CSE 113 Week 4 February 4 - 8, 2008 Monday Announcements Software Installation Fest 2/5 & 2/6 4-7 in Baldy 21 Exam 2 is 2/6 Module 1 due 2/8 Module 2 due 2/15 Exam 3 is 2/15 Module 3 due 2/22 Wednesday Announcements Software Installation Fest 2/6 4-7 in Baldy 21 Exam 2 TODAY! Module 1 due 2/8 Module 2 due 2/15 Exam 3 is 2/15 Module 3 due 2/22 Friday Announcements Module 1 due 2/8 (TODAY!) Module 2 due 2/15 Exam 3 is 2/15 Module 3 due 2/22 Monday Another look at this bit of code: Turtle t1 = new Turtle(); Turtle t2 = new Turtle(); t1 = t2; Both t1 & t2 refer to the same turtle and the turtle that was referred to by t1 is no longer accessible in the program. Monday We can actually modify the turtle’s source code to include methods that we define. We need to open up the Turtle.java file in the editor pane and find where the methods should go. Then we can write our own method definitions. Monday Method definitions look like this: public returnType methodName (parameter list) Where the return type is the type of information we want to get back from the method (or void if there is none) The parameter list tells us what additional information we need to complete the job of the method. Wednesday We can have our turtle do turtle things, like drawing squares and lines Or we can have our turtle bring up a dialog and we can create a picture from what the user chooses. (This might be a little strange to have a turtle do this.) Wednesday Java source code files contain class definitions, that’s why there is code that says public class Name Wednesday In DrJava, comments in files come up green. Comments are parts of the file added by the programmer to explain what the code does. They are usually written in English (or some other natural language) and are ignored by the compiler. Wednesday At the top of the file before the part where it tells us to add in our own method definitions, we see the definitions of the constructors for the class. Remember, we call the constructors with new when we are creating an object. Friday Pictures are made up of a grid of pixels. Each pixel is encoded as a triple of numbers that represent the amount of red, green, and blue the pixel should display RGB values range from 0 to 255. We can display over 16 million different colors with this encoding. Friday We can call explore() on a picture object to allow us to zoom in or out, or see the particular color value at a pixel location. We can get a Pixel object from a spot in the Picture grid, and then we can change its color or even just its red, green, or blue component.