CP122 CS I. Chapter 5: Decisions

Transcription

1 CP122 CS I Chapter 5: Decisions

2 Amazon Go: Just walk out shopping Tech News!

3 Tech News! Amazon Go: Just walk out shopping EU finds that Google, Twitter, and Facebook often fail to censor hate speech

4 Hackers' Tip of the Day: Detecting Artificial Intelligence How do we know if a program is actually artificially intelligent?

5 Hackers' Tip of the Day: Detecting Artificial Intelligence A chatbot is program that tries to have a conversation with you. JabberWacky

6 Hackers' Tip of the Day: The Turing Test Alan Turing devised a test of AI. Can a computer fool a human into thinking it's also human?

7 Hackers' Tip of the Day: The Turing Test The Imitation Game.

8 Program Structure Review header comment imports class definition instance variables methods main method

9 Program Structure Review header comment imports class definition instance variables methods other class definition main method

10 Chapter 5: Making Decisions How can the computer make decisions? How are different values compared? What are Boolean expressions and variables?

11 Program Control Flow public class MyProgram { public static void main(string[] args) { // Statement 1 // Statement 2 // Statement 3 // Statement 4

12 Program Control Flow public class MyProgram { public static void main(string[] args) { // Statement 1 // Statement 2 // Statement 3 // Statement 4

13 How can we make our programs do different things?

14 Make Decisions public static void main(string[] args) { String iqstring = JOptionPane.showInputDialog( What is your IQ? ); int iq = Integer.parseInt(iqString); if (iq > 150) { System.out.println( You're a genius! );

15 Make Decisions A boolean condition: public static void main(string[] args) { String iqstring = JOptionPane.showInputDialog( evaluates to true or What is your IQ? ); false int iq = Integer.parseInt(iqString); if (iq > 150) { System.out.println( You're a genius! );

16 Make Decisions The body of the if- public static void main(string[] args) { String iqstring = JOptionPane.showInputDialog( statement is only executed What is if your the IQ? ); int iq = Integer.parseInt(iqString); condition is true. if (iq > 150) { System.out.println( You're a genius! );

17 Make Decisions public static void main(string[] args) { String iqstring = JOptionPane.showInputDialog( What is your IQ? ); int iq = Integer.parseInt(iqString); if (iq > 150) { System.out.println( You're a genius! ); else { System.out.println( Sorry! You're not a genius );

18 Make Decisions public static void main(string[] args) { String iqstring = JOptionPane.showInputDialog( What is your IQ? ); int iq = Integer.parseInt(iqString); The body of the elseclause is only executed if (iq > 150) { if the condition is false. System.out.println( You're a genius! ); else { System.out.println( Sorry! You're not a genius );

19 Make Decisions public static void main(string[] args) { String iqstring = JOptionPane.showInputDialog( Notice: else is not followed by a What condition. is your IQ? ); int iq = Integer.parseInt(iqString); It always executes if the if condition is false. if (iq > 150) { System.out.println( You're a genius! ); else { System.out.println( Sorry! You're not a genius );

20 Make Multiple Decisions if (iq > 150) { System.out.println( You're a genius! ); else if (iq > 125) { System.out.println( You're pretty smart. ); else if (iq > 100) { System.out.println( You're kinda smart. ); else { System.out.println( I've got some bad news... );

21 Make Multiple Decisions if (iq > 150) { System.out.println( You're a genius! ); else if (iq > 125) { System.out.println( You're pretty smart. ); else if (iq > 100) { System.out.println( You're kinda smart. ); else { System.out.println( I've got some bad news... ); Each else-if condition is only checked if the above conditions are all false.

22 Make Multiple Decisions if (iq > 150) { System.out.println( You're a genius! ); else if (iq > 125) { System.out.println( You're The else pretty block smart. ); is only executed if all the above else if (iq > 100) { conditions are false. System.out.println( You're kinda smart. ); else { System.out.println( I've got some bad news... );

23 Comparison Operators == : equal to < : less than > : greater than <= : less then or equal to >= : greater than or equal to!= : not equal to

24 Sequential ifs x = 5; y = 17; if (x < 10) { System.out.println( Small x ); if (y > 25) { System.out.println( Big y );

25 Sequential ifs x = 5; y = 17; if (x < 10) { System.out.println( Small x ); if (y > 25) { System.out.println( Big y ); else { System.out.println( Small y );

26 String/Object Comparison Operator String name1 = Terry ; String name2 = Tracy ; // DOESN'T WORK LIKE YOU THINK! if (name1 == name2) { System.out.println( A MATCH! );

27 String/Object Comparison Operator String name1 = Terry ; String name2 = Tracy ; // DOESN'T WORK LIKE YOU THINK! if (name1 == name2) { System.out.println( A MATCH! ); // WORKS! if (name1.equals(name2)) { System.out.println( A MATCH! );

28 Nested if-statements if (numberhomeruns > 30) { if (numberstrikeouts < 100) { System.out.println( You're a great hitter! ); else { System.out.println( You have power, ); System.out.println( but you miss too often );

29 boolean Variables boolean mybool = (x < y); if (mybool) { System.out.println( x is smaller than y );

30 Compound Boolean Conditions if (iq < 150 && iq > 125) { System.out.println( You're pretty smart. );

31 Compound Boolean Conditions if (iq < 150 && iq > 125) { System.out.println( You're pretty smart. ); Boolean AND

32 Compound Boolean Conditions if (iq > 150 iq < 50) { System.out.println( You're at one of the extremes ); Boolean OR

33 Truth Tables for AND and OR

34 Compound Boolean Conditions if (125 < iq < 150) { System.out.println( You're pretty smart. ); This doesn't work!

35 Worksheet

36 Comparing Objects // Return true if both Vectors are the same // Return false if they are at all different public boolean equals(vector other) { if (x == other.getx() && y == other.gety() && z == other.getz()) { return true; else { return false;

37 Comparing Zombies

38 Photoshopper