Warm-up: Tuesday, March 11

1. Warm-up: Tuesday, March 11 • In programming, what is the difference between an object and a class?

2. Objects and Classes PAP Computer Science Cycle 5

3. Review: Output/Input • Output • System.out.println( ); • Input • int number = console.nextInt( ); • double decimal = console.nextDouble( ); • String word = console.next( );

4. Classes • Characterize an object • Category of information used to collect and contain properties/methods for related pieces of information • Objects are one instance of that class

5. Example Class: Superheroes • Class properties • Name, costume, colors, sidekick, main villain, powers, universe (Marvel vs DC) • Class methods • Fly, use a super power, talk, rescue a damsel in distress • Object instances • Superman, Spiderman, Wolverine, Flash

6. Jeroo Connection • Class properties • how many flowers is it holding, what direction is it facing • Class methods • hop( ), plant( ), pick( ), toss( ), turn( ), give( ) • Object instances • Jeroobobby = new Jeroo

7. Classes We’ve Seen So Far • String • String word = “some text”; • Scanner • static Scanner console = new Scanner(System.in)

8. Creating an Object • Recall…an object is an instance of a class Standard format: Class name = new Class(parameters) Example: Jeroo bobby = newJeroo(2);

9. Keyword New • The keyword new is used when creating objects • It sets aside memory in the computer for the object • It only has to be used once per object creation, much like declaring a variable

10. Using an Object – Dot Operator • To access the properties and methods associated with a class, you first type the name of your object, followed by a dot (.), then put the command you want to run Jeroo bobby = new Jeroo( ); //create object bobby.hop( ); //use the object

11. Examples static Scanner console = new Scanner(System.in); int number = console.nextInt( ); String name = “Spring Break”; int length = name.length( ); float circumference = 2*radius*Math.PI

12. Review • Classes are a way to bundle the properties and methods of related information. • Class objects are instances of a class. • Use the operator new to create a class object. • In Java, the dot (.) separates the object name from the property or method name

13. Warm-Up: Wednesday, March 12 • What is the difference between class properties and class methods?

14. Class Math Cycle 5 Week 4

15. Review • Classes are a way to bundle the properties and methods of related information. • Class objects are instances of a class. • Use the operator new to create a class object. • In Java, the dot (.) separates the object name from the property or method name

16. Math Operators • Basics • Addition (+) • Subtraction (-) • Multiplication (*) • Division (/) • Modulus (%) • Other math functions must be accessed using the Math class

17. Using class Math • The class Math is stored within the java.lang package • At the beginning of each code, be sure to add the following line: import static java.lang.Math.* • This allows you to drop the Math. prefix when using Math methods and constants

18. Math Constants • Math.E = 2.718281828459045 • Math.PI = 3.141592653589793

19. Math Methods • abs(x) – absolute value abs(-96.5)  95.6 • ceil(x) – ceiling operator ceil(54.13)  55 • floor(x) – floor operator floor(54.13)  54 • exp(x) – returns ex exp(3)  e3  20.0855369232

20. Math Methods • log(x) – natural logarithm (base e) of x log(2)  ln(2)  0.69314718056 • log10(x) – base-10 logarithm of x log10(100)  log10(100)  2.0 • max(x,y) – maximum of two numbers max(15, 25)  25 • min(x,y) – minimum of two numbers min(3, 4)  3

21. Math Methods • pow(x,y) – returns xy pow(2,3)  23  8 • round(x) – rounds x to the nearest whole # round(34.4)  34 round(34.7)  35 • sqrt(x) – square root of a number sqrt(121)  √121  11

22. import static java.lang.Math.*; public class MathProblems { public static void main(String[] args) { int x = pow(10, 3); System.out.println(“10^3 = “ + x); int m = max(24, 67); System.out.println(“Max of 24 and 67 = “ + m); double a = 2*PI*4; System.out.print(“Area of a circle with radius ”); System.out.print(“of 4 = “ + a); } }

23. Warm-up: Thursday, March 13 • What class are each of these packages associated with? • java.util.* • javax.swing.* • java.lang.Math.*

24. Warm-up: Thursday, March 13 • What class are each of these packages associated with? • java.util.* Scanner • javax.swing.* JOptionPane (pop-up boxes) • java.lang.Math.* Math

25. Class String Cycle 5 Week 4

26. Strings - Review • Class used to manipulate character arrays, or words • Declared like variables • String name = “Alexander”; • Can be combined using the + operator • String break = “Spring ” + “break”;

27. String Methods • String.length( ) – returns the length of the string (how many letters long it is) • String word = “dog”; word.length( )  3 • String.toLowerCase( ) – changes all capital letters to lowercase • String word = “HAHA”; • word.toLowerCase( )  “haha”; • String.toUpperCase( ) – changes all lowercase letters to capital letters • String word = “kitty”; • word.toUpperCase( )  “KITTY”

28. Strings as Lists • Strings are essentially a list of letters • Strings are indexed just like lists • String indices begin counting at 0 String word = “happy”; word[0] = ‘h’ word[1] = ‘a’ word[2] = ‘p’ word[3] = ‘p’ word[4] = ‘y’

29. More String Methods • String.charAt(x) – returns the letter at position x in the String • String word = “happy”; • word.charAt(2)  ‘p’; • String.replace(x,y) – replaces each instance of character ‘x’ with character ‘y’ • String word = “happy”; • word.replace(‘p’,’ r’)  “harry”

30. indexOf( ) • indexOf(char) – returns the index, or list location, of the first instance of letter char • String word = “happy”; • word.indexOf(‘h’)  0 • indexOf(str) – returns the index, or list location, of the first instance of a String str • String name = “Alexander”; • name.indexOf(“and”) 4 • Note: Both of these commands will return -1 if the character or String is not found

31. String.substring( ) • String.substring(x, y) – Converts the characters between list location x of the String (inclusive) and list location y of the String (exclusive) into a new String • String word = “Spring Break”; • word.substring(0,6)  “Spring” • word.substring(7, 12)  “Break” • word.substring(3, 9)  “ing Br”