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With help fromhttp://docs.oracle.com/javase/tutorial/java/javaOO/classvars.html

Refers to the instance of the class that is running the code right now

Static methods have no “this” because they run the code from the Class, itself

http://docs.oracle.com/javase/tutorial/java/javaOO/thiskey.html

This inside the class code that has an

instance

First create a variable to hold an instance MyClass x ;

Then fill it with an instance by calling constructor x = new MyClass(1);

Access its public variables with : x.myvar1

Access its methods: x.myMethod(‘a’);

Using Objects (such as in your main routine)

Just as arrays passed to methods are really just passing a pointer to the array, objects pass only pointers.

When your main method calls mymethod(player1), it is updating the Player object player1 inside the main method.

Note: Strings act like primitives and pass real copies (not under the covers, but they act as if they do)

Passing Objects

Why? When other programmers use your class, you must not change anything public or you will break their code. Ex: Fang – if we have a game using advance(), and Fang

upgrades to insist on advance(int y), all our code breaks How?

Public – everyone Private – no one Protected – extended can Nothing - your package (your bluej panel) can Method or Variable

http://docs.oracle.com/javase/tutorial/java/javaOO/accesscontrol.html

Encapsulating

Static – just like method static – one per class Ex: Class variable total # of bikes

static int numbBikes = 0; (defaulting to 0) each bike instance points to that one variable # of bikes.

Can change if your program asks it to numbBikes = numbBikes + 1; Changes the total number for all the bike instances , not just the

one you are accessing. Without static – a separate value for each instance

Ex: speed, color of a bike int speed = 0;

Constants Make it unchangeable with the word final after static Capitalize by convention

ex: maximum number of bikes: static final int MAXBIKES = 15; Cannot later have MAXBIKES = MAXBIKES+1;

http://docs.oracle.com/javase/tutorial/java/javaOO/classvars.html

Class Variable

Arrays can hold objects If a point has a x and y, an array of 3 points holds 3

point objects, each with their own x and y. Point[] p = new Point[2]; // makes 2 player miniboxes p[0] = new Point(1,2); // puts a point object into p[0] p[1] = new Point(3,4); // puts a point object into p[1] p[0].getDistance(p[1]); // asks p[0] for its distance

from p[1] See in debug

Arrays holding objects

Do these exercises, but your deck of cards should only have the face cards so you have less coding. JQKA

http://docs.oracle.com/javase/tutorial/java/javaOO/QandE/creating-questions.html

Exercises

Do question #1 and Exercise 1 & 2. (Skip the garbage collection questions.)

http://docs.oracle.com/javase/tutorial/java/javaOO/QandE/objects-questions.html

Exercise 2

Shortcut for loop through an array: for (variable to hold value : array name) Ex:

int[] arr= {1,2,3,4};int tot = 0;for (int x : arr){ tot = tot + x;}System.out.println(tot);

More on Arrays – For Each