1. Newport Robotics Group 1 Tuesdays, 6:30 – 8:30 PM Newport High School Week 4 10/23/2014

2. So we have the foundation needed to move on to new things! 2 Review of Week 3

3. Readability

4.  You can’t change the value.  Use the key-word final.  Uses a different naming convention.  Helps readability.  Instead of:  int num2 = num1 + 7;  final int NUM2MODIFIER = 7; int num2 = num1 + NUM2MODIFIER;

5.  To improve readability, you can often remove repetitive code, for example:  Instead of: double quadratic1 = (-b + Math.sqrt(b*b – 4*a*c))/(2*a); double quadratic2 = (-b - Math.sqrt(b*b – 4*a*c))/(2*a);  Use: double root = Math.sqrt(b*b – 4*a*c); double quadratic1 = (-b + root)/(2*a);

6.  A method is overloaded if there are two or more methods with the same name, but different data types for the parameters and/or number of parameters  Allows a method to perform similar tasks with different inputs  Example: The System.out.println method is overloaded so it can print different types of data: Strings, ints, booleans, doubles, etc. 6

7.  Say we have two methods: public static double mean(int a, int b) { … } public static double mean(int a, int b, int c) { … }  The compiler will match up a method call to the correct method implementation based on the count and types of the given parameters  mean(2, 3) will call the first method  mean(5, 7, 1) will call the second method  mean(1) will result in an error, as there is no matching method for mean(int)  mean(1.0) will also be an error: no method mean(double) 7

9.  Primitives store by value  Objects store by reference  A reference says where the object is in memory: the actual object is somewhere else  In this example, a stores the value of the int, 25, while s stores the address of where the String object is in memory, 83. 83 is NOT the value of the String! 9 int a 25 String s 83

10.  Stores variables in objects  Looks like: access static type name; i.e. private double GPA;  Assigned values in constructor, mutator methods  Accessed by accessor methods, or is public.

11.  Used to create new objects.  Looks like: public ClassName(parameters) { varName1 = myVarName; }  Called by:  ClassName name = new ClassName(parameters);

12.  Does things:  Looks like: access static returnType name(parameters) { //code goes here }  Called by: objectName.methodName(parameters);

13.  Accessors access values, returning instance variables / other values.  Mutators mutate values, modifying an instance variable in the object.

14.  static refers to whether the method or variable belongs to the class, and is the same, or static, throughout all instances of the class.

15.  Now that we know how to use classes, we’re going to test them, without a main method directly inside the class.  Is another class that is usually called ClassNameTester.

16.  Testers contain a main method, then construct an object of the class it is testing.  It then uses the methods to test and see if it works.

17.  What variables would our cow need to store?  weight – a double  isAwake – a boolean  What methods would our cow need to do?  getWeight  getAwake  eat  wakeUp  goToSleep  getMilk

18.  Instance Fields: // how much the cow weighs in pounds private double weight; // true if the cow is awake; false if the cow is sleeping private boolean isAwake;  Constructor: public Cow(double theWeight, boolean awake) { weight = theWeight; isAwake = awake; }

19.  Methods: public double getWeight() { return weight; } public boolean isAwake() { return isAwake; }

20. public void wakeUp() { isAwake = true; System.out.println("streeeeetch..."); } public void goToSleep() { isAwake = false; System.out.println("zzzzzz..."); }

21. //This method milks the cow for a given number of seconds. We assume that each //gallon of milk weighs 7 pounds, and that a cow will give one gallon of milk per minute of //milking. It is not terribly realistic in that it lets you convert the entire weight of the cow //into milk, but we're dealing with virtual cows here, so whatever... public double getMilk(int seconds) { // we cannot get milk from a cow if it is asleep! if (!isAwake) return 0.0; //compute the max # of gallons the cow can give double gallonsToGive = weight / 7.0; //compute the # of gallons we want from the milking time double gallonsWeWant = seconds / 60.0; // We actually get the minimum of those two values double gallonsWeGet = Math.min(gallonsToGive, gallonsWeWant); weight -= gallonsWeGet * 7.0;// adjust the cow's weight return gallonsWeGet;// return the milk }

22.  Tester: public class CowTester { public static void main(String[] args) { // bubba is born (we create a new object of type Cow) Cow bubba = new Cow(445.0, false); bubba.wakeUp(); // bubba eats 35 pounds of feed bubba.eat(35.0); // milk bubba for 4 mins (240 secs) double gals = bubba.getMilk(240); System.out.println("Bubba gave us " + gals + " gallons of milk!"); bubba.goToSleep(); System.out.println("Bubba now weighs " + bubba.getWeight() + " pounds."); }

23.  Make a class box with instance variables length, width, height, isOpen, and material(String).  It should contain accessors/mutators for all of the above, and the methods getVolume, getSurfaceArea, and toString, which returns a String representation of the box.  Also, make a tester.

24.  Create a class Tuple that does the following  A constructor with two parameters for first and second.  Has 2 integer parameters, first and second that can be accessed publically.  Has a method that returns the product of the two numbers  Has a method that returns the larger of the two numbers  Has a method that takes in another tuple and adds that tuples’ first to its first and that tuples’ second to its’ second. 24

25.  Create a class dayIn2014  The class with have instance variables day and month, and static variable year.  Create constructor that takes a month and date as parameters  Create assessors and mutators methods for all changeable variables  Create a static method that take in two dates as parameters and returns true if the first date is earlier than the second and vice versa 25

26.  Create a class coordinate  Should have two values, x and y.  Have a constructor  A method that calculates the distance from the origin  Accessor methods for x and y.  Mutator methods addToX and addToY that increase the value of X and Y by the parameter. 26

28. Time to move on! 28

29. Interfaces

30.  Inheritance is when a class takes all the methods and variables of another class(superclass) for itself and adds methods and variables that weren’t in the original.  Each class can have one superclass, and an infinite amount of subclasses.  You implement a subclass by adding extends ClassName in the class declaration  For Example:  public class MountainBike extends Bicycle

31.  Class Vehicle What variables? ▪ weight ▪ wheels ▪ Miles ▪ On or off  What methods? ▪ drive(distance)

32.  Create a subclass of Vehicle (maybe Car, Bike, Truck?) with its own methods/variables e.g.  turnOn()  refuel()  miles per gallon  yPos  Etc.

33.  Interfaces are a way to create a standard to how different classes interact  Interfaces can only contain constants, method signatures, and nested types  Interfaces have empty methods that are only declared. These are called abstract methods.  Interfaces are implemented in classes or extended in other interfaces  For example:  public class MountainBike implements Wheeled

34.  All of an interfaces methods are abstract  An Abstract class has at least one method that is non abstract 34

35.  Interface Teleportable  What method(s)?  teleport(double newX)

36.  Create a new class that extends your vehicle subclass, and implements the teleportable interface.