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Nelson Series Talk

Security, Liberties and Trade-offs in the War on Terrorism. Nelson Series Talk.

kenyon-oneill
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Nelson Series Talk

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  1. Security, Liberties and Trade-offs in the War on Terrorism Nelson Series Talk Since 9/11, we have enacted the Patriot Act, tighter screening at airports, a proposed national I.D. card system, a color-coded national alert system, irradiated mail, and a Department of Homeland Security, but do all of these things really make us any less vulnerable to another terrorist attack? Security expert Bruce Schneier evaluates the systems that we have in place post-9/11, revealing which of them actually work and which ones are simply "security theater." Learn why most security measures don't work and never will, why bad security is worse than none at all, and why strong security means learning how to fail well. Most of all, learn how you can take charge of your own security - personal, family, corporate, and national. Wed, 11/10 7:00 pm http://www.counterpane.com/ http://www.schneier.com/ Bruce Schneier is an internationally renowned security expert. He is the author of eight books--including the best sellers "Beyond Fear: Thinking Sensibly about Security in an Uncertain World," "Secrets and Lies," and "Applied Cryptography"--as well as the Blowfish and Twofish encryption algorithms. His influential newsletter, Crypto-Gram, is read by over 100,000 people. Bruce Schneier

  2. Midterm #2 next Friday, 11/12 Week 10 in CS 5 Wolfgang Puck: not an object-oriented chef! Object-oriented programming We’re breaking out of the CS5App class Lab:A-L class CS5App { public static void main(String[] args) … due Sunday, 11/7 at midnight M/T sections • HW 10 (2 problems) due Monday, 11/8 at midnight W/Th sections Hw10 Pr1: Connect Four Hw10 Pr2: Virtual Art! PAIR Caution: This is very new stuff… Come to recitation (Fri @ 8) for help!

  3. Gaussian Elimination public static void solve(double[][] A) { for (int c=0 ; c<A[0].length-1 ; ++c) // columns { multRow( A, c, 1/A[c][c] ); // diag = 1.0 for (int r=0 ; r<A.length ; ++r) // rows { if (c != r) // off-diagonal elements become 0.0 { addMxRaToRb( A, -A[r][c], c, r ); } } } } dest row multiplier dest row source row multiplier

  4. Arrays: the good and bad + lots of computer work for little programmer work! you have to use the array’s naming convention A[r][c] - only one built-in capability: length Not everything is a bunch of identical boxes! int[] int int int A A[2] A[0] A[1] Classes and Objects take care of all 3 drawbacks...

  5. Classes & Objects An object-oriented programming language allows you to build your own customized types of variables. (1) A class is a type of variable. (2) An object is one such variable.

  6. But Why ? • Flexibility create-your-own • Reusability write once, take anywhere • Abstraction worry once, use anywhere ordinary data structures

  7. Java’s Library of Classes details on the data and methods that each class offers… ~ 3000 classes available java.sun.com/j2se/1.4.2/docs/api/index.html

  8. Objects An object is a data structure (like an array), except (1) Its data elements need not be the same type. (2) Its data elements have names chosen by the programmer. (3) Its data can be protected from unauthorized changes! (4) An object can have behaviors built-in by the programmer. int double hours npeople String Course c name String String[] String clist void addStudent(String s) int numStudents() Names!

  9. You’ve done all this before... String s = “I’m an object!”; String s2 = “I’m another object!”; if (s.equals(“I’m an object!”)) { s2 = “Ask me to do something!”; } int L = s2.length(); char c = s2.charAt(22); the dot indicates selection or containment the equals method is a built-in capability of String objects 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 nonstatic methods are called by an object static methods are called by a class, e.g. Math.sqrt(d); another nonstatic method

  10. Classes v Objects: some examples (1) A class is a type of variable. (2) An object is such a variable. the classes are in blue the objects are in green String s=“I’m an object!”; Strings are used so much new is not required… Course c=new Course(“cs5”); Course c2=new Course(“chem”); Board b=new Board(6,7); special constructor methods used with new Date d= new Date(11,13,2004); Date d2= new Date(11,25,2004);

  11. Coding classes and objects: in main int double hours npeople data String name Course c … String String[] String clist Course(String name) “constructor” void addStudent(String s) methods int numEnrolled() public static void main(String[] args) { Coursec = new Course(“cs5”); // constructc c.addStudent(“Michael”); //add a student H.pl(c.numEnrolled()); //print enrollment: 1

  12. Coding classes and objects: in Course class Course { private String name; private int npeople; private double hours; private String[] clist; public Course(String n) { this.name = n; this.clist = new String[42]; this.npeople = 0; this.hours = 3.0; } public void addStudent(String s) { this.clist[npeople++] = s; } public int numEnrolled() { return this.npeople; } } data members constructor methods

  13. Coding classes and objects: in Course data protection ! class Course { private String name; private int npeople; private double hours; private String[] clist; public Course(String n) { this.name = n; this.clist = new String[42]; this.npeople = 0; this.hours = 3.0; } public void addStudent(String s) { this.clist[npeople++] = s; } public int numEnrolled() { return this.npeople; } } data members constructor the object being constructed methods refers to the object calling the method

  14. Two (or more) objects of the same class… Course c Course c2 public static void main(String[] args) { Coursec = new Course(“cs5”); // constructc c.addStudent(“Michael”); //add a student to c Coursec2 = new Course(“chem”); // constructc2 c2.addStudent(“Marie”); //add a student to c2

  15. Coding classes and objects: in Course class Course { private String name; private int npeople; private double hours; private String[] clist; public Course(String n) { this.name = n; this.clist = new String[42]; this.npeople = 0; this.hours = 3.0; } public void addStudent(String s) { this.clist[npeople++] = s; } public int numEnrolled() { return this.npeople; } } data members constructor methods this is sort of a pain…

  16. thisis optional ! but it is always there… class Course { private String name; private int npeople; private double hours; private String[] clist; public Course(String n) { name = n; clist = new String[42]; npeople = 0; hours = 3.0; } public void addStudent(String s) { clist[npeople++] = s; } public int numEnrolled() { return npeople; } } data members constructor methods

  17. Connect Four For your convenience, the creators of Java’s library have included a Board class that can represent any size Connect Four board... ! 0 0 | | | | | | | | | | | | | | | | | | | | | | | | | | | |X| | | | | |X| |X|O| | | |X|O|O|O|X| |O| --------------- 0 1 2 3 4 5 6 1 1 2 2 3 3 4 4 5 5 0 1 2 3 4 5 6

  18. int int ncols Connect Four: class Board , objectb This is true for sufficiently broad definitions of “the creators of Java’s library” ... char char char char char[][] nrows data Board b char char char char char char char char void addMove(int c, char player) boolean allowsMove(int c)

  19. Board class Board { private int nrows; private int ncols; private char[][] data; public Board(int R, int C) { this.nrows = R; this.ncols = C; this.data = new char[nrows][ncols]; for (int r=0 ; r<this.nrows ; ++r) for (int c=0 ; c<this.ncols ; ++c) this.data[r][c] = ‘ ’; } public void addMove(int c, char player) … public boolean allowsMove(int c) … 3 data members constructor methods Starting code for a Board class and CS5App class is in Hw10Pr1.zip

  20. “Quiz” class CS5App { public static void main(String[] args) { H.pl(“Hi! Welcome to Connect 4…”); int R = H.ni(“How many rows?(4-15)”); int C = H.ni(“How many columns? (4-15)”); Board b = new Board(R,C); char player = 'X'; while (true) { b.print(); int uc = H.ni(player + “'s move:”); while ( !b.allowsMove(uc) ) uc = H.ni(player + “'s move:”); b.addMove(uc,player); if (player == 'X') player = '0'; else player = 'X'; } // end of while } // end of main } // end of class CS5App What is each portion of main doing? 1 2 3 4 What still needs to be done?

  21. 1 2 3 4 “Quiz,” part 2 class Board { private int nRows; private int nCols; private char[][] data; // constructor and other methods here public void addMove(int c, char player) { for (int r=this.nRows-1 ; r>=0 ; --r) { if (this.data[r][c] == ‘ ’) { this.data[r][c] = player; break; } } } public boolean allowsMove(int c) { } } What is each line of addMove doing? Write allowsMove . It should return true if c is OK for a move; false otherwise.

  22. Problem 1 Hw10 Pr1: Connect Four Similar to Lights Out and Life, but using a Board object: class CS5App class Board sets things up and runs a large while loop Board the “constructor” main addMove places a checker • Get the # of rows and cols (R, C) • Create an object, b, of type Board • (3) Big while loop... • Ask for the next player’s move • Check the move & then make it • See if the game is over print outputs to screen Board b = new Board(R,C); allowsMove checks if allowed isFull checks if space left winsFor checks if a player has won

  23. Problem 1 Hw10 Pr1: Connect Four Similar to Lights Out and Life, but using a Board object: class CS5App class Board sets things up and runs a large while loop Board QUIZ the “constructor” main addMove places a checker • Get the # of rows and cols (R, C) • Create an object, b, of type Board • (3) Big while loop... • Ask for the next player’s move • Check the move & then make it • See if the game is over QUIZ print outputs to screen Board b = new Board(R,C); allowsMove checks if allowed isFull checks if space left winsFor checks if a player has won still to do…

  24. Problem 1 Still to write in the Board class: public boolean isFull() 1 public boolean winsFor(char pl) 2 Extra Credit: Mouse input

  25. Problem 2 Hw10 Pr2: The Date Calculator Similar to previous menu problems, but using Date objects: class CS5App Pair Programming Problem Methods sets things up and runs a large while loop main printMenu prints (0) Enter a new date of interest (1) Print the current date of interest (2) Move one day forward in time (3) Move one day backward in time (4) Day difference finder (5) Find the day of the week (9) Quit

  26. Problem 2 Hw10 Pr2: The Date Calculator PAIR Similar to previous menu problems, but using Date objects: class CS5App Methods sets things up and runs a large while loop main printMenu prints (0) Enter a new date of interest (1) Print the current date of interest (2) Move one day forward in time (3) Move one day backward in time (4) Day difference finder (5) Find the day of the week (9) Quit no computer required… Prof. Art Benjamin

  27. Problem 2 Hw10 Pr2: The Date Calculator PAIR Similar to previous menu problems, but using Date objects: class CS5App class Date Methods Methods sets things up and runs a large while loop Date the “constructor” main print prints printMenu prints forward 1 day tomorrow (0) Enter a new date of interest (1) Print the current date of interest (2) Move one day forward in time (3) Move one day backward in time (4) Day difference finder (5) Find the day of the week (9) Quit backward 1 day yesterday isBefore helper method # of days difference between 2 Dates diff diffNoPrint same w/ no printing dayOfWeek returns a String

  28. Two Date objects: d and d2 int day int year int month Date d void print() void tomorrow() int day int year int month Date d2 void print() void tomorrow()

  29. The Date class class Date { private int month; private int day; private int year; public Date(int m, int d, int y) { this.month = m; this.day = d; this.year = y; } public void print() { H.p(this.month + “/”); H.p(this.day + “/”); H.p(this.year); } } data members constructor method

  30. Making a new Date class CS5App { public static void main(String[] args) { Date d = new Date(11,13,2004); Date d2 = new Date(11,25,2004); H.p(“The ACM contest is on ”); d.print(); d.tomorrow(); H.p(“CS 5’s midterm is due on ”); d.print(); H.p(“And Thanksgiving will be ”); d2.print(); } }

  31. Making a new Date class CS5App { public static void main(String[] args) { Date d = new Date(11,13,2004); Date d2 = new Date(11,25,2004); H.p(“The ACM contest is on ”); d.print(); d.tomorrow(); H.p(“CS 5’s midterm is due on ”); d.print(); H.p(“And Thanksgiving will be ”); d2.print(); } } Output 11/13/2004

  32. Making a new Date class CS5App { public static void main(String[] args) { Date d = new Date(11,13,2004); Date d2 = new Date(11,25,2004); H.p(“The ACM contest is on ”); d.print(); d.tomorrow(); H.p(“CS 5’s midterm is due on ”); d.print(); H.p(“And Thanksgiving will be ”); d2.print(); } } Output 11/13/2004 11/14/2004

  33. Making a new Date class CS5App { public static void main(String[] args) { Date d = new Date(11,13,2004); Date d2 = new Date(11,25,2004); H.p(“The ACM contest is on ”); d.print(); d.tomorrow(); H.p(“CS 5’s midterm is due on ”); d.print(); H.p(“And Thanksgiving will be ”); d2.print(); } } Output 11/13/2004 11/14/2004 11/25/2004

  34. tomorrow() int month class Date { public void tomorrow() { } } int int day year data members in every Date

  35. Checking a Date class CS5App { public static void main(String[] args) { // prompt the user for mo, dy, yr: int mo = H.ni(); int dy = H.ni(); int yr = H.ni(); Date d = new Date(mo,dy,yr); if (d.isLeapYear()) H.pl(“d has 366 days”); else H.pl(“d has 365 days”); } }

  36. Leap years int month int int class Date { public boolean isLeapYear() { if (this.year % 400 == 0) return true; if (this.year % 100 == 0) return false; if (this.year % 4 == 0) return true; } } day year only one of these is needed here…

  37. Comparing Dates class CS5App { public static void main(String[] args) { Date d = new Date(11,13,2004); Date d2 = new Date(11,25,2004); if (d.isBefore(d2)) H.pl(“d is earlier than d2”); else H.pl(“d is not earlier than d2”); } }

  38. ComparingDates class Date { public boolean isBefore(Date d2) { } } What two dates are being compared here? d2 is only one of them!

  39. Problem 2 “Tricks” public int diff(Date d); • positive if d is after this • negative if d is before this returns the # of days between this and d • print every day in between! public String dayOfWeek(); returns the day of the week on which this falls

  40. Summary/Examples An object is a variable. Objects are created via new and a constructor. A class is a type of variable. A class can include both data members and methods. The object that calls a method is named this inside that method. Date d = new Date(11,10,2003); class Date { private int month; private int day; private int year; public Date(int m, int d, int y) { this.month = m; this.day = d; this.year = y; } public void print() { H.p(this.month + “/” + this.day + “/” + this.year); } }

  41. Lab this week Last Names A-L Date print tomorrow yesterday isBefore diff diffNoPrint dayOfWeek … • Problem 2: The Date Calculator (Pairs) You’ll need to write (and use) • Problem 1: Connect 4 ! | | | | | | | | | | | | | | | | | | | | | | | | | | | |X| | | | | |X| |X|O| | | |X|O|O|O|X| | | --------------- 0 1 2 3 4 5 6 isFull winsFor allowsMove • Extra Credit: Mouse input-handling for Connect Four

  42. Example contest problem Factorial Factors - Southern California Regional ACM Programming Contest The factorial function, n! = 1 · 2 · ... · n, has many interesting properties. In this problem, we want to determine the maximum number of integer terms (excluding 1) that can be used to express n!. For example: 8! = 1 · 2 · 3 · 4 · 5 · 6 · 7 · 8 = 2 · 3 · 2 · 2 · 5 · 3 · 2 · 7 · 2 · 2 · 2 = 27 · 32 · 5 · 7 By inspection, it is clear that the maximum number of terms (excluding 1) that can be multiplied together to produce 8! is 11. The input for your program consists of a series of test cases on separate lines. Each line contains one number, n, 2 <= n <= 1000000. For each test case, print the maximum number of factors (excluding 1) that can be multiplied together to produce n!. Put the output from each test case on a separate line, starting in the first column. Sample Input 2 1000000 1996 5 8 123456 Sample Output 1 3626619 5957 5 11 426566

  43. Objects An object is a data structure (like an array), except (1) Its data elements need not be the same type. (2) Its data elements have names chosen by the programmer. (3) Its data can be protected from unauthorized changes! (4) An object can have behaviors built-in by the programmer. int double hours number String Course c name String String[] String students the dot is used to get at parts of an object (data or actions) void addStudent(String s) int numStudents() Names!

  44. slides to print following this…

  45. Gaussian Elimination public static void solve(double[][] A) { for (int c=0 ; c<A[0].length-1 ; ++c) // columns { multRow( A, c, 1/A[c][c] ); // diag = 1.0 for (int r=0 ; r<A.length ; ++r) // rows { if (c != r) // off-diagonal elements become 0.0 { addMxRaToRb( A, -A[r][c], c, r ); } } } } dest row multiplier dest row source row multiplier

  46. Objects An object is a data structure (like an array), except (1) Its data elements need not be the same type. (2) Its data elements have names chosen by the programmer. (3) Its data can be protected from unauthorized changes! (4) An object can have behaviors built-in by the programmer. int double hours npeople String Course c name String String[] String clist void addStudent(String s) int numStudents() Names!

  47. Coding classes and objects: in main int double hours npeople data String name Course c … String String[] String clist Course(String name) “constructor” void addStudent(String s) methods int numEnrolled() public static void main(String[] args) { Coursec = new Course(“cs5”); // constructc c.addStudent(“Michael”); //add a student H.pl(c.numEnrolled()); //print enrollment: 1

  48. Connect Four For your convenience, the creators of Java’s library have included a Board class that can represents any size of Connect Four board... ! 0 0 | | | | | | | | | | | | | | | | | | | | | | | | | | | |X| | | | | |X| |X|O| | | |X|O|O|O|X| |O| --------------- 0 1 2 3 4 5 6 1 1 2 2 3 3 4 4 5 5 0 1 2 3 4 5 6

  49. “Quiz” class CS5App { public static void main(String[] args) { H.pl(“Hi! Welcome to Connect 4…”); int R = H.ni(“How many rows?(4-15)”); int C = H.ni(“How many columns? (4-15)”); Board b = new Board(R,C); char player = 'X'; while (true) { b.print(); int uc = H.ni(player + “'s move:”); while ( !b.allowsMove(uc) ) uc = H.ni(player + “'s move:”); b.addMove(uc,player); if (player == 'X') player = '0'; else player = 'X'; } // end of while } // end of main } // end of class CS5App What is each portion of main doing? 1 2 3 4 What still needs to be done?

  50. 1 2 3 4 “Quiz,” part 2 class Board { private int nRows; private int nCols; private char[][] data; // constructor and other methods here public void addMove(int c, char player) { for (int r=this.nRows-1 ; r>=0 ; --r) { if (this.data[r][c] == ‘ ’) { this.data[r][c] = player; break; } } } public boolean allowsMove(int c) { } } What is each line of addMove doing? Write allowsMove . It should return true if c is OK for a move; false otherwise.

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