Chapter 9 Arrays

What is an Array An array is a special variable, which can hold a collection of elements of the same type. Examples: A list of colors A list of objects, such as rain drops or cars A list of players in a game A sequential list of numbers to link to/associate with other variables such as x, y, w, h, color, etc.

Characteristics of Arrays Arrays start with 0. Arrays have a fixed size. Each element in an array has a unique position, in which the order is crucial. Each index/position of an array is matched with an element. E.g. array of your siblings you might be #2. The size can be: -A number -A variable of int type -An expression that calculates an integer

Declaring and Initializing Arrays Declaring: int [] myArray; String [] myWord = new String[6]; Declaring and initializing with values : float[] myNums = { 1.0, 3.2, 6, 9.5};

…from processing.org/tutorials/arrays, an easier way to remember array declarations   // Declare int[] data;   // Create data = new int[5]; // Assign data[0] = 19; data[1] = 40; data[2] = 75; data[3] = 76; data[4] = 90; // Declare & create int[] data = new int[5]; // Assign data[0] = 19;   data[1] = 40; data[2] = 75; data[3] = 76; data[4] = 90; // Declare, create, assign int[] data = { 19, 40, 75, 76, 90 };

Examples of specifying size color [] swatches = new color[4]; int [] storeLoc = new int [12 ]; int cities = 5; string [] mycities = new string [cities]; int [] family = new int [siblings+parents]

In summary, 3 ways to fill with value (initialize) Hard code the values in each spot. Type out a list in curly brackets separated by commas. Iterate through the elements in an array. See next slide…

Table: Three ways to initialize Hard code the values in each spot   String [] stuff = new String [4]; stuff[0] = "Buick"; stuff[1] = "Nissan"; stuff[2] = "Toyota"; stuff[3] = "Ford"; Type out a list in curly brackets separated by commas. String [] siblings = {"Ernest", "Mary", "Therman"}; The above two methods are inefficient for large arrays. The third option is most widely used. Also, there are more advanced ways such as filling with data from a text file. Iterate through the elements in an array. This also allows you to access each index value. for(int i = 0; i < stuff.length; i++ { }

Accessing elements in Arrays Several ways… Iterating through each element is one of them. See examples 9-5, 9-6, and 9-7. Then do #7

Create a Bar Chart Remember https://processing.org/tutorials/arrays? Let’s do again. Then remix your own way.

Time for Fun Programming again #54 https://www.funprogramming.org A bit of a remix with names and descriptions of computer company founders

Do It Yourself: Create a String array with about 5 names of family members. Iterate through each. If time permits, use a for() to place a rectangle around each name. println() or text() to see results (See solution at moorec.people.cofc.edu/fam.txt)

I started my own homework…

Jitterbug Just another example. Nothing spectacular, but you can gain more experience on synthesizing current and past knowledge. Jitterbug[] bugs = new Jitterbug[10]; void setup() { size(240, 120); for( int i = 0; i< bugs.length; i++) { float x = random(width); float y = random(height); int r = i*2; //i did a remix here bugs[i] = new Jitterbug(x, y, r); } void draw() { for(int i = 0; i<bugs.length; i++){ bugs[i].display(); bugs[i].move(); Main program on left and class on right.

Create class without looking: Since we ran out of time, ignore the steps on these two pages. Instead we will open example 9-11. Then study and modify it. Create class without looking: The class is called Ball The data is: float x for horiz position float y for vert position float w for width of circle The method functions as follows: Fills with a color No stroke Draws an ellipse with x, y, w, w arguments

Continue Incrementally: Now pretend you only want an array that displays 3 balls. No movement, no gravity. Modify page 181 to only display 3 balls from an array.