1. CS Week 3
Jim Williams, PhD

2. Learning and Effort Influence Intelligence
"...effort and difficulty, that's when their neurons are making new connections, stronger connections. That's when they're getting smarter." - Carol Dweck

3. What are you doing (mentally)?
Images:

4. Exam Confirmation and Accommodation requests due by Friday
Week 3
Exam Confirmation and Accommodation requests due by Friday
P1 Milestone 1 due Thursday 8:00am

5. 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 }

6. Floating Down a River

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

8. 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”);

9. 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

10. Dangling Else - What is out?
int value = 0;
String out = "abc";
if ( value >= 1 ) if ( value <= 10) out = "1 to 10";
else out = "else";
out: abc
out: 1 to 10
out: else
out: abcelse

11. Values of a1 and a2? String str1 = "Hello";
a1: true
a2: true
a1: false
a2: false
String str1 = "Hello";
String str2 = new String( "Hello");
boolean a1 = str1 == str2;
boolean a2 = str1.equals(str2);

12. Values of a1 and a2? char ch1 = 'H'; String str = "Hello";
a1: true
a2: true
a1: false
a2: false
char ch1 = 'H';
String str = "Hello";
char ch2 = str.charAt(0);
boolean a1 = ch1 == ch2;
boolean a2 = ch1.equals(ch2);

13. 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);

14. Eclipse IDE (Integrated Development Environment)
Interpreter
Translator
Users
Editor
(Virtual)
Machine
Compiler
Hello.java
Hello.class
Computer
Files
Programmer

15. Programming Errors Syntax/Compile time Runtime & Logic Files
Editor
(Virtual)
Machine
Compiler
Hello.java
Hello.class
Computer
Files
Programmer

16. Programming Errors Syntax compiler error Logic
program runs but provides wrong values
Runtime
program crashes or throws exception

17. Debugging print statements Java Visualizer Breakpoints in Eclipse

18. 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

19. char - Which will compile?
1, 2, 3
1, 3 1
2, 3
int intValue = 0;
char aChar = 'B';
intValue = aChar; // 1
aChar = intValue + 1; // 2
aChar = '\u0041'; // 3

20. Increment && Decrement
i = i + 1;
i += 1;
i++;
++i;
i = i -1;
i -= 2;
--i;
i--;

21. Week 3
Exam Confirmation and Accommodation Requests Due Tomorrow

22. Puzzle int i = 5, j = 2, k; j += 3; k = i++ + --j;
After this executes, what are the values in i, j and k?

23. Puzzle int i = 5, j = 2, k; j = i + 3; k = i++ + --j - 1;
After this executes, what are the values in i, j and k?

24. Floating Down A Circular River?!

25. How many times will this execute?1
until num > 0
until num <= 0
Scanner input = new Scanner(
System.in);
int num;
int sum = 0;
do {
num = input.nextInt();
sum += num;
} while ( num > 0);

26. Body of While will execute...
boolean finished = false;
while ( !finished) {
String line = input.nextLine();
if ( line.equals("done")) {
finished = true;
} else {
System.out.println("echo:" + line); }
until "done" is input
never
forever
other?

27. How many "hello"? for ( int a = 0; a <= 5; a++) {
System.out.print("hello "); } 4 5 6
other?

28. How many "hello"? for ( int a = 5; a >= 1; a++) {
System.out.print("hello "); } 4 5 6
other?

29. How many "bye"? for ( int i = 1; i <= 5; i++) {
for ( int j = 2; j < 6; j++) {
System.out.print("bye "); } 5 9 20
other?

30. What does this print? for ( int i = 1; i <= 5; i++) {
1,1 1,2 1,3
2,1 2,2 2,3
3,1 3,2 3,3
4,1 4,2 4,3
5,1 5,2 5,3
1,1 2,1 3,1
1,2 2,2 3,2
1,3 2,3 3,3
1,4 2,4 3,4
1,5 2,5 3,5
for ( int i = 1; i <= 5; i++) {
for ( int j = 1; j <= 3; j++) {
System.out.print(i+","+j+" "); }
System.out.println();

31. What is the value of count?3 9 12
other
int count = 0;
for ( int i = 1; i < 4; i++) {
for ( int j = 6; j > 3; j--) {
count += 1; }
System.out.println("count=" + count);

32. What is the value of sum? 3 9 12 other int sum= 0;
boolean done = false;
for ( int i = 1; i < 4 && !done; i++) {
for ( int j = 6; j > 3; j--) {
if ( j > 4) continue;
sum += 1; }
if ( i == 3) break;
System.out.println("sum=" + sum); 3 9 12
other

33. Scanner num: 0 str4: line str4: line note. num: 3 str4:
String note = "Hmm\na 3\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();

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