {
out = 'Y';
} if ( chr != 'A' || chr != 'B') {
out = 'Z'; }
Yes No

19. What is the value of msg? boolean flag = true;
String msg = "before if";
if ( flag = false); {
msg = "" + flag; }
before if
true
false

20. What is print out? a char choice = 'a'; switch (choice) {
case 'a': System.out.print("a");
case 'b': System.out.print("b");
break;
default: System.out.print("other"); } a b ab
other

21. Scanner Scanner input = new Scanner("1 \ntwo \n 2\n\n");
int a = input.nextInt();
if ( input.hasNextInt()) {
int b = input.nextInt();
} else {
input.nextLine(); }
String line = input.nextLine();
System.out.println("#" + line + "#");

22. Scanner num: 0 str4: 3 str4: line note. num: 3 str4:
String note = "Hmm\na \na\n3\n\nline note.";
Scanner input = new Scanner( note);
int num = 0;
String str1 = input.nextLine();
String str2 = input.next();
if ( input.hasNextInt()) {
num = input.nextInt(); }
String str4 = input.nextLine();

23. Debugging with Print statements
See what is going on.
Divide and conquer.