A Revamping Of our skills so far

Our Tools so Far Variable - a placeholder for a value Method - a set of code which accomplishes a task Class - a mold for an object Object Instance - a variable which holds an object value If statement - alters flow of control based on boolean condition(s)

Variables -Have a type, name, and value int size = 5; Ball myBall = new Ball(50, Color.RED, 6); - Two kinds: Instance Variables and Local Variables typename value typename value

LOCAL VARIABLES -declared and defined w/in a method -can’t be accessed outside this method public class Tire { public Tire(){ int radius = 40; } public int getRad(){ return radius; } } X ‘radius’ is local to the constructor method and therefore can’t be accessed in this method INSTANCE VARIABLES -declared outside any methods (still w/in class) -can be accessed anywhere in the class -use the private keyword -should start with underscore public class Tire { private int _radius; public Tire(){ _radius = 40; } public int getRad(){ return _radius; } }

Methods -Block of code which can be called/executed public double average (double num1, double num2){ double sum = num1 + num2; double average = sum / 2.0; return average; } -always public -can have as many parameters as you want (including none) -use return type of void if method won’t return anything Modifier Return Type Method Name Parameters

void return type - Sometimes methods don’t need to return (output) anything - But every method needs to declare a return type public void greeting (boolean isMale){ if(isMale){ System.out.println(“Hello Sir”); } else{ System.out.println(“Hello Maam”); } } - note the lack of a return statement, void makes this fine!

Main Method This is where every java program starts One main method per program Looks like this: public static void main (String [] args){ //your java program starts here }

Classes The mold for our object instances Made up of two things: Instance Variables – model properties of the class Methods – model abilities of the class

Our Classic Ball Example public class Ball { //instance variables go here private int _size; private java.awt.Color _color; private int _bounciness; public Ball(int size, java.awt.Color color, int bounciness){ //this is the constructor method _size = size; _color = color; _bounciness = bounciness; } //here’s a method public void setSize(int newSize){ _size = newSize; } }

Object Instances Create one: Ball myBall = new Ball(60, Color.BLUE, 11); Call methods on it: myBall.setSize(30);

Now Something Random Many times you want to be able to create some randomness Java has a few solutions, here’s one: Random rand = new Random(); int randInt = rand.nextInt(5); A Java library object A method of the Random class randInt will be between 0 and 4

Call to Action Coding is inherently time-consuming You’ve been doing great work in lab But becoming a prolific coder will take more than 1.5hr/week You know enough to start embarking on your own projects outside of lab Dream big and start small Don’t be intimidated, you CAN do it! Stick with it!